Control Of Potato Late Blight Research Articles

Opportunity of the NEGFRY Decision Support System for the Sustainable Control of Potato Late Blight in A Limia (NW of Spain)

The NEGFRY system is presented in this research work as a novelty strategy for the control of potato late blight in A Limia (NW Spain). The aim was to analyse the number of fungicide applications established by NEGFRY (Decision Support System, DSS) with respect to the routine calendars of this potato production area. This approach is in accordance with the requirements imposed by European policies, participating in more profitable and environmentally friendly agriculture. For this purpose, the relationships between the pathogen and the environmental conditions and epidemiological parameters were analysed in different plots compared to late blight infection in both Routine and DSS strategies. In addition, economic and environmental impacts of fungicide sprays were also analysed to check the adaptability of the decision support system to late blight in the area. Results confirmed that it is possible to reduce sprays following the NEGFRY model by more than 50% compared with Routine applications. Therefore, NEGFRY is a promising strategy to achieve lower footprint potato yields through a reduction in applied pesticides and water, lower gas emissions and less soil compaction due to a reduction in the number of tractor passes over the soil. The commitment to this strategy contributes to improving the economy of farmers, the health of the biodiversity, the environment and consumers, as well as to comply with demands of global economies in terms of more sustainable and resilient agriculture.

Enhancing Potato Late Blight Control: Triffa Plain Model Assessment (Eastern Morocco)

Potato late blight Phytophthora infestans is a serious potato disease. In eastern Morocco and more precisely in the Triffa plain, late blight ravages potato fields, causing severe losses of up to 80%. Chemical control remains the most effective, easiest and most commonly used means of control by farmers in the region. However, abusive use and the high frequency of treatments pose real problems for consumers and the environment. The objective of this work was to test certain downy mildew monitoring models for better optimization of fungicide use. A study was carried out in the Triffa plain to test potato late blight monitoring models on three potato varieties, Mondial, Désirée and Spunta. Two models have made it possible to save up to 50% of the costs linked to chemical treatments against mildew and, among other things, help to preserve the environment.

Exogenous dsRNA-Induced Silencing of the Phytophthora infestans Elicitin Genes inf1 and inf4 Suppresses Its Pathogenicity on Potato Plants.

Phytophthora infestans, an Oomycete pathogen, has a devastating impact on potato agriculture, leading to the extensive use of chemical fungicides to prevent its outbreaks. Spraying double-stranded RNAs to suppress specific genes of the pathogen via the RNA interference (RNAi) pathway may provide an environmentally friendly alternative to chemicals. However, this novel approach will require various target genes and application strategies to be tested. Using the L4440 backbone, we have designed two plasmids to express dsRNA targeting inf1 and inf4 genes of P. infestans that are known to contribute to the disease development at different stages. The dsRNA produced by the bacteria was tested on potato explants and demonstrated a statistically significant reduction in lesions five days after inoculation compared to water treatment. The study results allow us to consider our approach to be promising for potato late blight control.

Biological control of potato late blight with a combination of Streptomyces strains and biochar

Potato late blight (PLB) caused by Phytophthora infestans is the most damaging disease in potatoes. In this study, Streptomyces and biochar (a new eco-material with the potential to improve soil and plant health) were used for the biological control of PLB. In vitro experiments showed that the six Streptomyces strains can significantly inhibit the growth of P. infestans and sporangia germination. In vivo tests showed that the six Streptomyces strains significantly inhibited the infection of P. infestans on potato tubers. After combined with biochar, the inhibition rate of Streptomyces strains against P. infestans was increased by 1.9 % to 46.1 %. In two years of field trials, the combination of six Streptomyces strains and biochar decreased the disease index by 10 % to 26 %, exhibiting better disease control than the use of either agent alone. In addition, a single application of biochar did not significantly decrease the incidence of the disease but enriched the rhizosphere in the beneficial bacterium Rhizobium. Our results highlight the potential for biological control of PLB with a combination of Streptomyces strains and biochar.

Mesoporous Silica Nanoparticles Induce Intracellular Peroxidation Damage of Phytophthora infestans: A New Type of Green Fungicide for Late Blight Control.

