Phytophthora infestans is the causal organism of potato late blight, the most important disease in potato, the second most important arable crop in Europe. The P. infestans population in Europe is well known for its sudden changes in composition. Currently it is composed of a wide variety of genotypes, some of which are dominant clonal lines while others are rare or even unique to a year or location. Fungicides play a crucial role in the integrated control of late blight. Since its introduction in the Netherlands in 1992, fluazinam has been used in late blight control strategies in ware and starch potatoes. It has a broad spectrum of activity and is effective against a range of diseases including potato late blight. Fluazinam interrupts the pathogen cell's energy production process by an uncoupling effect on oxidative phosphorylation. It is considered to have a low resistance risk. Until recently, reduced efficacy against fluazinam was not detected in P. infestans surveys in Europe. In this paper we present the finding of a new clonal lineage (EU_33_A2) of P. infestans in the Netherlands and the reduced efficacy of fluazinam to control one of the EU_33_A2 isolates in field experiments carried out in 2011 and 2015 under high disease pressure. The potential effects of this finding on practical late blight control strategies are discussed.

Indonesia is the largest potato producer in Southeast Asia. Late blight (Phythophtora infestans) is one of the most important diseases especially in the rainy season. Therefore, farmers frequently spray fungicides to prevent infection. Forty farmers in West Java were trained in implementing good agricultural practices. To assess the impact of the training, late blight control strategies at the trainees' fields were recorded. The baseline registration in the dry season of 2013 revealed that on average 16.6 times fungicides were applied. The average spray volume was 919 L ha(-1), whereas the recommended spray volume ranges from 400 to 600 L ha(-1) depending on the crop stage. Many farmers added an adjuvant to the spray mixture to increase the rainfastness of the fungicides. The fungicide costs ranged from 11.4 to 14.7% of the total production costs. The second registration, wet season of 2013/2014, showed a similar number of applications as in the dry season but the fungicide input was clearly higher due to a higher spray volume of 1,052 L ha(-1) and more fungicides per application which caused higher fungicide costs ranging from 4 to 35% of the total production costs. Parallel and supportive to the trainings, three late blight demos were implemented in wet seasons. In the first demo (2013/2014), more recently registered fungicides controlled late blight similarly compared to the fungicide mixture often used by farmers, but they were 10-15% more expensive. In the second (2014/2015) and third demo (2015/2016), again the more recently registered fungicides did not perform better and were more expensive. A 20% reduction in spray volume had a similar effect on late blight control as the farmers' practice using high volumes. At reduced spray volumes, the use of an adjuvant did increase late blight control. It is estimated that the spray volume can be reduced with 10-20% without loss of efficacy and thus save costs.

Since 2013 the Netherlands Ministries of Economic and Foreign Affairs has been involved in private companies in research and development (R&D) in developing countries. This in a policy going “from aid to trade”. Especially in upcoming markets, R&D is carried out through Public Private Partnerships. Such partnerships not only include R&D organizations in the two countries but specifically also include businesses in both countries. This was to assure a logical flow of material and knowledge by all parties involved. Half of an R&D project is funded by the ministry and the rest is covered by a consortium of companies that contribute in kind and in cash. The policy is aimed at stimulating business development in developing countries and the Netherlands through cooperation and joint R&D. The paper explains how eleven consortia around potato business opportunities were formed, their R&D need was elicited and R&D projects formulated in the Asian countries China, India, Indonesia, Vietnam, Bangladesh and Myanmar, and Ethiopia and Kenya in Africa. In common are fact finding and descriptions of cropping systems, yield gap analysis and value chains in each country. Emphases differ with China looking for an integrated system of field operations, India for optimization of storage and processing, Indonesia to reduce pesticide and nutrient inputs, Vietnam for widening the varietal base, Bangladesh for combating late blight, Myanmar for cultural practices that lead to increased yield, Ethiopia where a potato processing unit is being established and Kenya importing seed potato from the Netherlands. Some content information is given as examples to illustrate the approach and some preliminary conclusion are discussed.

