Methodology to determine fungicide efficacy ratings for the EuroBlight tables – potato late or early blight

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Evenhuis, R.A. Bain, I.K. Abuley, H. Hausladen, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6305294/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 13 Mar, 2026 Read the published version in Potato Research → Version 1 posted 6 You are reading this latest preprint version Abstract Late blight (Phytophthora infestans ) and early blight (Alternaria solani) are the most important diseases in potato cultivation. The control of these diseases depends largely on fungicide sprays during the growing season. Fungicides differ in their efficacy to control any pathogen. The use of effective fungicides is necessary for both the control of the disease and to avoid unnecessary sprays. Each active ingredient has its own efficacies and specific characteristics, which are expressed in fungicide products. A EuroBlight fungicide table was set up to provide an overview of the relative ratings for each characteristic for different fungicides used to control late blight or early blight. Until 2007 EuroBlight fungicide ratings were based on the judgement of experts from the crop protection companies and independent researchers. To objectively evaluate the effectiveness of fungicides, harmonised protocols were discussed, and it was proposed that the ratings of fungicides for the EuroBlight fungicide table were to be calculated, based on results from field experiments carried out over 2 years and in at least 3 European countries. Fungicide ratings derived from the experiments, which indicate the efficacy of fungicides to control potato late blight (foliar and tuber blight) or early blight, were published on the EuroBlight website from 2008. This paper describes the experimental procedure as well as statistical analyses used to derive the EuroBlight fungicide ratings. The procedure allows ratings to be calculated even although candidate fungicides are tested in different years. Overall, the method developed and validated in this study is robust and provides an objective procedure for deriving numeric ratings for fungicides, not just for potato late blight and early blight, but also for other host-pathosystems. Phytophthora infestans Alternaria solani Solanum tuberosum crop protection Introduction The oomycete Phytophthora infestans is the causal organism of potato late blight, the most important disease in potato cultivation in northwestern Europe with its maritime climate (Haverkort et al., 2008 ). Early blight, caused by Alternaria solani , is more important in eastern and south Europe, where the weather is characterized as a continental climate, although the pathogen is found ranging from tropical conditions to a temperate climate (Ellis & Gibson, 1975 ). Fungicides play a crucial role in the integrated control of both late blight and early blight. Typically, fungicides are sprayed on a weekly basis to control these diseases, given the explosive nature of both. As an example, in the Netherlands the average number of sprays to control potato late blight per season varies from 7 to 20 depending on the weather, disease pressure and resistance level of the potato variety (Schepers et al. 2009 ; Cooke et al. 2011 ). Whilst early blight is primarily a foliage disease, late blight attacks every part of the plant (e.g. leaves, stems, tubers). Therefore, it is important to use fungicides that effectively protect the leaves (early blight and late blight) as well as other plant parts such as tubers and stems (in the case of late blight). Each active ingredient has its own efficacies and specific characteristics, which are expressed in fungicide products. A EuroBlight fungicide table was set up to provide an overview of the relative ratings for each characteristic for different fungicides used to control late blight or and early blight. Until 2007 the EuroBlight ratings of the fungicides were based upon the judgement of experts from crop protection companies and independent researchers. However, this method was subjective and not based on standardized methodology. Accordingly, there was as a need to develop a more robust and objective method to evaluate the fungicides. Towards this aim, harmonised protocols were discussed among EuroBlight members, and it was proposed that the ratings of fungicides to control potato late blight (foliar and tuber blight) and early blight for the EuroBlight table were to be calculated based on results from field experiments carried out over 2 years and in at least 3 European countries. The objectives of this paper were to describe the method developed for rating the fungicides used for controlling late blight and early blight and to demonstrate its usefulness. Materials and methods General aspect of the experiments Field experiments were carried out to rate fungicides for controlling late blight on leaves (foliar blight) and tubers (tuber blight), and early blight. The experiments were conducted in Denmark, Germany, the Netherlands and United Kingdom. Foliar blight experiments were carried out in eighteen consecutive years (2006 to 2023). However, in some years tuber blight or early blight experiments were not requested (Table S1). For the foliar blight and tuber blight ratings in Table 1 , only the fungicides registered in the EU in 2025 were used for the calculations. For early blight a limited number of fungicides was tested, and all were used for the calculations. In general, the trials conformed to local good agricultural practice. The exception was that many consecutive fungicide sprayings of the same product were carried out in a weekly scheme for late blight and in a weekly or fortnight scheme for early blight. The experiments were carried out in accordance with GEP. The cultivars planted were either susceptible to P. infestans or A. solani and were popular in the country in which the experiment was carried out. Plot size varied, depending on the experiment, but with a minimum of four rows. The minimum net plot consisted of 2 rows with a length of 8 m based on the EPPO protocols for late blight (Anonymous, 2020 ) and early blight (Anonymous, 2008 ). All experiments were arranged as randomized complete block designs with four, or sometimes five, replicates. In the late blight experiments, no untreated plots were included in the trial to avoid uneven disease pressure. To promote uniform disease pressure, untreated spreader rows of a susceptible variety were planted alongside the plots. The initial protocol for foliar blight is published on the EuroBlight website (Schepers et al., 2007 ) There is also a protocol for tuber blight experiments (Bain et al., 2009 ). In the Netherlands potato late blight trials were surrounded by a maize barrier since it this is required by law. In the early blight trials untreated plots were part of the experiment and were randomly allotted. Details are described in the Alternaria protocol (Evenhuis et al., 2019 ). Fungicide applications To be able to compare results obtained in different locations and years, reference treatments were included in the trials. In the foliar blight and tuber blight trials the reference treatment was mancozeb sprayed at 1500 g a.i./ha. In the early blight trial, the reference treatment was the untreated control. Fungicide applications were carried out by tractor-mounted or tractor-pulled sprayers. Spray volume varied from 200 to 400 l/ha and a pressure of 3 bar, depending on the trial location. In the foliar blight experiment spray applications were carried out with an interval of 7 days ± 1, depending on the weather conditions. The first application was done before the first infection so that the treatments were initially preventative. For the tuber blight experiments, in the rapid canopy phase cover sprays were applied. The choice of fungicide was left to the trial manager, but not one with high efficacy in controlling tuber blight. Until mancozeb was banned in the EU, usually this active ingredient was used, sometimes together with cymoxanil. The objective of the tuber blight control experiments was to compare the efficacy of fungicides in minimising the incidence of tuber blight through a direct effect, i.e. ‘activity against tuber infection as a result of fungicide application after infection of the haulm, during mid- to late-season when there is a direct effect on the tuber infection process’. Starting the test fungicides when the foliar blight severity reached approximately 0.5%, the candidates were sprayed at intervals of 7 days, with permitted variation of ± 1 day depending on the weather conditions. For the early blight experiments, fungicide applications were carried out with 7- or 14-day intervals. The fungicides to be tested were sprayed multiple times consecutively, overriding label stipulations to avoid this for fungicide resistance management. For early blight and tuber blight, the first fungicide application was usually 6–8 weeks after emergence. Fungicides were sprayed at the highest dose rate registered in Europe. When fungicides were not yet registered the expected highest dose rate was sprayed. In the early blight trials late blight was managed by using fungicides that had no efficacy against A. solani. Inoculation The details below are a summary of the methodologies used in the four countries. It should be noted that there was minor variation in some details between sites. In the foliar and tuber blight trials, spreader rows were planted alongside the fungicide plots. These spreader rows were not sprayed against potato late blight. Next to each plot one potato plant in the spreader row was inoculated with P. infestans. The P. infestans genotypes used depended on the year and location of the experiment. Genotypes frequently used in all countries were EU-13-A2 and EU-36-A2; sometimes 6_A1 (UK only). For some trials inoculum was prepared as described in Abuley and Hansen ( 2021 ): (1) mycelial plugs of the P. infestans isolates were transferred to rye B agar media and incubated under fluorescent light at 17 ± 2°C (Denmark) or 15°C elsewhere; (2) detached leaves of the late blight-susceptible cultivar Bintje were inoculated with a sporangial suspension from step one. Sporangia formed on the leaves were harvested and adjusted to 10000 sporangia/ml for inoculating the spreader-row plants. Inoculation was sometimes performed in the evening when relative humidity was high, spraying approximately 10 ml of inoculum per potato plant. Extended leaf wetness was achieved by irrigating the entire field before inoculation. If weather conditions were unsuitable, inoculation was postponed until the next day, or inoculated plants were sealed in polythene bags, which were removed early the next morning. For some trials there was also natural infection at some point during the growing season. In later trials the genotype composition of the P. infestans population in the trial field was recorded. Inoculation of the Alternaria solani experiments was optional. In Germany infection usually relied on natural inoculum sources. In Denmark and the Netherlands trials were inoculated by broadcasting barley (Denmark) or wheat (the Netherlands) kernels, that had been infected by A. solani , between the potato ridges thus increasing the disease pressure. Subsequent infection of the trial relied on natural weather conditions. Sprinkler irrigation To enhance the development of late blight when conditions were not favourable, sprinkler irrigation was applied. In