Nanopesticides are considered to be a promising alternative strategy for enhancing bioactivity and delaying the development of pathogen resistance to pesticides. Here, a new type of nanosilica fungicide was proposed and demonstrated to control late blight by inducing intracellular peroxidation damage to Phytophthora infestans, the pathogen associated with potato late blight. Results indicated that the structural features of different silica nanoparticles were largely responsible for their antimicrobial activities. Mesoporous silica nanoparticles (MSNs) exhibited the highest antimicrobial activity with a 98.02% inhibition rate of P. infestans, causing oxidative stress responses and cell structure damage in P. infestans. For the first time, MSNs were found to selectively induce spontaneous excess production of intracellular reactive oxygen species in pathogenic cells, including hydroxyl radicals (•OH), superoxide radicals (•O2-), and singlet oxygen (1O2), leading to peroxidation damage in P. infestans. The effectiveness of MSNs was further tested in the pot experiments as well as leaf and tuber infection, and successful control of potato late blight was achieved with high plant compatibility and safety. This work provides new insights into the antimicrobial mechanism of nanosilica and highlights the use of nanoparticles for controlling late blight with green and highly efficient nanofungicides.

Isolation and Screening of Antagonistic Endophytes against Phytophthora infestans and Preliminary Exploration on Anti-oomycete Mechanism of Bacillus velezensis 6-5

Phytophthora infestans, the notorious pathogen of potato late blight, leads to a severe decline in potato yields and even harvest failure. We isolated 201 endophytic isolates from healthy root tissues of potatoes, among which 41 showed strong antagonistic activity against P. infestans. Further, the tolerance to stress and the potential application against potato late blight of these antagonistic isolates were tested. Most of them were extremely tolerant to stresses such as acid-alkali, temperature, UV, salt, and heavy metal stress. However, some antagonistic isolates with excellent stress tolerance might be pathogenic to potatoes. Combining the screening results, a total of 14 endophytes had excellent comprehensive performance in all the tests. In this paper, the endophyte 6-5 was selected among them for the preliminary exploration of the anti-oomycete mechanism. Analysis of the 16S rDNA sequence revealed that 6-5 had a high homology to the corresponding sequence of Bacillus velezensis (99.72%) from the NCBI database. Endophyte 6-5 significantly inhibited the mycelial growth of P. infestans, with an inhibition rate of over 90% in vitro assays, and deformed the hyphal phenotype of P. infestans. In addition, endophyte 6-5 could secrete protease and cellulase, and produce antagonistic substances with high thermal stability, which might be helpful to its antagonistic activity against P. infestans. Furthermore, it was demonstrated that 6-5 had the ability to improve the resistance of potato tubers to late blight. In short, our study described the process of isolating and screening endophytes with antagonistic activity against P. infestans from potato roots, and further explored the potential of biocontrol candidate strain 6-5 in potato late blight control.

Effects of Combination of Copper Fungicide and Plant Activator on Late Blight and Quality Criteria of Potato

Late blight caused by Phytophthora infestans is one of the most important fungal diseases that cause damage to both the green parts and tuber of the potato plant and limits potato cultivation. Systemic fungicides are mostly preferred by farmers in the control of potato late blight. The fact that systemic fungicides cause health problems in terms of human and environmental health has revealed the need for research on control methods that do not threaten environmental health. In recent years, successful results have been obtained in the control of many diseases with plant activators known as Induced Systemic Resistance (ISR) promoters. This study was carried out in the spring season of 2016-2017 to observe the effect of copper fungicide and plant activator (Lactobacillus acidophilus fermentation product) combination on the control of potato late blight disease and some quality criteria of potato tubers in the experimental plots of Ege University Ödemiş Vocational School in Ödemiş district of İzmir province. The experiment was planned as two separate experiments with Marabel and Melody potato cultivars. The experiment was established according to a split-plot experimental design with four replications. In this study, the effect of the treatments on potato quality and yield criteria such as tuber number, tuber width, tuber length, single tuber weight, yield per decare, and the effects of the pesticides on potato late blight disease and disease severity parameters were evaluated. When the data obtained as a result of the study were evaluated, it was determined that the combination application had a positive effect on the control of potato late blight disease in both potato cultivars compared to the control plots. When the quality criteria of potato tubers were evaluated, the highest number of tubers was obtained from the plots where copper fungicide and plant activator (Isr-2000) combination was applied. Significant increase was obtained in potato quality and yield criteria such as tuber width, tuber length, average tuber weight and yield per decare when the combination plots were compared with the control plots. In conclusion, the use of contact fungicides and plant activator combinations in the control of late blight in the spring period within the scope of sustainable agriculture is promising as an application alternative in the control of plant diseases in organic agriculture.