As part of the vegIMPACT project a laboratory test in the Netherlands was done with potato (Solanum tuberosum) var. Bintje and onion (Allium cepa) var. Sturon. In both crops mancozeb was sprayed with and without the adjuvants Bond and Indostick. In both crops these three treatments were applied with high and low spray volumes. After spraying, rain was simulated (0.5, 3 or 6 hours after spraying and a control without rain) to test the sticker properties. After five days, plant leaves were analysed on mancozeb residue. Five days after spraying the potato plants were inoculated with Phytophthora infestans and onions with Peronospora destructor. Subsequently, disease symptoms were observed and visually rated as percentage of infected leaves. In potato lower mancozeb residue levels were measured at high spray volumes. Under dry conditions the effect of adjuvant on mancozeb residue in potato was limited. In onion the spreader characteristics of the adjuvants resulted in higher mancozeb residue concentrations than without adjuvant. The impact of rain simulation was much bigger than the impact of adjuvant on mancozeb residue and late blight incidence. Therefore, it is not recommended to spray when rain is expected within the same day as spraying. With rain simulation in both onion and potato more mancozeb residue was present when using the adjuvant Bond than when spraying mancozeb without an adjuvant. However, also with Bond after rain simulation high amounts of mancozeb were washed off. Mancozeb with Bond in potato resulted in less late blight incidence than with spraying mancozeb without adjuvants. Overall the adjuvant Bond performed better than Indostick in terms of mancozeb retention on both potato and onion leaves . Indostick had good spreading properties that under dry conditions resulted in higher mancozeb residue levels in onion. Under rainy conditions the effect of Indostick on mancozeb residues was not or only slightly better than mancozeb without adjuvant.

Initial sources of inoculum of Phytophthora infestans were investigated in ten potato fields with early outbreaks of potato late blight. Infected plant samples and isolates from these fields were examined with respect to mating type prevalence, fungicide resistance and genotypes based on microsatellites A high proportion (91 %) of the isolates recovered were of mating type A1. However, both mating types were found in 3 of 9 fields with more than one isolate recovered, and sometimes both mating types were found on the same plant. Most of the isolates recovered from fields treated with metalaxyl-M prior to sampling had reduced sensitivity or were resistant to metalaxyl-M, and most of the isolates recovered form fields without metalaxyl treatment were sensitive. The isolates recovered from fields treated with propamocarb prior to sampling had a higher frequency of reduced sensitivity to propamocarb than isolates from fields without propamocarb treatment. We found that most plants contained more than one P. infestans SSRgenotype. Clustering analysis of the infected samples revealed that most samples clustered together according to fields. By combining information from P. infestans isolates and DNA extracts from the leaf lesions we found examples of both mating type A1 and A2 having the same multilocus genotype. This result indicates that both of these genotypes have a common ancestor, hence the inoculum originates from oospores. Although this a minor study of only 10 fields with a limited amount of isolates and plant samples, the results indicate oospores in the soil is an inoculum source. Hence the forecasting model to predict outbreaks of potato late blight should be modified to include this.

De doelstelling van het rapportage-project was: - Op basis van bestaande kennis uit binnen- en buitenland (metingen, modelstudies) inzichtelijk maken in hoeverre oppervlakkige afspoeling van (vrijwel) vlakke percelen verantwoordelijk kan zijn voor (piek) belasting van oppervlaktewater; - Inzichtelijk maken in hoeverre een vergelijking met andere emissieroutes mogelijk is en, zo mogelijk, deze vergelijking inzichtelijk maken; - Verkenning van de mate van overeenstemming tussen de uitgangspunten van de modelmatige berekening van afspoeling en de situatie op representatieve praktijksituaties in Nederland. Wanneer relevante afwijkingen verwacht worden, deze benoemen; - Vaststellen of er zicht is op effectieve maatregelen om oppervlakkige afspoeling tegen te gaan. Dit kunnen bestaande of nieuwe maatregelen zijn. Hiervoor is een korte internationale literatuurscan uitgevoerd naast een verkenning om te bepalen hoe vaak afspoeling van water kan optreden op landbouwgronden in het vlakke deel van Nederland. Voor dit laatste onderdeel zijn neerslaggegevens van 30 jaar geanalyseerd op de frequentie van optreden van buien voor 3 meteostations en zijn zand- en kleigronden gekarakteriseerd met hun infiltratiesnelheid.