the Netherlands sprinkler irrigation was carried out from 22:00 to 02:30 and from 05:00 to 08:30. Each hour the sprinklers ran for 1 minute. For some tuber blight experiments irrigation was applied to the blighted trial. This was normally 1 day after fungicide application. The water volume applied varied from 10 to 20 mm. Irrigation was omitted when natural precipitation was sufficient to transfer spores from the haulm to the progeny tubers. Disease assessment During the growing season potato late blight severity (percentage foliage destroyed by P. infestans ) was assessed visually at weekly intervals, both in the foliar blight and tuber blight experiments. The last assessment had to be within 7 days of the final application of fungicide for that data to be included in the calculation of a rating. In the early blight trials disease severity was visually assessed weekly from the onset of first symptoms in the untreated control until the crop was completely senescent. A trial was considered successful if the disease severity of the worst treatment, including the reference, was ≥ 10%. To facilitate statistical analysis, the standardized area under the disease progress curve (StAUDPC) was calculated for both late blight and early blight (Campbell and Madden 1990 ). The StAUDPC is a standardized version of the area under the disease progress curve (AUDPC), which allows comparisons of epidemics of varying duration. Harvesting of tubers and tuber blight assessment At the end of the growing season the haulm (leaves plus stems) of the tuber blight trials was killed using a herbicide desiccant. Harvest of the tubers did not take place until all of the leaves and stems had been completely dead for at least 2 weeks. Progeny tubers were harvested from the middle two rows. Tuber samples (35–50 kg / plot) were taken for each treatment for subsequent assessment. The target number of tubers to be assessed per treatment was 1600. To reduce the risk of tuber infection during harvest further, tubers were dried quickly under ventilation from the day of harvest. Tuber blight assessments were made shortly after harvest and again after incubation in a non-refrigerated store for about 3 weeks to 3 months. Both number and weight of the blight-free and blighted potatoes were recorded. Blighted tubers were removed at the first assessment. At the end of the incubation period tubers were washed and a second tuber blight assessment was made. In the UK tubers were washed, and dried quickly under ventilation, prior to the first assessment. The data from both assessments were combined and the percentage tuber blight was calculated based on tuber weight and number separately. Statistical analysis All statistical analyses were done with Genstat 19th ed. (Payne et al., 2009). A mixed linear model analysis, using the restricted maximum likelihood estimates (REML) was used to analyse the StAUDPC data. REML analysis was used because not all fungicides were included in every experiment. A mixed model consists of fixed treatment terms (here fungicide) and random block terms (here experiment, block and plot; formula 1 (Montgomery and Peck, 1982 ): $$\:StAUDP{C}_{ijkp}=\mu\:+{E}_{i}+{B}_{ij}+{\beta\:}_{k}+{P}_{ijp}$$ 1 , Where: µ = overall mean E i = effect of experiment i ~ N (0, σ E 2 ) B ij = effect of block j within experiment i ~ N (0, σ B 2 ) P ijp = effect of plot p within block B ij ~ N (0, σ P 2 ) β k = effect of fungicide k StAUDPC was analysed instead of AUDPC because the assessment period was not equal in all trials. StAUDPC equals the AUDPC divided by the number of days between first and final disease assessments. Plots with high residuals were identified to establish non-consistent performance of fungicides. Replicates 1 and 2 of the 2006 experiment in the Netherlands were omitted from the analysis. Based on the average StAUDPC (mStAUDPC), ratings for the effectiveness of the fungicides to control foliar blight were calculated, according to formula (2), thus ratings varied between 2 (represented by mancozeb sprayed at 1500 g active ingredient /ha). $$\:\text{E}{\text{R}}_{k}=3\frac{\text{MAX}\left(y\right)-{y}_{k}}{\text{MAX}\left(y\right)}+2$$ 2 , ER k = efficacy rating of the fungicide k to control potato late blight during the whole growing season. y = mStAUDPC MAX (y) = mStAUDPC of the fungicide with the highest mStAUDPC determined in the series of experiments. Based on the average tuber blight (mStAUDPC), ratings for the effectiveness of the fungicides to control tuber blight were calculated, according to formula (3), thus ratings varied between 0 and 5 (0 represented by mancozeb sprayed at 1.5 kg active ingredient/ha used as a reference and is considered not effective to control tuber blight.). $$\:\text{E}{\text{R}}_{k}=5\frac{\text{MAX}\left(y\right)-{y}_{k}}{\text{MAX}\left(y\right)}$$ 3 , ER k = efficacy rating of the fungicide k to control tuber blight y = m_tuber_blight MAX (y) = m_tuber_blight of the fungicide with the highest tuber blight incidence determined in the series of experiments. Based on the average StAUDPC (mStAUDPC), ratings for the effectiveness of the fungicides to control early blight were calculated, according to formula (4) $$\:\text{E}{\text{R}}_{k}=5\frac{\text{MAX}\left(y\right)-{y}_{k}}{\text{MAX}\left(y\right)}$$ 4 , ER k = efficacy rating of the fungicide k to control early blight during the growing season. y = mStAUDPC MAX (y) = mStAUDPC of the untreated control as a reference fixed at 0.0 Late blight or early blight disease pressure varied with each experiment. The REML directive takes the specific conditions of the experiment into account. For example, if fungicides A and B were tested in different years and fungicide A was in experiments with a relatively high disease pressure, and fungicide B was exposed to a relatively low disease pressure, then the arrhythmic mean of mStAUDPC of fungicide A would be adjusted with a decrease and fungicide B would be adjusted with a rise of mStAUDPC. By doing so the disease pressure for all the fungicides is adjusted to the same level, making a fair comparison between fungicides in different experiments possible. Results The mean StAUDPC values for nine coded fungicides still registered in the EU in 2025 and the derived foliar blight efficacy ratings are shown in Table 1 . The reference treatment mancozeb was always rated as 2.0 on the 2.0 to 5.0 scale. Also included in the table are the ratings for the control of tuber blight for four fungicides still approved in the European Union. For tuber blight the reference treatment mancozeb was rated 0.0 on the 0.0 to 5.0 scale. Table 1 Coded fungicides tested to provide efficacy ratings for the control of foliar and tuber blight using a 7-day spray schedule. Foliar blight Tuber blight Fungicide code StAUDPC 1 Rating Fungicide code StAUDPC 1 %TBw 1 Rating mancozeb (1500 g/ha) 23.4 2.0 mancozeb (1500 g/ha) 14.3 4.9 0 EXP06-01 2 9.0 3.8 TXP09-01 2 8.4 1.1 3.9 EXP06-02 9.0 3.8 TXP09-02 11.9 1.2 3.8 EXP06-03 7.7 4.0 TXP09-03 8.4 0.4 4.6 EXP06-04 16.2 2.9 TXP19-01 4.5 1.5 3.9 EXP13-07 4.6 4.4 EXP14-06 7.7 4.0 EXP15-02 10.9 3.6 EXP17-01 0.1 4.9 EXP19-02 1.1 4.9 1 Mean of ≥ 6 trials 2 The first 2 digits gives the year of entering the EuroBlight trials, 06 means 2006. EXP06-01 (62.5 g/L fluopicolide + 625 g/L propamocarb hydrochloride) @ 1.6 L/ha; EXP06-02 (160 g/L cyazofamid) @ 0.5 L/ha, EXP06-03 (250 g/L mandipropamid) @ 0.6 L/ha, EXP06-04 (500 g/L fluazinam) @ 0.4 L/ha, EXP13-07, (250 g/l mandipropamid + cymoxanil) @ 0.6 L/ha, EXP14-06 ((330 g/kg zoxamide + 330 g/kg cymoxanil) + 500 g/l fluazinam) @ 0.45 L/ha + 0.4 L/ha, EXP15-02 (150 g/L azoxystrobin + 375 g/L fluazinam) @ 0.5 L/ha, EXP17-01 (100 g/L oxathiapiprolin + 200 g/L amisulbrom) @ 0.15 L/ha + 0.3 L/ha, EXP19-02 (48 g/ L oxathiapiprolin + 240 g/L amisulbrom) @ 0.25 l/ha. TXP09-01 (62.5 g/L fluopicolide + 625 g/L propamocarb hydrochloride) @ 1.6 L/ha, TXP09-02 (160 g/L cyazofamid) @ 0.5 L/ha, TXP09-03 (160 g/L cyazofamid) + (333.6 g/L propamocarb + 50g/L cymoxanil) @ 0.5 L/ha + 2.0 L/ha, TXP-19 (48 g/ L oxathiapiprolin + 240 g/L amisulbrom) @ 0.25 L/ha. The average StAUDPC values for early blight in plots sprayed with fungicides, either at 14- day or 7-day intervals, along with decimal ratings, are shown in Table 2 . Only the fungicides for which a rating was published in the EuroBlight table were included in the calculations. Table 2 StAUDPC values and corresponding fungicide efficacy ratings for treatments to control early blight in a 14- or 7-day spray schedule. Fungicide Code (14-day) StAUDPC 1 Rating Fungicide Code (7-day) StAUDPC 1 Rating A-15-14-01 2 2.1 4.5 A-15-7-01 2 6.1 3.5 A-15-14-02 7.1 3.3 A-15-7-04 8.3 3.0 A-15-14-04 7.0 3.3 A-15-7-06 5.7 3.6 A-15-7-07 4.6 3.9 A-18-14-01 2.8 4.3 A-15-7-08 6.0 3.5 mancozeb (2500 g a.i. / ha) 10.4 2.3 mancozeb (2500 g a.i. / ha) 7.1 3.2 UTC 19.9 0.0 UTC 19.9 0.0 1 Mean of ≥ 6 trials 2 The first 2 digits gives the year of entering the EuroBlight trials, 15 means 2015 A-15-14-01 (125 g/L fluopryram + 125 g/L prothioconazole) @ 0.5 L/ha; A-15-14-02 (250 g/L difenoconazole) @ 0.5 L/ha; A-15-1-404 (250 gl/L difenoconazole + 250 gl/L mandipropamid) @ 0.6 L/ha; A-18-14-01 Belanty (75 g/Lmefentriconazole) @ 1.25 L/ha A-15-7-01 (83 g/L zoxamide + 667 g/L mancozeb) @ 1.8 kg/ha; A-15-7-04 (75 g/L fenamidone + 375 g/L propamocarb) @ 2.0 L/ha ; A-15-7-06 (150 g/L azoxystrobin + 375 g/L fluazinam) @ 0.5 L/ha; A-15-7-08 (dimethomorph + mancozeb) @ 2.0 kg/ha. Discussion The aim of the experiments was to rate the efficacy of fungicides to control foliar blight, tuber blight and early blight using data generated from multi-year and multi-country field experiments with standard protocols instead of a consensus of expert judgement. The ratings could be used by growers, extension services and scientists to develop efficient control strategies based on the quantitative characteristics of the fungicides tested. During a EuroBlight meeting it was decided that a rating could only be awarded if the fungicide being tested was in a minimum of six successful experiments. Furthermore, the experiments should have been conducted in at least 3 different countries and for a minimum of 2 growing seasons. More than 6 experiments were allowed, however each additional valid experiment was to be included in the rating calculation. An experiment was considered not valid if the disease severity did not exceed the threshold of 10% disease severity in the worst treatment (most often the reference treatment). In the calculations for foliar and tuber blight ratings presented here, only fungicides registered in the EU were used. Although mancozeb is not registered in the EU anymore, this fungicide was almost always used as a reference; the exception was for the tuber blight experiment in the Netherlands in 2009. More fungicides, i.e. those that are still approved outside of the EU, are included in the database and have their ratings published on the EuroBlight website. For early blight all registered fungicides were used in the calculations. Fungicide resistance In the experiments fungicides were sprayed season long, or shorter during the relevant period in case of tuber blight and early blight. Spraying fungicides was usually not according to the label and not according to the FRAC guidelines pertaining to fungicide resistance management for P. infestans and A. solani . However, it was in accordance with EPPO guidelines for registration purposes. Repeated sprays with the same fungicide might select for fungicide resistance (Grünwald