Biological control of potato late blight by Streptomyces sp. FXP04 and potential role of secondary metabolites

Potato late blight, caused by the oomycete Phytophthora infestans, is a devastating disease of potato globally. Antagonistic microorganisms have been used as biological control agents to inhibit P. infestans and reduce the use of synthetic fungicides. In the present study, a bacterial isolate (FXP04) was obtained from the rhizosphere soil of potato plants and demonstrated to significantly inhibit the mycelial growth of P. infestans in vitro. In a pot experiment, application of FXP04 to potato tubers prior to planting and to the soil after planting decreased both disease incidence and the disease index of potato late blight. Analysis of the 16S rDNA sequence of FXP04 indicated that the strain belonged to the genus, Streptomyces, and thus the strain was named Streptomyces sp. FXP04. The genome of Streptomyces sp. FXP04 was sequenced to determine the presence of gene clusters encoding secondary metabolites. AntiSMASH software analysis identified 15 gene clusters responsible for the biosynthesis of secondary metabolites, including the antimicrobial compound, Piericidin A. Metabolomic analysis of the fermentation broth of Streptomyces sp. FXP04 identified the presence of Piericidin A. Additional experiments indicated that Piericidin A inhibited the mycelial growth of P. infestans. The results of our study indicate that Streptomyces sp. FXP04 represents a potential biocontrol agent that could be used to control potato late blight. Furthermore, Piericidin A may represent the antimicrobial secondary metabolite responsible for the biological control activity of Streptomyces sp. FXP04.

Opportunities for Improved Potato Late Blight Management in the Republic of Ireland: Field Evaluation of the Modified Irish Rules Crop Disease Risk Prediction Model.

Potato late blight remains the most significant disease threat of potato cultivation globally, often requiring expensive, time-consuming, and environmentally unfriendly approaches to disease management. The goal of this research was to evaluate whether an estimation of potato late blight risk based on environmental factors can be reliably used to adjust the standard potato late blight management practices and the role of cultivar resistance under growing conditions and contemporary Phytophthora infestans populations in the Republic of Ireland. The modified Irish Rules model made it possible to reduce fungicide usage by 58.7% on average, compared with current standard practices used by growers and without adversely compromising disease control and yield, with similar results achieved by the half-dose program. Host resistance levels were found to be correlated with a delay in the initiation of the epidemics, final foliar disease levels, and reduction of fungicide usage. Disease levels on the highly resistant cultivars remained low, and a clear selection pattern toward the P. infestans genotypes EU_13_A2 and EU_6_A1 was observed. An increase in the frequency of strains belonging to genotypes EU_13_A2 and EU_6_A1 was also observed to occur in the latter part of the trial growing seasons. Because of the increasingly dynamic nature of the population structure, associated with the continued evolution of the P. infestans population and the arrival of EU_36_A2 in the Republic of Ireland, routine population monitoring is necessary to ensure that potato late blight control strategies remain effective.[Formula: see text] Copyright © 2021 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

English

This study aimed to screen myxobacteria strains with strong activity against Phytophthora infestans and to study its secondary metabolites. Myxobacteria were isolatedfrom a soil sample using the rabbit feces as bait. A strain inhibitive to P. infestanswas identified by morphological observation and 16S rRNA sequence analysis. The fermentation parameters were optimized through a combination of univariate analysis and orthogonal optimization. The stability and antimicrobialactivities of the secondary metabolites were determined using the filter paper method, and the effects on the development of the potato late blight and its pathogen were determined using the in vitroleaf method. The myxobacteria B25-I-1 isolated from a soil sample showed strong activity against P. infestansand was identified as Myxococcus xanthus. The optimal fermentation conditions of M. xanthusB25-I-1 were as follows: inoculum size of 10%, shaking at 180 rmin-1, incubation temperature of 32°C, and incubation time of 8 days. The secondary metabolites were highly tolerant to high temperature, treatment with protease K, andultraviolet and natural lights. Besides P. infestans, the secondary metabolites also showed variant antagonistic effects againstEscherichia coli,Staphylococcus aureus,Bacillus subtilis,Saccharomyces cerevisiae,Fusarium oxysporum, Rhizoctonia solani, and Sclerotinia sclerotiorum. The results of the potato late blight control on potato leaves indicated that the secondary metabolites could significantly inhibit the infection of detached potato leaves caused by P. infestansand caused no damage to the leaves of different varieties of potatoes by themselves. This study provides basic data for the the development of a biopesticide against potato late blight.© 2021 Friends Science Publishers

Antagonistic Activity of Bacillus velezensis SDTB038 against Phytophthora infestans in Potato.

