Bio-PhytoPRE - ein Warn- und Prognosesystem zur Bekämpfung der Kraut und Knollenfäule im ökologischen Kartoffelanbau in der Schweiz

In organic potato production, copper fungicides are the only mean for an effective direct control of late blight. To avoid negative impacts of copper accumulation in the environment, intensive research is done to develop efficient copper free agents (CFA) and new strategies for disease prevention. However, the search for such CFA and strategies proves to be more difficult than expected. Therefore an abdication of copper products is not yet possible. To approach a copper free organic potato production, the Agroscope FAL Reckenholz is developing the Bio-PhytoPRE decision support system to assist Swiss organic potato producers to control late blight with reduced amounts of copper or CFA

Control of Phytophthora infestans in organic potato production

Phytophthora infestans, the cause of late blight, is the most devastating pathogen in potatoes world-wide. To replace copper fungicides in organic potato production, we examined preparations based on plant extracts, micro-organisms, and other natural compounds for their effect on late blight in field trials as well as in vitro and in vivo. Most of this work we realised as participants of the EU project Blight-MOP. The majority of the preparations effectively inhibited P. infestans in vitro or in vivo on tomato plants. However, under field conditions and with applications once a week, commercial and experimental copper-free preparations failed to sufficiently control late blight. In contrast, copper fungicides applied according to the decision support system Bio-PhytoPRE or in regular intervals consistently reduced foliar blight and prevented significant yield losses. Results from an in vitro test and from a detached leaf test indicate that a main cause of the failure of copper-free preparations could be low stability towards rain or dew

Kraut- und Knollenfäule im Kartoffelanbau - ist im ökologischen Anbau eine wirksame Bekämpfung ohne Kupfer möglich?

In laboratory, growth chamber, micro-plot and small-plot field trials, 53 copper-free preparations (CFPs) were examined for their potential to control potato late blight (PLB) caused by Phytophthora infestans (PI). In-vitro, 43% of the CFP inhibited the germination of sporangia or the mycelial growth of the pathogen completely. In growth chamber trials, 21% of them reduced PI foliar blight of tomato seedlings by at least 80%. In contrast, in small-plot field trials with potatoes under practice like applications, none of the CFPs sufficiently controlled the disease. Even in micro-plot field trials with applications twice a week the efficacies did not exceed 60%. With in-vitro tests we showed that the reason for the insufficient performance of the CFPs was due to their lack of persistence and rainfastness. However, applications of copper fungicides with low rates according to the decision support system Bio-PhytoPRE resulted in a good control of late blight. We recommend using this strategy until CFPs are developed for practise application

Einfluss von Phytophthora infestans auf den Kartoffelertrag in Abhängigkeit von der Nährstoffversorgung und optimierten Kupferapplikationen

Late blight, caused by Phytophthora infestans is commonly thought to be the factor most limiting yield in organic potato production. However, because there is no fully effective fungicide available to control late blight, there are virtually no yield loss data available for organic farming conditions. In large-scale experiments covering 2-6 ha from 2000-2002, late blight assessments were conducted throughout the season in small sections throughout the field. The same sections were harvested, resulting in between 400 and 700 data points per experiment and year. In a second set of experiments, from 2002-2004, the interactive effects of N-availability in the soil, climatic conditions and late blight were studied in the presence and absence of copper fungicides for the mid-early main-crop potato variety Nicola. Again, late blight and yield assessments were conducted within defined sections in the field resulting in about 100 data points per experiment. In 2005 and 2006, new copper products with minimal copper contents (157g Cu/ha and applica-tion) and optimised applications using the model Bio-PhytoPRE were integrated. Depending on year and variety, between 0 and 40% of the variation in yield could be explained through late blight severity. Copper fungicides in most cases did slow down epidemics somewhat adding an average of 3 days to the growth duration. However, only 26% of the variation in yield could be attributed to disease reductions. A multi-variate model including disease reduction, growth duration and temperature sum, and soil mineral N contents for the years 2002-2004 (FINCKH et al., 2006) could explain 61% of the observed variation in yield. However, the model failed when N-supply was extremely high. In 2005-2006, without the forecasting model, copper had no significant effect on dis-ease in plots with low nutrient availability while minimised applications combined with the forecasting model resulted in more reliable disease reductions even under low nutrient conditions. A reduction of the current maximally allowed Copper inputs from 3 kg to 1.5 kg per ha and year should thus be considered. Overall yield gains through copper applications were only 10% on average. The economic usefulness of copper applications needs to be scrutinised before recommending its use. The implications of the results on the management of organic potatoes will be discussed

Fusarium and mycotoxin spectra in Swiss barley are affected by various cropping techniques

Fusarium head blight is one of the most important cereal diseases worldwide. Cereals differ in terms of the main occurring Fusarium species and the infection is influenced by various factors, such as weather and cropping measures. Little is known about Fusarium species in barley in Switzerland, hence harvest samples from growers were collected in 2013 and 2014, along with information on respective cropping factors. The incidence of different Fusarium species was obtained by using a seed health test and mycotoxins were quantified by LC-MS/MS. With these techniques, the most dominant species, F. graminearum, and the most prominent mycotoxin, deoxynivalenol (DON), were identified. Between the three main Swiss cropping systems, Organic, Extenso and Proof of ecological performance, we observed differences with the lowest incidence and toxin accumulation in organically cultivated barley. Hence, we hypothesise that this finding was based on an array of growing techniques within a given cropping system. We observed that barley samples from fields with maize as previous crop had a substantially higher F. graminearum incidence and elevated DON accumulation compared with other previous crops. Furthermore, the use of reduced tillage led to a higher disease incidence and toxin content compared with samples from ploughed fields. Further factors increasing Fusarium infection were high nitrogen fertilisation as well as the application of fungicides and growth regulators. Results from the current study can be used to develop optimised cropping systems that reduce the risks of mycotoxin contamination