et al., 2006 ); this must be avoided for commercial crops because of their very large hectarage. In 2006 when the first foliar blight experiments took place only resistance to metalaxyl (Davidse et al., 1981 ) was known. During the next 20 years resistance or reduced sensitivity was also found for fluazinam (Schepers et al., 2018 ), mandipropamid (Abuley et al, 2023 ), and oxysterol binding protein fungicides (OSBP) (Anonymous, 2024a ) in the P. infestans population. For the A. solani population resistance has been described for two FRAC groups: quinone outside inhibitors (Gudmestad, et al., 2013 ; Leiminger et al.,2013) and succinate dehydrogenase inhibitors (Wharton et al., 2012 ; Landschoot et al., 2017 ). On the EuroBlight website it is stated that “Ratings can be lower where resistant isolates are present, depending on their frequency and the mechanism of resistance, leading to variable impact on product efficacy. Resistance management strategies should always be implemented as part of Integrated Disease Management, regardless of the absence or presence of resistance. Please refer to the FRAC website for the corresponding resistance management guidelines.” If fungicide resistance occurred within a ratings experiment, the data for any product containing the affected fungicide active(s) were considered invalid. This is because the aim was to rate potential efficacy. Foliar blight The reference treatment mancozeb is a multisite fungicide (coded M 03) (Anonymous, 2024b) and thus less prone to fungicide resistance development within the P. infestans population. Therefore, it was expected that the performance of mancozeb throughout the years would be stable and it was decided to make its rating a constant, 2.0. In the first EuroBlight tables a scale of - to +++ was used. For the quantitative ratings we opted for a similar range, 2.0 to 5.0. A rating of 5.0 represents no visible lesions on the foliage. Theoretically a rating lower than 2.0 would be possible, however during the years of the experiments such a rating has not been published in the EuroBlight table. It must be noted that a rating is only published after the fungicide meets the test requirements and there is agreement between the managers of the crop protection company and of the EuroBlight trials. Tuber blight No untreated control was included but it would have been an unsuitable reference because the foliar blight epidemic in untreated plots is fast, resulting in too short a period with a sufficiently sporulating canopy. For tubers to become infected the presence of large numbers of sporangia on the haulm and precipitation/irrigation is necessary. The more the epidemic is prolonged the more opportunity for tuber infection to occur. Several publications comment on there being low incidences of tuber blight after a strong foliar blight epidemic with early haulm death (Gray, 1958 ; Fehrmann, 1963 ; Hirst et al., 1965 ; Ullrich, 1967 ; Bochow et al., 1979 ). Therefore, in the tuber blight trials, mancozeb was chosen as the reference treatment. Based on expert judgment it was expected that mancozeb was not able to control tuber blight, thus by definition its rating should be a constant 0.0. The maximum rating was set at 5.0. This could only be achieved if no tuber blight was found in any of the minimum of 6 experiments in which the candidate fungicide was tested. The severity of 0.5% was considered the optimum severity of blight to start with the first application of the test candidate. Lower than this would most likely result in the tuber blight incidences being confounded by markedly different foliar epidemic curves for the candidates. Delaying the first application of the test fungicides until leaf blight was substantially greater than 0.5% risked an unwelcome, high background incidence of tuber blight in all treatments. Early blight In contrast to late blight, in the early blight rating experiments the untreated control was accepted as the reference treatment. Obviously, the untreated control shows no efficacy in controlling A. solani and therefore it is rated 0.0. There are fungicides specifically targeted at A. solani , which usually are sprayed at 14-day intervals. There are also fungicides aimed at P. infestans , but with a side effect on A. solani. These fungicides are normally sprayed every 7 days. In the EuroBlight table these two groups are listed separately. EuroBlight Table Fungicide ratings have been published from within a few years of the ratings trials starting. The table has been developed over many years, with new data added almost every year. However, ratings when published were fixed. In the UK five independent trials validated the accuracy of the EuroBlight ratings for the fungicides tested, especially if curative ratings were also taken into account (Bain et al., 2017 ). In conclusion, this study has described a systematic approach to rating the efficacy of fungicides. The data used in this study were generated over several growing seasons (2006–2023) and in four different countries (Denmark, the Netherlands, Germany, and the United Kingdom). The method stipulates that a fungicide can only be rated if there are results from successful replicated field experiments conducted over at least two growing seasons, using a susceptible variety, and in at least three different European countries. Additionally, spatially uniform disease pressure, achievable through the inclusion of spreader rows and the maintenance of a disease-conducive environment (e.g., by misting the field via sprinkler irrigation), is necessary to ensure a successful experiment. Importantly, the procedure allows ratings to be calculated even although candidate fungicides are tested in different years. Overall, the method developed and validated in this study is robust and provides an objective procedure for deriving numeric ratings for fungicides, not just for potato late blight and early blight, but also for other host-pathosystems. Statements and Declarations The authors declare no competing interests. Acknowledgements This research was funded by crop protection companies (Adama, Bayer CropScience, BASF, Belchim Crop Protection, Certis Europe BV, Certis Belchim, Corteva, Dow AgroSciences, FMC, Gowan, Indofil Industries LTD, Isagro Ricera S.r.l., ISK, Nissan Chemical Europe SAS, Nufarm, Oxon, Syngenta, UPL) who submitted fungicides to be rated and included in the EuroBlight fungicide table. The authors would also like to thank Nick Bradshaw and Bent Jørgen Nielsen for their contribution to the protocols and the set-up of the initial experiments. The authors would like to thank the late Wim van den Berg for helping to put the necessary statistical procedures in place. References Abuley, IK, Hansen, JG (2021). An epidemiological analysis of the dilemma of plant age and late blight ( Phytophthora infestans ) susceptibility in potatoes. Eur J Plant Pathol 161, 645–663. https://doi.org/10.1007/s10658-021-02350-4 Abuley IK, Lynott JS, Hansen JG, Cooke DEL, Lees AK. (2023). The EU43 genotype of Phytophthora infestans displays resistance to mandipropamid. Plant Pathology 72 (7): 1305-1313 https://doi.org/10.1111/ppa.13737 Anonymous (2020). Efficacy evaluation of fungicides. PP 1/002(5) Phytophthora infestans on potato. Bulletin OEPP/EPPO Bulletin (2020) 0 (0), 1–4. DOI: 10.1111/epp.12708 Anonymous (2008). Efficacy evaluation of fungicides. PP1/263 (1) Alternaria solani and Alternaria alternata on potato and outdoor production of tomato. European and Mediterranean Plant Protection Organization. Anonymous (2024a). Minutes of the FRAC OSBPI Working Group Meeting 7 February 2024. OSBPI Working Group FRAC. Anonymous (2024a). FRAC Code List©* 2024: Fungal control agents sorted by cross-resistance pattern and mode of action. Bain RA, Schepers H, Nielsen B, Bradshaw N (2009). Protocol for testing “Effectiveness: tuber blight” ( Phytophthora infestans ). Bain RA, Kenndy C, Kiltie D (2017). Foliar late blight development in the UK in relation to EuroBlight fungicide efficacy ratings. PAGV – SPECIAL REPORT NO 18 – 2017, 269-272. Bochow H, Krochert R, Tarnow W. (1979) Hinweise auf einige das Auftreten und die Bekämpfung der Kartoffelbraunfäule (Phytophthora infestans) betreffende Zusammenhänge. Nachrichtenblatt Pflanzenschutzdienst DDR 24, 225-229. Campbell CL, Madden LV (1990). Introduction to Plant Disease Epidemiology. John Wiley & Sons, New York. 532 p. Cooke LR, Schepers HTAM, Hermansen A, Bain RA, Bradshaw NJ, Ritchie F, Shaw DS, Evenhuis A, Kessel, GJT, Wander JGN, Andersson B, Hansen JG, Hannukkala A, Nærstad R, Nielsen BJ (2011). Epidemiology and integrated control of potato late blight in Europe. Potato Research 54 , 183-222. https://doi.org/10.1007/s11540-011-9187-0 Davidse LC, Looijen D, Turkensteen LJ, Van der Wal D. (1981). Occurrence of metalaxyl-resistant strains of Phytophthora infestans in Dutch potato fields. Netherlands Journal of Plant Pathology 87, 65–68. https://doi.org/10.1007/BF01976658 Evenhuis B, Leiminger J, Nielsen B, Hausladen H, Spoelder J, Kapsa, J, Vanhaverbeke P, Shtienberg, D, Schepers H (2019) Protocol for testing effectiveness to control early blight. EuroBlight meeting York Ellis MB, Gibson IAS (1975). Alternaria solani. Descriptions of fungi and bacteria 48, sheet 475. https://doi.org/10.1079/DFB/200564004 Fehrmann, H. (1963) Untersuchungen zur Pathogenese der durch Phytophthora infestans hervorgerufenen Braunfäule der Kartoffelknolle. Phytopath. Z. 46, 371-408 Gray, E.G. (1958): The control of blight in potato crops. Scottish Agric. 38, 46-47. Grünwald NJ, Sturbaum AK, Montes GR, Serrano EG, Lozoya-Saldaña H, Fry WE (2006). Selection for fungicide resistance within a growing season in field populations of Phytophthora infestans in the center of origin. Phytopathology 96 , 1397-1403. Gudmestad NCS, Arabiat S, Pasche JS, Miller, JS (2013). Prevalence and impact of SDHI fungicide resistance in Alternaria solani . Plant Dis. 97:952-960. Leiminger JH, Adolf B, Hausladen H (2013) Occurrence of the F129L mutation in Alternaria solani populations in Germany in response to QoI application, and its effect on sensitivity. First published: 29 July 2013 https://doi.org/10.1111/ppa.12120Cit Haverkort AJ, Boonekamp PM, Hutten R, Jacobsen E, Lotz LAP, Kessel GJT, Visser RGF, van der Vossen EAG (2008) Societal costs of late blight in potato and prospects of durable resistance through cisgenic modification. Potato Res 51:47–57. Hirst, JM, Stedman OJ, Lacey J, Hide GA (1965) The epidemiology of Phytophthora infestans . IV. Spraying trails, 1959 to 1963, and the infection of tubers. Ann. appl. Biol. 55, 373-395. Montgomery DC, Peck EA. (1982). Introduction to Linear Regression Analysis. John Wiley & Sons. New York. Landschoot S, Carrette J, Vandecasteele M, De Baets B, Hofte M, Audenaert K, Haesaert G (2017). Boscalid-resistance in Alternaria alternata and Alternaria solani populations: An emerging problem in Europe. Crop Protection 92 (2017) 49-59. Payne RW. (2009). GenStat. WIREs Computational Statistics Volume 1, Issue 2, Sep 2009: 131-260. https://doi.org/10.1002/wics.32 Schepers HTAM, Evenhuis A, Spits, H. G. (2009). Strategies to control late blight in potatoes in Europe. Acta Horticulturae, (834), 79–82. Schepers HTAM, Kessel GJT, Lucca F, Förch MG, Van den Bosch GBM, Topper CG, Evenhuis A. (2018). Reduced sensitivity of fluazinam against Phytophthora infestans in the Netherlands. European Journal of Plant Pathology 151 , 947-960. Schepers H, Nielsen B, Bradshaw N, Bain RA (2007). Effectiveness of fungicides against foliage blight