Potato late blight is a severe and highly epidemic disease caused by Phytophthora infestans that can affect all parts of the plant. This study mainly screened antagonistic strains for good control of potato late blight and identified strain SDTB038 as Bacillus velezensis according to its morphological and chemical properties and the 16S rRNA, gyrA, and gyrB gene sequences. This antagonistic strain achieved good control of potato late blight in greenhouses and fields and promoted potato plant growth. Two-year field trials (2018 and 2019) showed that B. velezensis SDTB038 can be used to reduce food losses caused by late blight, achieving late blight reductions of 40.79% (2018) and 37.67% (2019). In two-year field trials, the control effects of the highest concentrations of fluopimomide and B. velezensis SDTB038 were better than those of the other treatments. The control effect of 85 g ha-1 fluopimomide and B. velezensis SDTB038 and that of 170 g ha-1 fluopimomide alone showed no significant differences. These field results indicate that a low concentration of fungicide and a high concentration of SDTB038 can be effective in controlling potato late blight. Foliar detection showed that lipopeptides have an inhibitory effect on P. infestans. The amplification of lipopeptide genes revealed surfactin (srfAB and srfAC) and fengycin (fenB) genes in SDTB038, but only surfactin production by B. velezensis SDTB038 was observed by ultra-high-performance liquid chromatography-quadrupole-time-of-flight mass spectrometry analysis. Therefore, the strain B. velezensis SDTB038 can produce secondary metabolites that help potato plants resist late blight development, can effectively inhibit the infection of potato leaves by P. infestans, and has potential value for development as a biological pesticide against potato late blight.

Biocontrol mechanism of Myxococcus fulvus B25-I-3 against Phytophthora infestans and its control efficiency on potato late blight.

Phytophthora infestans is the pathogen of potato late blight, which is one of the most serious diseases of the potato. Myxobacteria, especially Myxococcus, become a valuable biological control resource due to their preponderant abilities to produce various secondary metabolites with novel structure and remarkable biological activity. In a previous study, Myxococcus fulvus B25-I-3 with antagonistic activity against P. infestans was isolated from an environmental sample by rabbit fecal induction method. The biocontrol mechanism of M. fulvus B25-I-3 against P. infestans and its control efficiency on potato late blight were studied. The results showed that the active substances produced by strain B25-I-3 had strong inhibitory effect on the asexual reproduction and sexual reproduction of P. infestans. In addition, the active substances could reduce the content of soluble proteins and the activity of the protective enzymes (polyphenol oxidase, peroxidase, phenylalanine ammonia lyase, superoxide dismutase) in P. infestans and increase the oxidative damage and permeability of cell membrane. And the active substances could inhibit the infection of the detached potato leaves by P. infestans significantly. In conclusion, M. fulvus B25-I-3 can produce active substances against P. infestans and has potential value to develop into biological pesticides for the control of potato late blight. The completion of this work may provide basic data for the isolation and identification of active substances and the development of pesticides against potato late blight.

Biocontrol mechanism of Myxococcus xanthus B25-I-1 against Phytophthora infestans

Phytophthora infestans is the pathogen causing potato late blight, one of the most serious diseases of potato. Myxobacteria have become a valuable biological control resource due to their preponderant abilities to produce various secondary metabolites with novel structure and remarkable biological activity. In this study, Myxococcus xanthus strain B25-I-1, which exhibited strong antagonistic activity against P. infestans, was isolated from soil sample and identified by 16S rRNA sequence analysis. The strain exhibited antagonistic activity against several species of fungus and bacteria. Analysis of the biocontrol mechanism showed that the active extract produced by strain B25-I-1 had strong inhibitory effects on mycelium and the asexual and sexual reproductive structures of P. infestans. Furthermore, these active extract decreased the content of soluble proteins and activity of the protective enzymes (PPO, POD, PAL, and SOD), increased the oxidative damage and the permeability of the cell membrane in P. infestans. All of these mechanisms might be the biocontrol mechanism of B25-I-1 against P. infestans. The active extract of strain B25-I-1 was separated by TLC and HPLC, and the components with antibiotic activity were detected by HPLC-MS. It was found that the antagonistic components of B25-I-1 contained methyl (2R)-2-azido-3-hydroxyl-2-methylpropanoate and N-(3-Amino-2-hydroxypropyl)-N-methylsulfuric diamide. The active extract significantly inhibited the infection on detached potato leaves by P. infestans, and these substances did not cause damage to the potato leaves. In conclusion, M. xanthus B25-I-1 produced active extract against P. infestans and might potentially be a candidate to develop into biological pesticides for the control of potato late blight. This study adds to the literature on the isolation and identification of active extracts from myxobacteria, and B25-I-1 in particular, for cures or treatments to potato late blight.