Ecological Dynamics and Microbial Treatments against Oomycete Plant Pathogens

In this review, we explore how ecological concepts may help assist with applying microbial biocontrol agents to oomycete pathogens. Oomycetes cause a variety of agricultural diseases, including potato late blight, apple replant diseases, and downy mildew of grapevine, which also can lead to significant economic damage in their respective crops. The use of microbial biocontrol agents is increasingly gaining interest due to pressure from governments and society to reduce chemical plant protection products. The success of a biocontrol agent is dependent on many ecological processes, including the establishment on the host, persistence in the environment, and expression of traits that may be dependent on the microbiome. This review examines recent literature and trends in research that incorporate ecological aspects, especially microbiome, host, and environmental interactions, into biological control development and applications. We explore ecological factors that may influence microbial biocontrol agents’ efficacy and discuss key research avenues forward

FusaProg: risk assessment of fusarium and mycotoxin infestation in wheat production

FusaProg and FusaProg Light are prognosis models in conventional wheat production to assess the risk of infection by fusarium and mycotoxins in Switzerland. FusaProg Light is freely accessible and offers the farmer a quick risk assessment for day to day weather conditions. FusaProg is an extended version, only for registered users, with a tailor-made risk assessment and detailed prognosis evaluation for local conditions. FusaProg offers downloadable data and maps on the infection risk and mycotoxin (DON) forecast for registered wheat crops in Switzerland related to weather conditions. The optimization of the wheat cultivation systems and extension by the model helps to avoid the overuse of toxins in conventional farming. Organic farmers may use the prognosis model to decide whether intervention of organic agents are needed. Data on infection risk per variety is provided for the user

Botanicals and Phosphonate Show Potential to Replace Copper for Control of Potato Late Blight

Potato late blight (PLB) caused by Phytophthora infestans (Pi) is the most harmful disease in potato production worldwide. In organic farming, copper is used despite its persistence in soil and toxicity to soil organisms. To replace copper, suspensions of powders from three promising botanicals, including bark of buckthorn (Frangula alnus, FA), roots of medicinal rhubarb (Rheum palmatum) and galls of the nutgall tree (Galla chinensis), were tested in multi-year field experiments. The current study shows for the first time that botanicals could replace copper under field conditions and best PLB reduction on leaves was achieved with FA, reaching a level close to that of 2 to 3 kg copper per hectare and year. Better results than with copper were achieved with Phosfik® (Ph), a phosphonate-based product. For both FA and Ph, the mode of action is based on induced resistance, for Ph also on direct fungicidal effects. A disadvantage of Ph is the accumulation of residues in potato tubers. Nevertheless, two to three applications with 2 to 3 L/ha of Ph would be feasible to not exceed a minimal risk level (MLR) of 20 mg/kg of phosphorous acid as proposed by the European Food Safety Authority. Due to an excellent environmental profile and a complex mode of action counteracting Pi resistance, phosphonate-based products would be most suitable for sustainable PLB management in integrated pest management (IPM) programmes

Why farmers deviate from recommended pesticide timing: The role of uncertainty and information

BACKGROUND Precise timing of pesticide applications, as recommended by decision support systems, can ensure crop protection, while maintaining efficient use of pesticides. Yet, farmers often deviate from recommended timing strategies. Here, we assess and explain farmers’ choices to follow or not follow recommendations for the timing of fungicide applications against potato late blight in Switzerland. RESULTS Based on daily fungicide application records as well as regional application recommendations and disease pressure we found that 36% of applications take place earlier than recommended. Using regression analysis, we identified the exposure to economic risks of infection, susceptibility of the planted potato varieties to late blight infections, as well as yearly differences in disease occurrence as the most important determinants of farmers’ application decision. CONCLUSIONS Our results indicate that decisions to not follow application recommendations and apply early are linked to available information and uncertainty with respect to disease predictions. Based on our results, we make recommendations on how to account for farmers’ uncertainty with regard to the timing of pesticide applications in the design of pesticide policies and agricultural decision support systems. These include the use of new technologies and data, mandatory reporting and tailor made taxes and insurance solutions. Although the focus of this article is on late blight in Switzerland, our analysis can easily be extended to other countries and important plant diseases like powdery mildew in grapevines or Fusarium head blight in winter wheat.ISSN:1526-498XISSN:1526-499

Low-Cost Spore Traps: An Efficient Tool to Manage Fusarium Head Blight through Improved Cropping Systems

Fusarium head blight (FHB) is a devastating disease of wheat. Worldwide, Fusarium graminearum is the most dominant FHB-causing species. Its most common toxin, deoxynivalenol (DON), impairs food and feed safety and has an enormous economic impact. Agronomic factors such as crop rotation, soil management and host genotype strongly influence the occurrence of F. graminearum. Infected plant debris from previous crops, on which perithecia and ascospores develop, represent the main source for FHB, and hence, improved cropping systems aim to reduce this inoculum to decrease the infection risk. The best measure to evaluate the disease pressure is spore traps that detect deposited airborne ascospores. Commercial spore traps are expensive and require power sources, thus, they are not suitable for investigations in field experiments with different treatments. In consequence, we developed spore traps containing a Petri dish with Fusarium-selective agar, protected by aluminum dishes and attached on a wooden board. We compared the data of our low-cost trap with those of a commercial high-throughput jet sampler and obtained equivalent results. In field experiments to compare cropping systems, we observed a high correlation between the DON content in wheat grains and the number of colonies from deposited spores. Our spore trap proved to be a highly valuable tool to not only study FHB epidemiology but also to identify innovative cropping systems with a lower risk for FHB and DON contamination