caused by Phytophthora infestans . Euroblight Protocol – Version 1.0 – 30 October 2007. https://agro.au.dk/fileadmin/Effectiveness_leaf_late_blight.pdf Ullrich J. (1967) Die Braunfäule der Kartoffel (Phytophthora infestans [Mont.] de Bary). Nachrichtenblatt Deut. Pflanzenschutzd. (Braunschweig) 19, 55-59. Wharton P, Fairchild K, Belcher A, Wood E, (2012). First report of in vitro boscalid resistant isolates of Alternaria solani causing early blight of potato in Idaho. Plant Dis. 96, 454. Supplementary Files TableS1RB.docx Cite Share Download PDF Status: Published Journal Publication published 13 Mar, 2026 Read the published version in Potato Research → Version 1 posted Editorial decision: Minor revisions 14 Oct, 2025 Reviewers agreed at journal 09 May, 2025 Reviewers invited by journal 08 May, 2025 Editor invited by journal 25 Apr, 2025 Editor assigned by journal 25 Apr, 2025 First submitted to journal 23 Apr, 2025 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-6305294","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":453710961,"identity":"8acd43c7-3a99-4822-94b3-7caa47322fe3","order_by":0,"name":"A Evenhuis","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA4klEQVRIiWNgGAWjYBACexDB+AdISDAwHGCoAAsyHsCnxbCBgbGBsQGm5QxEFK8WgwNIWhgY24jQYtje+/wBY8NhOXPpHsODP+cdTtzewHsArxZ7nuOGDYw/DhtbzjljcJh32+HEOQf4EvDbMiMN5LC0xA03cgwOM267nTiDgccAv1/uPwNrqQdpOfhzDjFabrCBtNgkGAC1HOBtIEKLYU8a44zEBhvDDTfSCg7zHPtvPIOZgBZ79mMMHz7+kZA3uJG8+eOPmjTZGew9hg/waQGDBBQeM0H1o2AUjIJRMAoIAQC5M1OupVjjcAAAAABJRU5ErkJggg==","orcid":"https://orcid.org/0000-0002-6895-1190","institution":"Wageningen University and Research Wageningen Plant Research","correspondingAuthor":true,"prefix":"","firstName":"A","middleName":"","lastName":"Evenhuis","suffix":""},{"id":453710962,"identity":"41de0bb3-8770-4ad2-b813-4f358dab90af","order_by":1,"name":"A. Evenhuis","email":"","orcid":"","institution":"Wageningen University and Research Wageningen Plant Research","correspondingAuthor":false,"prefix":"","firstName":"A.","middleName":"","lastName":"Evenhuis","suffix":""},{"id":453710963,"identity":"276ece7a-de01-467a-bf2f-c8825f74fab5","order_by":2,"name":"R.A. Bain","email":"","orcid":"","institution":"SRUC: Scotland's Rural College","correspondingAuthor":false,"prefix":"","firstName":"R.A.","middleName":"","lastName":"Bain","suffix":""},{"id":453710964,"identity":"cef30d76-d864-440d-a58c-6afcf18d3038","order_by":3,"name":"I.K. Abuley","email":"","orcid":"","institution":"Aarhus University: Aarhus Universitet","correspondingAuthor":false,"prefix":"","firstName":"I.K.","middleName":"","lastName":"Abuley","suffix":""},{"id":453710965,"identity":"a9a60e8f-0eb8-4cd5-a393-1e819b5ab41e","order_by":4,"name":"H. Hausladen","email":"","orcid":"","institution":"Technische Universität München: Technische Universitat Munchen","correspondingAuthor":false,"prefix":"","firstName":"H.","middleName":"","lastName":"Hausladen","suffix":""},{"id":453710966,"identity":"83b626be-b2f1-4c57-a896-dc97007b7bb1","order_by":5,"name":"H.T.A.M. Schepers","email":"","orcid":"","institution":"-","correspondingAuthor":false,"prefix":"","firstName":"H.T.A.M.","middleName":"","lastName":"Schepers","suffix":""}],"badges":[],"createdAt":"2025-03-25 15:38:08","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6305294/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6305294/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1007/s11540-026-10014-1","type":"published","date":"2026-03-13T15:57:51+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":104739310,"identity":"64eb6408-76fd-444e-95a3-fd1da46c0744","added_by":"auto","created_at":"2026-03-16 16:01:31","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":647442,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6305294/v1/79af888b-436c-4874-a329-8aab7651aa83.pdf"},{"id":82584912,"identity":"7c0bb783-95d0-4360-846e-4133419d6253","added_by":"auto","created_at":"2025-05-13 06:59:29","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":20221,"visible":true,"origin":"","legend":"","description":"","filename":"TableS1RB.docx","url":"https://assets-eu.researchsquare.com/files/rs-6305294/v1/c801e1341fdd4fc05d4601bf.docx"}],"financialInterests":"","formattedTitle":"Methodology to determine fungicide efficacy ratings for the EuroBlight tables – potato late or early blight","fulltext":[{"header":"Introduction","content":"\u003cp\u003eThe oomycete \u003cem\u003ePhytophthora infestans\u003c/em\u003e is the causal organism of potato late blight, the most important disease in potato cultivation in northwestern Europe with its maritime climate (Haverkort et al., \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2008\u003c/span\u003e). Early blight, caused by \u003cem\u003eAlternaria solani\u003c/em\u003e, is more important in eastern and south Europe, where the weather is characterized as a continental climate, although the pathogen is found ranging from tropical conditions to a temperate climate (Ellis \u0026amp; Gibson, \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e1975\u003c/span\u003e). Fungicides play a crucial role in the integrated control of both late blight and early blight. Typically, fungicides are sprayed on a weekly basis to control these diseases, given the explosive nature of both. As an example, in the Netherlands the average number of sprays to control potato late blight per season varies from 7 to 20 depending on the weather, disease pressure and resistance level of the potato variety (Schepers et al. \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2009\u003c/span\u003e; Cooke et al. \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2011\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eWhilst early blight is primarily a foliage disease, late blight attacks every part of the plant (e.g. leaves, stems, tubers). Therefore, it is important to use fungicides that effectively protect the leaves (early blight and late blight) as well as other plant parts such as tubers and stems (in the case of late blight). Each active ingredient has its own efficacies and specific characteristics, which are expressed in fungicide products. A EuroBlight fungicide table was set up to provide an overview of the relative ratings for each characteristic for different fungicides used to control late blight or and early blight. Until 2007 the EuroBlight ratings of the fungicides were based upon the judgement of experts from crop protection companies and independent researchers. However, this method was subjective and not based on standardized methodology. Accordingly, there was as a need to develop a more robust and objective method to evaluate the fungicides. Towards this aim, harmonised protocols were discussed among EuroBlight members, and it was proposed that the ratings of fungicides to control potato late blight (foliar and tuber blight) and early blight for the EuroBlight table were to be calculated based on results from field experiments carried out over 2 years and in at least 3 European countries. The objectives of this paper were to describe the method developed for rating the fungicides used for controlling late blight and early blight and to demonstrate its usefulness.\u003c/p\u003e"},{"header":"Materials and methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eGeneral aspect of the experiments\u003c/h2\u003e \u003cp\u003eField experiments were carried out to rate fungicides for controlling late blight on leaves (foliar blight) and tubers (tuber blight), and early blight. The experiments were conducted in Denmark, Germany, the Netherlands and United Kingdom. Foliar blight experiments were carried out in eighteen consecutive years (2006 to 2023). However, in some years tuber blight or early blight experiments were not requested (Table S1). For the foliar blight and tuber blight ratings in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e, only the fungicides registered in the EU in 2025 were used for the calculations. For early blight a limited number of fungicides was tested, and all were used for the calculations.\u003c/p\u003e \u003cp\u003eIn general, the trials conformed to local good agricultural practice. The exception was that many consecutive fungicide sprayings of the same product \u003cem\u003ewere\u003c/em\u003e carried out in a weekly scheme for late blight and in a weekly or fortnight scheme for early blight. The experiments were carried out in accordance with GEP. The cultivars planted were either susceptible to \u003cem\u003eP. infestans\u003c/em\u003e or \u003cem\u003eA. solani\u003c/em\u003e and were popular in the country in which the experiment was carried out. Plot size varied, depending on the experiment, but with a minimum of four rows. The minimum net plot consisted of 2 rows with a length of 8 m based on the EPPO protocols for late blight (Anonymous, \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2020\u003c/span\u003e) and early blight (Anonymous, \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2008\u003c/span\u003e). All experiments were arranged as randomized complete block designs with four, or sometimes five, replicates. In the late blight experiments, no untreated plots were included in the trial to avoid uneven disease pressure. To promote uniform disease pressure, untreated spreader rows of a susceptible variety were planted alongside the plots. The initial protocol for foliar blight is published on the EuroBlight website (Schepers et al., \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2007\u003c/span\u003e) There is also a protocol for tuber blight experiments (Bain et al., \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2009\u003c/span\u003e). In the Netherlands potato late blight trials were surrounded by a maize barrier since it this is required by law. In the early blight trials untreated plots were part of the experiment and were randomly allotted. Details are described in the Alternaria protocol (Evenhuis et al., \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2019\u003c/span\u003e).\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eFungicide applications\u003c/h3\u003e\n\u003cp\u003eTo be able to compare results obtained in different locations and years, reference treatments were included in the trials. In the foliar blight and tuber blight trials the reference treatment was mancozeb sprayed at 1500 g a.i./ha. In the early blight trial, the reference treatment was the untreated control.\u003c/p\u003e \u003cp\u003eFungicide applications were carried out by tractor-mounted or tractor-pulled sprayers. Spray volume varied from 200 to 400 l/ha and a pressure of 3 bar, depending on the trial location. In the foliar blight experiment spray applications were carried out with an interval of 7 days\u0026thinsp;\u0026plusmn;\u0026thinsp;1, depending on the weather conditions. The first application was done before the first infection so that the treatments were initially preventative. For the tuber blight experiments, in the rapid canopy phase cover sprays were applied. The choice of fungicide was left to the trial manager, but not one with high efficacy in controlling tuber blight. Until mancozeb was banned in the EU, usually this active ingredient was used, sometimes together with cymoxanil. The objective of the tuber blight control experiments was to compare the efficacy of fungicides in minimising the incidence of tuber blight through a direct effect, i.e. \u0026lsquo;activity against tuber infection as a result of fungicide application after infection of the haulm, during mid- to late-season when there is a direct effect on the tuber infection process\u0026rsquo;. Starting the test fungicides when the foliar blight severity reached approximately 0.5%, the candidates were sprayed at intervals of 7 days, with permitted variation of \u0026plusmn;\u0026thinsp;1 day depending on the weather conditions. For the early blight experiments, fungicide applications were carried out with 7- or 14-day intervals. The fungicides to be tested were sprayed multiple times consecutively, overriding label stipulations to avoid this for fungicide resistance management. For early blight and tuber blight, the first fungicide application was usually 6\u0026ndash;8 weeks after emergence. Fungicides were sprayed at the highest dose rate registered in Europe. When fungicides were not yet registered the expected highest dose rate was sprayed. In the early blight trials late blight was managed by using fungicides that had no efficacy against A. solani.