Integrated control of potato late blight with a combination of the photosynthetic bacterium Rhodopseudomonas palustris strain GJ-22 and fungicides

Late blight caused by the oomycete Phytophthora infestans is the major yield-threatening disease in potato production. An isolate of the photosynthetic bacterium Rhodopseudomonas palustris, GJ-22, was previously evaluated for its ability to promote the growth and enhance the immune response of solanaceous plants. In the present study, GJ-22 was shown to significantly repress disease symptom development caused by P. infestans in potato tubers. Curzate (cymoxanil plus mancozeb), a widely used fungicide with high activity against P. infestans, was selected for use in combination with GJ-22. The sensitivity of GJ-22 to the fungicides cymoxanil and mancozeb was tested. The growth of GJ-22 was unaffected by up to 100 mg l−1 cymoxanil or 50 mg l−1 mancozeb in photosynthetic medium. In greenhouse and field experiments, the combined application of GJ-22 and curzate resulted in better disease control than the use of either agent alone. In addition, treatment with 1 × 107 CFU ml−1 GJ-22 plus 700 mg l−1 curzate showed synergistic effects in the field trial. Our results highlight the potential to control potato late blight with the combination of R. palustris strain GJ-22 and curzate, providing environmentally friendly protection with a reduced level of fungicide application.

Genotypic and phenotypic characterization of Phytophthora infestans in South Korea during 2009–2016 reveals clonal reproduction and absence of EU_13_A2 genotype

AbstractIn order to better understand the Phytophthora infestans population structure in South Korea, 172 isolates were collected between 2009 and 2016 from four major potato cultivation areas. Fungicide (metalaxyl and dimethomorph) response, mating type, and microsatellite (SSR) genetic fingerprints were analysed to characterize these isolates. Ten isolates collected in Gyeongnam Province, which specializes in protected winter cultivation in polytunnels, were A2 mating type. All other isolates were A1 mating type. Overall, 42% of the isolates were resistant to metalaxyl, and 43% were sensitive. All isolates were sensitive to dimethomorph. From the SSR fingerprints, 45 distinct genotypes were identified, which could be clustered into four clonal lineages: KR_1_A1, KR_2_A2, SIB‐1, and US‐11. KR_1_A1 was the predominant P. infestans genotype in South Korea. KR_2_A2 was only found in Gyeongnam Province; all isolates were A2 mating type and resistant to metalaxyl. SIB‐1 was dominant until 2013 but its frequency has gradually decreased in more recent years. US‐11 was first found in 2014, after which its frequency has increased to become codominant with KR_1_A1. The calculated standardized index of association (IA) suggests that the South Korean P. infestans population is undergoing clonal reproduction. When compared with populations of P. infestans from the Netherlands, it has less genetic diversity and the dominant Netherlands P. infestans genotype, EU_13_A2 (Blue_13), was not found in South Korea. Such monitoring of the pathogen population contributes to a more efficient integrated pest management‐based control strategy for potato late blight control in South Korea.

In Vitro and In Vivo Effect of Poplar Bud Extracts on Phytophthora infestans: A New Effective Biological Method in Potato Late Blight Control.

The effect of populin extract from black poplar (Populus nigra) on seven different late blight strains was tested under laboratory and field conditions. The growth rate of hyphae was found to be significantly lower in vitro after 3 and 4 v/v% populin applications. Stain M16 was resistant to populin treatment under lab conditions, however. Both 5% and 10% concentration populin reduced the M16 strain’s severity on potato leaves under field conditions and proved to be even more effective than conventionally used fungicides Infinito 687 Sc and Valis M. Higher infection intensity at the 1% level was observed after 24 h using Valis M, and the same trend toward 10% infection remained after 48 and 72 h as well. Low, almost-no-infection intensity was detected after populin 5% and 10% treatment under an open field condition. Altogether, it can be concluded that populin extract can be a low-cost option for growers and an environmentally friendly approach in late blight control.