Field experiments were carried out in Denmark, United Kingdom and the Netherlands in 2009, 2010 and 2011. Thus nine experiments were carried out to compare the effectiveness against tuber blight by measuring the protection of leaves and tubers against infection by late blight caused by application of a fungicide in a standard 7-day spray schedule. This report describes the analysis of the efficacy of fungicides to control potato tuber blight during the second part of the season. A tuber blight rating was established for five fungicides.

De P. infestans-populatie wordt steeds agressiever, de cyclus wordt korter en er kan een snellere uitbreiding van de epidemie optreden als niet wordt ingegrepen. Bestrijding van Phytophthora in de teelt van aardappelen vraagt daardoor steeds meer aandacht. Het ontwikkelen van strategieen die zowel rekening houden met doseringsverlaging, rasresistentie, gecombineerde bestrijding Alternaria en Phytophthora, milieu en kosten vindt over meerdere jaren in veldproeven plaats op verschillende locaties in Nederland met verschillende teeltomstandigheden en verschillende klimatologische omstandigheden. Ieder jaar zijn er enkele aanpassingen in proefopzet, gebaseerd op de nieuwste inzichten uit Phytophthora onderzoek (Parapluplan Phytophthora). Het onderzoek werd uitgevoerd in opdracht van het Ministerie van Landbouw.

Phytophthora infestans, the causal agent of late blight, is a major threat to potato production in northwestern Europe. Before 1980, the worldwide population of P. infestans outside Mexico appeared to be asexual and to consist of a single clonal lineage of A1 mating type characterized by a single genotype. It is widely believed that new strains migrated into Europe in 1976 and that this led to subsequent population changes including the introduction of the A2 mating type. The population characteristics of recently collected isolates in NW Europe show a diverse population including both mating types, sexual reproduction and oospores, although differences are observed between regions. Although it is difficult to find direct evidence that new strains are more aggressive, there are several indications from experiments and field epidemics that the aggressiveness of P. infestans has increased in the past 20 years. The relative importance of the different primary inoculum sources and specific measures for reducing their role, such as covering dumps with plastic and preventing seed tubers from becoming infected, is described for the different regions. In NW Europe, varieties with greater resistance tend not to be grown on a large scale. From the grower's perspective, the savings in fungicide input that can be achieved with these varieties are not compensated by the higher (perceived) risk of blight. Fungicides play a crucial role in the integrated control of late blight. The spray strategies in NW Europe and a table of the specific attributes of the most important fungicides in Europe are presented. The development and use of decision support systems (DSSs) in NW Europe are described. In The Netherlands, it is estimated that almost 40% of potato growers use recommendations based on commercially available DSS. In the Nordic countries, a new DSS concept with a fixed 7-day spray interval and a variable dose rate is being tested. In the UK, commercially available DSSs are used for c. 8% of the area. The validity of Smith Periods for the new population of P. infestans in the UK is currently being evaluated.

Tot eind juli 2010 waren er, dankzij het aanhoudende zomerse weer, maar een paar infectiekansen voor Phytophthora. Daarna waren er, afhankelijk van de regio, meerdere kritieke perioden. Tot eind juli kon het aantal Phytophthora-bespuitingen beperkt blijven en de dosering kon vaak verlaagd worden zonder nadelige gevolgen. Hiermee kon flink op middelkosten bespaard worden in vergelijking met een wekelijks spuitschema met 100% dosering. Bij de recente hoge infectiedruk in de eerste weken van augustus gaven de waarschuwingssystemen vanzelfsprekend stringentere spuitadviezen, afhankelijk van de plaatselijke situatie. Op proeven bij drie proefboerderijen (Vredepeel, Westmaas en Kollumerwaard) worden verschillende modules van waarschuwingssystemen getest. In Vredepeel is aan het einde van het groeiseizoen toch Phytophthora in verschillende proefobjecten waargenomen. In Munnekezijl zijn in een paar proefobjecten slechts enkele aangetaste blaadjes gevonden, terwijl in Westmaas nog geen enkele aantasting in de proef is waargenomen. In objecten waar veel op fungiciden bespaard is, werd niet meer aantasting waargenomen dan in objecten met een hoger fungicidengebruik.