\u003c/p\u003e\n\u003ch3\u003eInoculation\u003c/h3\u003e\n\u003cp\u003eThe details below are a summary of the methodologies used in the four countries. It should be noted that there was minor variation in some details between sites. In the foliar and tuber blight trials, spreader rows were planted alongside the fungicide plots. These spreader rows were not sprayed against potato late blight. Next to each plot one potato plant in the spreader row was inoculated with \u003cem\u003eP. infestans.\u003c/em\u003e The \u003cem\u003eP. infestans\u003c/em\u003e genotypes used depended on the year and location of the experiment. Genotypes frequently used in all countries were EU-13-A2 and EU-36-A2; sometimes 6_A1 (UK only). For some trials inoculum was prepared as described in Abuley and Hansen (\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2021\u003c/span\u003e): (1) mycelial plugs of the \u003cem\u003eP. infestans\u003c/em\u003e isolates were transferred to rye B agar media and incubated under fluorescent light at 17\u0026thinsp;\u0026plusmn;\u0026thinsp;2\u0026deg;C (Denmark) or 15\u0026deg;C elsewhere; (2) detached leaves of the late blight-susceptible cultivar Bintje were inoculated with a sporangial suspension from step one. Sporangia formed on the leaves were harvested and adjusted to 10000 sporangia/ml for inoculating the spreader-row plants. Inoculation was sometimes performed in the evening when relative humidity was high, spraying approximately 10 ml of inoculum per potato plant. Extended leaf wetness was achieved by irrigating the entire field before inoculation. If weather conditions were unsuitable, inoculation was postponed until the next day, or inoculated plants were sealed in polythene bags, which were removed early the next morning. For some trials there was also natural infection at some point during the growing season. In later trials the genotype composition of the \u003cem\u003eP. infestans\u003c/em\u003e population in the trial field was recorded.\u003c/p\u003e \u003cp\u003eInoculation of the \u003cem\u003eAlternaria solani\u003c/em\u003e experiments was optional. In Germany infection usually relied on natural inoculum sources. In Denmark and the Netherlands trials were inoculated by broadcasting barley (Denmark) or wheat (the Netherlands) kernels, that had been infected by \u003cem\u003eA. solani\u003c/em\u003e, between the potato ridges thus increasing the disease pressure. Subsequent infection of the trial relied on natural weather conditions.\u003c/p\u003e\n\u003ch3\u003eSprinkler irrigation\u003c/h3\u003e\n\u003cp\u003eTo enhance the development of late blight when conditions were not favourable, sprinkler irrigation was applied. In the Netherlands sprinkler irrigation was carried out from 22:00 to 02:30 and from 05:00 to 08:30. Each hour the sprinklers ran for 1 minute. For some tuber blight experiments irrigation was applied to the blighted trial. This was normally 1 day after fungicide application. The water volume applied varied from 10 to 20 mm. Irrigation was omitted when natural precipitation was sufficient to transfer spores from the haulm to the progeny tubers.\u003c/p\u003e\n\u003ch3\u003eDisease assessment\u003c/h3\u003e\n\u003cp\u003eDuring the growing season potato late blight severity (percentage foliage destroyed by \u003cem\u003eP. infestans\u003c/em\u003e) was assessed visually at weekly intervals, both in the foliar blight and tuber blight experiments. The last assessment had to be within 7 days of the final application of fungicide for that data to be included in the calculation of a rating. In the early blight trials disease severity was visually assessed weekly from the onset of first symptoms in the untreated control until the crop was completely senescent. A trial was considered successful if the disease severity of the worst treatment, including the reference, was \u0026ge;\u0026thinsp;10%. To facilitate statistical analysis, the standardized area under the disease progress curve (StAUDPC) was calculated for both late blight and early blight (Campbell and Madden \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e1990\u003c/span\u003e). The StAUDPC is a standardized version of the area under the disease progress curve (AUDPC), which allows comparisons of epidemics of varying duration.\u003c/p\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003eHarvesting of tubers and tuber blight assessment\u003c/h2\u003e \u003cp\u003eAt the end of the growing season the haulm (leaves plus stems) of the tuber blight trials was killed using a herbicide desiccant. Harvest of the tubers did not take place until all of the leaves and stems had been completely dead for at least 2 weeks. Progeny tubers were harvested from the middle two rows. Tuber samples (35\u0026ndash;50 kg / plot) were taken for each treatment for subsequent assessment. The target number of tubers to be assessed per treatment was 1600. To reduce the risk of tuber infection during harvest further, tubers were dried quickly under ventilation from the day of harvest. Tuber blight assessments were made shortly after harvest and again after incubation in a non-refrigerated store for about 3 weeks to 3 months. Both number and weight of the blight-free and blighted potatoes were recorded. Blighted tubers were removed at the first assessment. At the end of the incubation period tubers were washed and a second tuber blight assessment was made. In the UK tubers were washed, and dried quickly under ventilation, prior to the first assessment. The data from both assessments were combined and the percentage tuber blight was calculated based on tuber weight and number separately.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003eStatistical analysis\u003c/h2\u003e \u003cp\u003eAll statistical analyses were done with Genstat 19th ed. (Payne et al., 2009). A mixed linear model analysis, using the restricted maximum likelihood estimates (REML) was used to analyse the StAUDPC data. REML analysis was used because not all fungicides were included in every experiment. A mixed model consists of fixed treatment terms (here fungicide) and random block terms (here experiment, block and plot; formula 1 (Montgomery and Peck, \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e1982\u003c/span\u003e):\u003cdiv id=\"Equ1\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ1\" name=\"EquationSource\"\u003e\n$$\\:StAUDP{C}_{ijkp}=\\mu\\:+{E}_{i}+{B}_{ij}+{\\beta\\:}_{k}+{P}_{ijp}$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e1\u003c/div\u003e\u003c/div\u003e,\u003c/p\u003e \u003cp\u003eWhere:\u003c/p\u003e \u003cp\u003e\u0026micro;\u0026thinsp;=\u0026thinsp;overall mean\u003c/p\u003e \u003cp\u003e \u003cem\u003eE\u003c/em\u003e \u003csub\u003e \u003cem\u003ei\u003c/em\u003e \u003c/sub\u003e = effect of experiment \u003cem\u003ei\u003c/em\u003e\u0026thinsp;~\u0026thinsp;\u003cem\u003eN\u003c/em\u003e(0, σ\u003csub\u003e\u003cem\u003eE\u003c/em\u003e\u003c/sub\u003e\u003csup\u003e2\u003c/sup\u003e)\u003c/p\u003e \u003cp\u003e \u003cem\u003eB\u003c/em\u003e \u003csub\u003e \u003cem\u003eij\u003c/em\u003e \u003c/sub\u003e = effect of block \u003cem\u003ej\u003c/em\u003e within experiment \u003cem\u003ei\u003c/em\u003e\u0026thinsp;~\u0026thinsp;\u003cem\u003eN\u003c/em\u003e(0, σ\u003csub\u003e\u003cem\u003eB\u003c/em\u003e\u003c/sub\u003e\u003csup\u003e2\u003c/sup\u003e)\u003c/p\u003e \u003cp\u003e \u003cem\u003eP\u003c/em\u003e \u003csub\u003e \u003cem\u003eijp\u003c/em\u003e \u003c/sub\u003e = effect of plot \u003cem\u003ep\u003c/em\u003e within block \u003cem\u003eB\u003c/em\u003e\u003csub\u003e\u003cem\u003eij\u003c/em\u003e\u003c/sub\u003e ~\u003cem\u003eN\u003c/em\u003e(0, σ\u003csub\u003e\u003cem\u003eP\u003c/em\u003e\u003c/sub\u003e\u003csup\u003e2\u003c/sup\u003e)\u003c/p\u003e \u003cp\u003eβ\u003csub\u003ek\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;effect of fungicide \u003cem\u003ek\u003c/em\u003e\u003c/p\u003e \u003cp\u003eStAUDPC was analysed instead of AUDPC because the assessment period was not equal in all trials. StAUDPC equals the AUDPC divided by the number of days between first and final disease assessments.\u003c/p\u003e \u003cp\u003ePlots with high residuals were identified to establish non-consistent performance of fungicides. Replicates 1 and 2 of the 2006 experiment in the Netherlands were omitted from the analysis.\u003c/p\u003e \u003cp\u003eBased on the average StAUDPC (mStAUDPC), ratings for the effectiveness of the fungicides to control foliar blight were calculated, according to formula (2), thus ratings varied between 2 (represented by mancozeb sprayed at 1500 g active ingredient /ha).\u003cdiv id=\"Equ2\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ2\" name=\"EquationSource\"\u003e\n$$\\:\\text{E}{\\text{R}}_{k}=3\\frac{\\text{MAX}\\left(y\\right)-{y}_{k}}{\\text{MAX}\\left(y\\right)}+2$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e2\u003c/div\u003e\u003c/div\u003e,\u003c/p\u003e \u003cp\u003eER\u003csub\u003e\u003cem\u003ek\u003c/em\u003e\u003c/sub\u003e = efficacy rating of the fungicide \u003cem\u003ek\u003c/em\u003e to control potato late blight during the whole growing season.\u003c/p\u003e \u003cp\u003ey\u0026thinsp;=\u0026thinsp;mStAUDPC\u003c/p\u003e \u003cp\u003eMAX (y)\u0026thinsp;=\u0026thinsp;mStAUDPC of the fungicide with the highest mStAUDPC determined in the series of experiments.\u003c/p\u003e \u003cp\u003eBased on the average tuber blight (mStAUDPC), ratings for the effectiveness of the fungicides to control tuber blight were calculated, according to formula (3), thus ratings varied between 0 and 5 (0 represented by mancozeb sprayed at 1.5 kg active ingredient/ha used as a reference and is considered not effective to control tuber blight.).\u003cdiv id=\"Equ3\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ3\" name=\"EquationSource\"\u003e\n$$\\:\\text{E}{\\text{R}}_{k}=5\\frac{\\text{MAX}\\left(y\\right)-{y}_{k}}{\\text{MAX}\\left(y\\right)}$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e3\u003c/div\u003e\u003c/div\u003e,\u003c/p\u003e \u003cp\u003eER\u003csub\u003e\u003cem\u003ek\u003c/em\u003e\u003c/sub\u003e = efficacy rating of the fungicide \u003cem\u003ek\u003c/em\u003e to control tuber blight\u003c/p\u003e \u003cp\u003ey\u0026thinsp;=\u0026thinsp;m_tuber_blight\u003c/p\u003e \u003cp\u003eMAX (y)\u0026thinsp;=\u0026thinsp;m_tuber_blight of the fungicide with the highest tuber blight incidence determined in the series of experiments.