Field application of Bacillus subtilis isolates for controlling late blight disease of potato caused by Phytophthora infestans

Abstract Field studies on the biocontrol activity of four B. subtilis isolates viz., B. subtilis MTCC-2422 (T-3), B. subtilis KU936344 (T-4), B. subtilis KU936345(T-5) and B. subtilis KU936341 (T-6), against late blight disease of potato caused by fungus like-organism Phytophthora infestans were investigated. These isolates produce mycotoxins against the causal organism. The fungicide (Mancozeb) M 45 (CURZATE®) was used as positive control. Potato (Solanum tuberosum) cultivar, Kufri Jyoti was used. The treatments were utilized as soil drenching as well as foliar spray. Results reveal that, bacterial treatments significantly reduced disease incidence of late blight compared with the control. Bacterial treatments increased the plant vegetative parameters like plant height, sprouting, number of leaves, fresh weight and dry weight of plants. In addition, treatments also showed the clear difference between commercial and non-commercial tuber yield/hectare. In this experiment, two observations displayed the reduction of the disease severity. There was 32.73% increase in the control plot and 14.3% in chemical fungicide, while in bacterial treatments there was 12.75%, 14.09%, 4.7% and 4.13% increase in the T3, T4, T5 and T6, respectively. Soil drenching of bacterial culture gave the high yield in commercial potato tubers, even when compared with the chemical fungicide. The total yield of control block was 166.04 quintals/hectare but non-commercial yield was 101.07 quintals/hectare. In chemical fungicide, total yield was 188.8 quintals/hectare and non-commercial tubers was 69.66 quintals. The bacterial treatments T4, T5, T6, showed less non-commercial potato yield 48.29, 22.60 and 24.67 quintals/hectare in the total yield of 177.02, 212.89 and 190.737 quintals/hectare in respective treatments. So this study uncovers that B. subtilis treatments are effective under field condition for the control of potato late blight.

Analysing social-ecological interactions in disease control: An agent-based model on farmers’ decision making and potato late blight dynamics

In this paper we focus on potato late blight control in the Netherlands to analyse the social-ecological interactions between farmer behaviour and disease dynamics. An agent-based model was developed to analyse the use of crop resistance for sustainable disease control. The framework on farmers’ decision-making was based on a behavioural theory and supported by data from literature and interviews with Dutch potato farmers. This framework was integrated with a previously developed spatially explicit model on potato late blight dynamics. We assumed a scenario where a new resistant potato variety was introduced to the market. The model reproduced a boom-and-bust cycle: the percentage of farmers growing the resistant variety increased until resistance breakdown occurred by emergence and spread of a virulent strain, and in response farmers switched to other potato varieties and management strategies. Several factors and processes were identified that could contribute to the development of sustainable disease management strategies.

Moving perceptions on potato late blight control: Workshops with model-based scenarios

Late blight caused by Phytophthora infestans is one of the main diseases in potato production. The Netherlands has a high potato density and favourable weather conditions for the disease, and this combination leads to frequent outbreaks of late blight. A spatially explicit agent-based model of the host-pathogen system was used in workshops with conventional and organic farmers to demonstrate and discuss the potential role of resistant varieties for effective and sustainable control of late blight. We presented model-based scenarios and used qualitative and quantitative measures to analyse the effect of the workshop on farmers' perception on late blight control. The scenarios simulated effects of farmer decisions regarding the use of crop resistance and fungicide application on disease control at the landscape level over a period of ten years. The model showed that growing a resistant variety (with a single resistance gene) can reduce disease incidence in the landscape, however, after a couple of years resistance breakdown occurs by emergence of a new virulent P. infestans strain. If no countermeasures were taken the new virulent population could spread fast through the landscape, reducing potato yield of resistant fields. The model showed a number of resistance management strategies that could be effective to increase resistance durability. Differences in farmer perception were observed before and after the workshop as well as between conventional and organic farmers. By analysing the disease dynamics at the landscape level, the model showed the importance of collective action. To prevent emergence and spread of a virulent strain it is important to keep disease pressure low. To achieve this, all farmers have to cooperate. During the workshops farmers exchanged views and negotiated possible solutions. We conclude that the use of model-based scenarios in workshops was very useful to increase farmers' knowledge of the system and served as a good starting point for discussions among actors facing the complex problems of late blight control and potato resistance management.

农药组合防治马铃薯晚疫病试验研究

农药组合防治马铃薯晚疫病试验研究