\u003c/p\u003e \u003cp\u003eBased on the average StAUDPC (mStAUDPC), ratings for the effectiveness of the fungicides to control early blight were calculated, according to formula (4)\u003cdiv id=\"Equ4\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ4\" name=\"EquationSource\"\u003e\n$$\\:\\text{E}{\\text{R}}_{k}=5\\frac{\\text{MAX}\\left(y\\right)-{y}_{k}}{\\text{MAX}\\left(y\\right)}$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e4\u003c/div\u003e\u003c/div\u003e,\u003c/p\u003e \u003cp\u003eER\u003csub\u003ek\u003c/sub\u003e = efficacy rating of the fungicide k to control early blight during the growing season.\u003c/p\u003e \u003cp\u003ey\u0026thinsp;=\u0026thinsp;mStAUDPC\u003c/p\u003e \u003cp\u003eMAX (y)\u0026thinsp;=\u0026thinsp;mStAUDPC of the untreated control as a reference fixed at 0.0\u003c/p\u003e \u003cp\u003eLate blight or early blight disease pressure varied with each experiment. The REML directive takes the specific conditions of the experiment into account. For example, if fungicides A and B were tested in different years and fungicide A was in experiments with a relatively high disease pressure, and fungicide B was exposed to a relatively low disease pressure, then the arrhythmic mean of mStAUDPC of fungicide A would be adjusted with a decrease and fungicide B would be adjusted with a rise of mStAUDPC. By doing so the disease pressure for all the fungicides is adjusted to the same level, making a fair comparison between fungicides in different experiments possible.\u003c/p\u003e \u003c/div\u003e"},{"header":"Results","content":"\u003cp\u003eThe mean StAUDPC values for nine coded fungicides still registered in the EU in 2025 and the derived foliar blight efficacy ratings are shown in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. The reference treatment mancozeb was always rated as 2.0 on the 2.0 to 5.0 scale. Also included in the table are the ratings for the control of tuber blight for four fungicides still approved in the European Union. For tuber blight the reference treatment mancozeb was rated 0.0 on the 0.0 to 5.0 scale.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eCoded fungicides tested to provide efficacy ratings for the control of foliar and tuber blight using a 7-day spray schedule.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"9\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colspan=\"4\" nameend=\"c4\" namest=\"c1\"\u003e \u003cp\u003eFoliar blight\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"5\" nameend=\"c9\" namest=\"c5\"\u003e \u003cp\u003eTuber blight\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eFungicide code\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eStAUDPC\u003csup\u003e1\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eRating\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e \u003cp\u003eFungicide code\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eStAUDPC\u003csup\u003e1\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e%TBw\u003csup\u003e1\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003eRating\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"1\" nameend=\"c9\" namest=\"c9\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003emancozeb (1500 g/ha)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e23.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e \u003cp\u003emancozeb\u003c/p\u003e \u003cp\u003e(1500 g/ha)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e14.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e4.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"1\" nameend=\"c9\" namest=\"c9\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eEXP06-01\u003csup\u003e2\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e9.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e \u003cp\u003eTXP09-01\u003csup\u003e2\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e8.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e1.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e3.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"1\" nameend=\"c9\" namest=\"c9\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eEXP06-02\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e9.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e \u003cp\u003eTXP09-02\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e11.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e1.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e3.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"1\" nameend=\"c9\" namest=\"c9\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eEXP06-03\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e7.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e4.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e \u003cp\u003eTXP09-03\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e8.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e4.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"1\" nameend=\"c9\" namest=\"c9\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eEXP06-04\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e16.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e \u003cp\u003eTXP19-01\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e4.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e1.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e3.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"1\" nameend=\"c9\" namest=\"c9\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eEXP13-07\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e4.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e4.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colspan=\"1\" nameend=\"c9\" namest=\"c9\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eEXP14-06\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e7.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e4.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colspan=\"1\" nameend=\"c9\" namest=\"c9\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eEXP15-02\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e10.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colspan=\"1\" nameend=\"c9\" namest=\"c9\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eEXP17-01\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e4.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colspan=\"1\" nameend=\"c9\" namest=\"c9\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eEXP19-02\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e4.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colspan=\"1\" nameend=\"c9\" namest=\"c9\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"9\"\u003e\u003csup\u003e1\u003c/sup\u003e Mean of \u0026ge;\u0026thinsp;6 trials\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003csup\u003e2\u003c/sup\u003e The first 2 digits gives the year of entering the EuroBlight trials, 06 means 2006.\u003c/p\u003e \u003cp\u003eEXP06-01 (62.5 g/L fluopicolide\u0026thinsp;+\u0026thinsp;625 g/L propamocarb hydrochloride) @ 1.6 L/ha; EXP06-02 (160 g/L cyazofamid) @ 0.5 L/ha, EXP06-03 (250 g/L mandipropamid) @ 0.6 L/ha, EXP06-04 (500 g/L fluazinam) @ 0.4 L/ha, EXP13-07, (250 g/l mandipropamid\u0026thinsp;+\u0026thinsp;cymoxanil) @ 0.6 L/ha, EXP14-06 ((330 g/kg zoxamide\u0026thinsp;+\u0026thinsp;330 g/kg cymoxanil)\u0026thinsp;+\u0026thinsp;500 g/l fluazinam) @ 0.45 L/ha\u0026thinsp;+\u0026thinsp;0.4 L/ha, EXP15-02 (150 g/L azoxystrobin\u0026thinsp;+\u0026thinsp;375 g/L fluazinam) @ 0.5 L/ha, EXP17-01 (100 g/L oxathiapiprolin\u0026thinsp;+\u0026thinsp;200 g/L amisulbrom) @ 0.15 L/ha\u0026thinsp;+\u0026thinsp;0.3 L/ha, EXP19-02 (48 g/ L oxathiapiprolin\u0026thinsp;+\u0026thinsp;240 g/L amisulbrom) @ 0.25 l/ha.\u003c/p\u003e \u003cp\u003eTXP09-01 (62.5 g/L fluopicolide\u0026thinsp;+\u0026thinsp;625 g/L propamocarb hydrochloride) @ 1.6 L/ha, TXP09-02 (160 g/L cyazofamid) @ 0.5 L/ha, TXP09-03 (160 g/L cyazofamid) + (333.6 g/L propamocarb\u0026thinsp;+\u0026thinsp;50g/L cymoxanil) @ 0.5 L/ha\u0026thinsp;+\u0026thinsp;2.0 L/ha, TXP-19 (48 g/ L oxathiapiprolin\u0026thinsp;+\u0026thinsp;240 g/L amisulbrom) @ 0.25 L/ha.\u003c/p\u003e \u003cp\u003eThe average StAUDPC values for early blight in plots sprayed with fungicides, either at 14- day or 7-day intervals, along with decimal ratings, are shown in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. Only the fungicides for which a rating was published in the EuroBlight table were included in the calculations.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eStAUDPC values and corresponding fungicide efficacy ratings for treatments to control early blight in a 14- or 7-day spray schedule.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"7\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eFungicide\u003c/p\u003e \u003cp\u003eCode (14-day)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eStAUDPC\u003csup\u003e1\u003c/sup\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eRating\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eFungicide\u003c/p\u003e \u003cp\u003eCode (7-day)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eStAUDPC\u003csup\u003e1\u003c/sup\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003eRating\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eA-15-14-01\u003csup\u003e2\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e4.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eA-15-7-01\u003csup\u003e2\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e6.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e3.5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eA-15-14-02\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e7.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eA-15-7-04\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e8.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e3.0\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eA-15-14-04\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e7.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eA-15-7-06\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e5.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e3.6\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eA-15-7-07\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e4.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e3.9\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eA-18-14-01\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e4.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eA-15-7-08\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e6.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e3.5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003emancozeb\u003c/p\u003e \u003cp\u003e(2500 g a.i. / ha)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e10.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003emancozeb\u003c/p\u003e \u003cp\u003e(2500 g a.i. / ha)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e7.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e3.2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eUTC\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e19.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eUTC\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e19.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0.0\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"7\"\u003e\u003csup\u003e1\u003c/sup\u003e Mean of \u0026ge;\u0026thinsp;6 trials\u003c/td\u003e\u003c/tr\u003e \u003ctr\u003e\u003ctd colspan=\"7\"\u003e\u003csup\u003e2\u003c/sup\u003e The first 2 digits gives the year of entering the EuroBlight trials, 15 means 2015\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eA-15-14-01 (125 g/L fluopryram\u0026thinsp;+\u0026thinsp;125 g/L prothioconazole) @ 0.5 L/ha; A-15-14-02 (250 g/L difenoconazole) @ 0.5 L/ha; A-15-1-404 (250 gl/L difenoconazole\u0026thinsp;+\u0026thinsp;250 gl/L mandipropamid) @ 0.6 L/ha; A-18-14-01 Belanty (75 g/Lmefentriconazole) @ 1.25 L/ha\u003c/p\u003e \u003cp\u003eA-15-7-01 (83 g/L zoxamide\u0026thinsp;+\u0026thinsp;667 g/L mancozeb) @ 1.8 kg/ha; A-15-7-04 (75 g/L fenamidone\u0026thinsp;+\u0026thinsp;375 g/L propamocarb) @ 2.0 L/ha ; A-15-7-06 (150 g/L azoxystrobin\u0026thinsp;+\u0026thinsp;375 g/L fluazinam) @ 0.5 L/ha; A-15-7-08 (dimethomorph\u0026thinsp;+\u0026thinsp;mancozeb) @ 2.0 kg/ha.\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eThe aim of the experiments was to rate the efficacy of fungicides to control foliar blight, tuber blight and early blight using data generated from multi-year and multi-country field experiments with standard protocols instead of a consensus of expert judgement. The ratings could be used by growers, extension services and scientists to develop efficient control strategies based on the quantitative characteristics of the fungicides tested. During a EuroBlight meeting it was decided that a rating could only be awarded if the fungicide being tested was in a minimum of six successful experiments. Furthermore, the experiments should have been conducted in at least 3 different countries and for a minimum of 2 growing seasons. More than 6 experiments were allowed, however each additional valid experiment was to be included in the rating calculation. An experiment was considered not valid if the disease severity did not exceed the threshold of 10% disease severity in the worst treatment (most often the reference treatment).\u003c/p\u003e \u003cp\u003eIn the calculations for foliar and tuber blight ratings presented here, only fungicides registered in the EU were used. Although mancozeb is not registered in the EU anymore, this fungicide was almost always used as a reference; the exception was for the tuber blight experiment in the Netherlands in 2009. More fungicides, i.e. those that are still approved outside of the EU, are included in the database and have their ratings published on the EuroBlight website. For early blight all registered fungicides were used in the calculations.\u003c/p\u003e \u003cdiv id=\"Sec12\" class=\"Section2\"\u003e \u003ch2\u003eFungicide resistance\u003c/h2\u003e \u003cp\u003eIn the experiments fungicides were sprayed season long, or shorter during the relevant period in case of tuber blight and early blight. Spraying fungicides was usually not according to the label and not according to the FRAC guidelines pertaining to fungicide resistance management for \u003cem\u003eP. infestans\u003c/em\u003e and \u003cem\u003eA. solani\u003c/em\u003e. However, it was in accordance with EPPO guidelines for registration purposes. Repeated sprays with the same fungicide might select for fungicide resistance (Gr\u0026uuml;nwald et al., \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2006\u003c/span\u003e); this must be avoided for commercial crops because of their very large hectarage. In 2006 when the first foliar blight experiments took place only resistance to metalaxyl (Davidse et al., \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e1981\u003c/span\u003e) was known. During the next 20 years resistance or reduced sensitivity was also found for fluazinam (Schepers et al., \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e2018\u003c/span\u003e), mandipropamid (Abuley et al, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2023\u003c/span\u003e), and oxysterol binding protein fungicides (OSBP) (Anonymous, \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2024a\u003c/span\u003e) in the \u003cem\u003eP. infestans\u003c/em\u003e population. For the \u003cem\u003eA. solani\u003c/em\u003e population resistance has been described for two FRAC groups: quinone outside inhibitors (Gudmestad, et al., \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2013\u003c/span\u003e; Leiminger et al.,2013) and succinate dehydrogenase inhibitors (Wharton et al., \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2012\u003c/span\u003e; Landschoot et al., \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2017\u003c/span\u003e). On the EuroBlight website it is stated that \u0026ldquo;Ratings can be lower where resistant isolates are present, depending on their frequency and the mechanism of resistance, leading to variable impact on product efficacy. Resistance management strategies should always be implemented as part of Integrated Disease Management, regardless of the absence or presence of resistance. Please refer to the FRAC website for the corresponding resistance management guidelines.\u0026rdquo; If fungicide resistance occurred within a ratings experiment, the data for any product containing the affected fungicide active(s) were considered invalid. This is because the aim was to rate potential efficacy.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec13\" class=\"Section2\"\u003e \u003ch2\u003eFoliar blight\u003c/h2\u003e \u003cp\u003eThe reference treatment mancozeb is a multisite fungicide (coded M 03) (Anonymous, 2024b) and thus less prone to fungicide resistance development within the \u003cem\u003eP. infestans\u003c/em\u003e population. Therefore, it was expected that the performance of mancozeb throughout the years would be stable and it was decided to make its rating a constant, 2.0. In the first EuroBlight tables a scale of - to +++ was used. For the quantitative ratings we opted for a similar range, 2.0 to 5.0. A rating of 5.0 represents no visible lesions on the foliage. Theoretically a rating lower than 2.0 would be possible, however during the years of the experiments such a rating has not been published in the EuroBlight table. It must be noted that a rating is only published after the fungicide meets the test requirements and there is agreement between the managers of the crop protection company and of the EuroBlight trials.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec14\" class=\"Section2\"\u003e \u003ch2\u003eTuber blight\u003c/h2\u003e \u003cp\u003eNo untreated control was included but it would have been an unsuitable reference because the foliar blight epidemic in untreated plots is fast, resulting in too short a period with a sufficiently sporulating canopy. For tubers to become infected the presence of large numbers of sporangia on the haulm and precipitation/irrigation is necessary. The more the epidemic is prolonged the more opportunity for tuber infection to occur. Several publications comment on there being low incidences of tuber blight after a strong foliar blight epidemic with early haulm death (Gray, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e1958\u003c/span\u003e; Fehrmann, \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e1963\u003c/span\u003e; Hirst et al., \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e1965\u003c/span\u003e; Ullrich, \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e1967\u003c/span\u003e; Bochow et al., \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e1979\u003c/span\u003e). Therefore, in the tuber blight trials, mancozeb was chosen as the reference treatment. Based on expert judgment it was expected that mancozeb was not able to control tuber blight, thus by definition its rating should be a constant 0.0. The maximum rating was set at 5.0. This could only be achieved if no tuber blight was found in any of the minimum of 6 experiments in which the candidate fungicide was tested.\u003c/p\u003e \u003cp\u003eThe severity of 0.5% was considered the optimum severity of blight to start with the first application of the test candidate. Lower than this would most likely result in the tuber blight incidences being confounded by markedly different foliar epidemic curves for the candidates. Delaying the first application of the test fungicides until leaf blight was substantially greater than 0.5% risked an unwelcome, high background incidence of tuber blight in all treatments.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec15\" class=\"Section2\"\u003e \u003ch2\u003eEarly blight\u003c/h2\u003e \u003cp\u003eIn contrast to late blight, in the early blight rating experiments the untreated control was accepted as the reference treatment. Obviously, the untreated control shows no efficacy in controlling \u003cem\u003eA. solani\u003c/em\u003e and therefore it is rated 0.0. There are fungicides specifically targeted at \u003cem\u003eA. solani\u003c/em\u003e, which usually are sprayed at 14-day intervals. There are also fungicides aimed at \u003cem\u003eP. infestans\u003c/em\u003e, but with a side effect on \u003cem\u003eA. solani.\u003c/em\u003e These fungicides are normally sprayed every 7 days. In the EuroBlight table these two groups are listed separately.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec16\" class=\"Section2\"\u003e \u003ch2\u003eEuroBlight Table\u003c/h2\u003e \u003cp\u003eFungicide ratings have been published from within a few years of the ratings trials starting. The table has been developed over many years, with new data added almost every year. However, ratings when published were fixed. In the UK five independent trials validated the accuracy of the EuroBlight ratings for the fungicides tested, especially if curative ratings were also taken into account (Bain et al., \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2017\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eIn conclusion, this study has described a systematic approach to rating the efficacy of fungicides. The data used in this study were generated over several growing seasons (2006\u0026ndash;2023) and in four different countries (Denmark, the Netherlands, Germany, and the United Kingdom). The method stipulates that a fungicide can only be rated if there are results from successful replicated field experiments conducted over at least two growing seasons, using a susceptible variety, and in at least three different European countries. Additionally, spatially uniform disease pressure, achievable through the inclusion of spreader rows and the maintenance of a disease-conducive environment (e.g., by misting the field via sprinkler irrigation), is necessary to ensure a successful experiment. Importantly, the procedure allows ratings to be calculated even although candidate fungicides are tested in different years. Overall, the method developed and validated in this study is robust and provides an objective procedure for deriving numeric ratings for fungicides, not just for potato late blight and early blight, but also for other host-pathosystems.\u003c/p\u003e \u003c/div\u003e"},{"header":"Statements and Declarations","content":"\u003cp\u003eThe authors declare no competing interests.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis research was funded by crop protection companies (Adama, Bayer CropScience, BASF, Belchim Crop Protection, Certis Europe BV, Certis Belchim, Corteva, Dow AgroSciences, FMC, Gowan, Indofil Industries LTD, Isagro Ricera S.r.l., ISK, Nissan Chemical Europe SAS, Nufarm, Oxon, Syngenta, UPL) who submitted fungicides to be rated and included in the EuroBlight fungicide table. The authors would also like to thank Nick Bradshaw and Bent J\u0026oslash;rgen Nielsen for their contribution to the protocols and the set-up of the initial experiments. The authors would like to thank the late Wim van den Berg for helping to put the necessary statistical procedures in place.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eAbuley, IK, Hansen, JG (2021). An epidemiological analysis of the dilemma of plant age and late blight (\u003cem\u003ePhytophthora infestans\u003c/em\u003e) susceptibility in potatoes. Eur J Plant Pathol 161, 645\u0026ndash;663. https://doi.org/10.1007/s10658-021-02350-4\u003c/li\u003e\n\u003cli\u003eAbuley IK, Lynott JS, Hansen JG, Cooke DEL, Lees AK. (2023). The EU43 genotype \u003cem\u003eof Phytophthora infestans\u003c/em\u003e displays resistance to mandipropamid. Plant Pathology 72 (7): 1305-1313 https://doi.org/10.1111/ppa.13737\u003c/li\u003e\n\u003cli\u003eAnonymous (2020). Efficacy evaluation of fungicides. PP 1/002(5) \u003cem\u003ePhytophthora infestans\u003c/em\u003e on potato. Bulletin OEPP/EPPO Bulletin (2020) 0 (0), 1\u0026ndash;4. DOI: 10.1111/epp.12708\u003c/li\u003e\n\u003cli\u003eAnonymous (2008). Efficacy evaluation of fungicides. PP1/263 (1) \u003cem\u003eAlternaria solani\u003c/em\u003e and \u003cem\u003eAlternaria alternata\u003c/em\u003e on potato and outdoor production of tomato. European and Mediterranean Plant Protection Organization.\u003c/li\u003e\n\u003cli\u003eAnonymous (2024a). Minutes of the FRAC OSBPI Working Group Meeting 7 February 2024. OSBPI Working Group FRAC.\u003c/li\u003e\n\u003cli\u003eAnonymous (2024a). FRAC Code List\u0026copy;* 2024: Fungal control agents sorted by cross-resistance pattern and mode of action.\u003c/li\u003e\n\u003cli\u003eBain RA, Schepers H, Nielsen B, Bradshaw N (2009). Protocol for testing \u0026ldquo;Effectiveness: tuber blight\u0026rdquo; (\u003cem\u003ePhytophthora infestans\u003c/em\u003e).\u003c/li\u003e\n\u003cli\u003eBain RA, Kenndy C, Kiltie D (2017). Foliar late blight development in the UK in relation to EuroBlight fungicide efficacy ratings. PAGV \u0026ndash; SPECIAL REPORT NO 18 \u0026ndash; 2017, 269-272.\u003c/li\u003e\n\u003cli\u003eBochow H, Krochert R, Tarnow W. (1979) Hinweise auf einige das Auftreten und die Bek\u0026auml;mpfung der Kartoffelbraunf\u0026auml;ule (Phytophthora infestans) betreffende Zusammenh\u0026auml;nge. Nachrichtenblatt Pflanzenschutzdienst DDR 24, 225-229.\u003c/li\u003e\n\u003cli\u003eCampbell CL, Madden LV (1990). Introduction to Plant Disease Epidemiology. John Wiley \u0026amp; Sons, New York. 532 p.\u003c/li\u003e\n\u003cli\u003eCooke LR, Schepers HTAM, Hermansen A, Bain RA, Bradshaw NJ, Ritchie F, Shaw DS, Evenhuis A, Kessel, GJT, Wander JGN, Andersson B, Hansen JG, Hannukkala A, N\u0026aelig;rstad R, Nielsen BJ (2011). Epidemiology and integrated control of potato late blight in Europe. \u003cem\u003ePotato Research 54\u003c/em\u003e, 183-222. https://doi.org/10.1007/s11540-011-9187-0\u003c/li\u003e\n\u003cli\u003eDavidse LC, Looijen D, Turkensteen LJ, Van der Wal D. (1981). Occurrence of metalaxyl-resistant strains of \u003cem\u003ePhytophthora infestans\u003c/em\u003e in Dutch potato fields. Netherlands Journal of Plant Pathology 87, 65\u0026ndash;68. https://doi.org/10.1007/BF01976658\u003c/li\u003e\n\u003cli\u003eEvenhuis B, Leiminger J, Nielsen B, Hausladen H, Spoelder J, Kapsa, J, Vanhaverbeke P, Shtienberg, D, Schepers H (2019) Protocol for testing effectiveness to control early blight. EuroBlight meeting York\u003c/li\u003e\n\u003cli\u003eEllis MB, Gibson IAS (1975). \u003cem\u003eAlternaria solani.\u003c/em\u003e Descriptions of fungi and bacteria 48, sheet 475. https://doi.org/10.1079/DFB/200564004\u003c/li\u003e\n\u003cli\u003eFehrmann, H. (1963) Untersuchungen zur Pathogenese der durch Phytophthora infestans hervorgerufenen Braunf\u0026auml;ule der Kartoffelknolle. Phytopath. Z. 46, 371-408\u003c/li\u003e\n\u003cli\u003eGray, E.G. (1958): The control of blight in potato crops. Scottish Agric. 38, 46-47.\u003c/li\u003e\n\u003cli\u003eGr\u0026uuml;nwald NJ, Sturbaum AK, Montes GR, Serrano EG, Lozoya-Salda\u0026ntilde;a H, Fry WE (2006). Selection for fungicide resistance within a growing season in field populations of \u003cem\u003ePhytophthora infestans\u003c/em\u003e in the center of origin. \u003cem\u003ePhytopathology 96\u003c/em\u003e, 1397-1403.\u003c/li\u003e\n\u003cli\u003eGudmestad NCS, Arabiat S, Pasche JS, Miller, JS (2013). Prevalence and impact of SDHI fungicide resistance in \u003cem\u003eAlternaria solani\u003c/em\u003e. Plant Dis. 97:952-960.\u003c/li\u003e\n\u003cli\u003eLeiminger JH, Adolf B, Hausladen H (2013) Occurrence of the F129L mutation in Alternaria solani populations in Germany in response to QoI application, and its effect on sensitivity. First published: 29 July 2013 https://doi.org/10.1111/ppa.12120Cit\u003c/li\u003e\n\u003cli\u003eHaverkort AJ, Boonekamp PM, Hutten R, Jacobsen E, Lotz LAP, Kessel GJT, Visser RGF, van der Vossen EAG (2008) Societal costs of late blight in potato and prospects of durable resistance through cisgenic modification. Potato Res 51:47\u0026ndash;57.\u003c/li\u003e\n\u003cli\u003eHirst, JM, Stedman OJ, Lacey J, Hide GA (1965) The epidemiology of \u003cem\u003ePhytophthora infestans\u003c/em\u003e. IV. Spraying trails, 1959 to 1963, and the infection of tubers. Ann. appl. Biol. 55, 373-395.\u003c/li\u003e\n\u003cli\u003eMontgomery DC, Peck EA. (1982). Introduction to Linear Regression Analysis. John Wiley \u0026amp; Sons. New York.\u003c/li\u003e\n\u003cli\u003eLandschoot S, Carrette J, Vandecasteele M, De Baets B, Hofte M, Audenaert K, Haesaert G (2017). Boscalid-resistance in \u003cem\u003eAlternaria alternata\u003c/em\u003e and \u003cem\u003eAlternaria solani \u003c/em\u003epopulations: An emerging problem in Europe. Crop Protection 92 (2017) 49-59.\u003c/li\u003e\n\u003cli\u003ePayne RW. (2009). GenStat. WIREs Computational Statistics Volume 1, Issue 2, Sep 2009: 131-260. https://doi.org/10.1002/wics.32\u003c/li\u003e\n\u003cli\u003eSchepers HTAM, Evenhuis A, Spits, H. G. (2009). Strategies to control late blight in potatoes in Europe. Acta Horticulturae, (834), 79\u0026ndash;82.\u003c/li\u003e\n\u003cli\u003eSchepers HTAM, Kessel GJT, Lucca F, F\u0026ouml;rch MG, Van den Bosch GBM, Topper CG, Evenhuis A. (2018). Reduced sensitivity of fluazinam against \u003cem\u003ePhytophthora infestans\u003c/em\u003e in the Netherlands. \u003cem\u003eEuropean Journal of Plant Pathology 151\u003c/em\u003e, 947-960.\u003c/li\u003e\n\u003cli\u003eSchepers H, Nielsen B, Bradshaw N, Bain RA (2007). Effectiveness of fungicides against foliage blight caused by \u003cem\u003ePhytophthora infestans\u003c/em\u003e. Euroblight Protocol \u0026ndash; Version 1.0 \u0026ndash; 30 October 2007. https://agro.au.dk/fileadmin/Effectiveness_leaf_late_blight.pdf\u003c/li\u003e\n\u003cli\u003eUllrich J. (1967) Die Braunf\u0026auml;ule der Kartoffel (Phytophthora infestans [Mont.] de Bary). Nachrichtenblatt Deut. Pflanzenschutzd. (Braunschweig) 19, 55-59.\u003c/li\u003e\n\u003cli\u003eWharton P, Fairchild K, Belcher A, Wood E, (2012). First report of in vitro boscalid resistant isolates of \u003cem\u003eAlternaria solani\u003c/em\u003e causing early blight of potato in Idaho. Plant Dis. 96, 454.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":true,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"potato-research","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"potr","sideBox":"Learn more about [Potato Research](http://link.springer.com/journal/11540)","snPcode":"11540","submissionUrl":"https://www.editorialmanager.com/potr/default2.aspx","title":"Potato Research","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Phytophthora infestans, Alternaria solani, Solanum tuberosum, crop protection","lastPublishedDoi":"10.21203/rs.3.rs-6305294/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6305294/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eLate blight\u003cem\u003e (Phytophthora infestans\u003c/em\u003e) and\u003cem\u003e \u003c/em\u003eearly blight\u003cem\u003e (Alternaria solani) \u003c/em\u003eare the most important diseases in potato cultivation. The control of these diseases depends largely on fungicide sprays during the growing season. Fungicides differ in their efficacy to control any pathogen. The use of effective fungicides is necessary for both the control of the disease and to avoid unnecessary sprays. Each active ingredient has its own efficacies and specific characteristics, which are expressed in fungicide products. A EuroBlight fungicide table was set up to provide an overview of the relative ratings for each characteristic for different fungicides used to control late blight or early blight. Until 2007 EuroBlight fungicide ratings were based on the judgement of experts from the crop protection companies and independent researchers. To objectively evaluate the effectiveness of fungicides, harmonised protocols were discussed, and it was proposed that the ratings of fungicides for the EuroBlight fungicide table were to be calculated, based on results from field experiments carried out over 2 years and in at least 3 European countries. Fungicide ratings derived from the experiments, which indicate the efficacy of fungicides to control potato late blight (foliar and tuber blight) or early blight, were published on the EuroBlight website from 2008. This paper describes the experimental procedure as well as statistical analyses used to derive the EuroBlight fungicide ratings. The procedure allows ratings to be calculated even although candidate fungicides are tested in different years. Overall, the method developed and validated in this study is robust and provides an objective procedure for deriving numeric ratings for fungicides, not just for potato late blight and early blight, but also for other host-pathosystems.\u003c/p\u003e","manuscriptTitle":"Methodology to determine fungicide efficacy ratings for the EuroBlight tables – potato late or early blight","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-05-13 06:59:24","doi":"10.21203/rs.3.rs-6305294/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Minor revisions","date":"2025-10-14T16:08:22+00:00","index":"","fulltext":""},{"type":"reviewerAgreed","content":"","date":"2025-05-09T12:16:59+00:00","index":0,"fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-05-08T09:49:22+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"Potato Research","date":"2025-04-25T17:15:39+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-04-25T17:01:17+00:00","index":"","fulltext":""},{"type":"submitted","content":"Potato Research","date":"2025-04-23T11:16:05+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"potato-research","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"potr","sideBox":"Learn more about [Potato Research](http://link.springer.com/journal/11540)","snPcode":"11540","submissionUrl":"https://www.editorialmanager.com/potr/default2.aspx","title":"Potato Research","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"f2df0124-4cd5-499b-bb65-5e3f521eefeb","owner":[],"postedDate":"May 13th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2026-03-16T16:00:52+00:00","versionOfRecord":{"articleIdentity":"rs-6305294","link":"https://doi.org/10.1007/s11540-026-10014-1","journal":{"identity":"potato-research","isVorOnly":false,"title":"Potato Research"},"publishedOn":"2026-03-13 15:57:51","publishedOnDateReadable":"March 13th, 2026"},"versionCreatedAt":"2025-05-13 06:59:24","video":"","vorDoi":"10.1007/s11540-026-10014-1","vorDoiUrl":"https://doi.org/10.1007/s11540-026-10014-1","workflowStages":[]},"version":"v1","identity":"rs-6305294","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6305294","identity":"rs-6305294","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}