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

Phosphonat zur Bekämpfung der Phytophthora infestans bei Kartoffeln – eine mögliche Alternative zu Kupfer?

Since more than hundred years, copper-products are used to control late blight of potato, caused by Phytophthora infestans. However, the heavy metal copper accumulates in the soil and affects soil flora and fauna. For this reason, copper agents are listed in the EU only until the end of November 2016. In conventional and integrated farming, copper products have been replaced by synthetic fungicides. In organic production, intensive research is conducted to develop effective alternatives that could replace copper fungicides. In Germany, plant strengthening agents based on phosphonate are allowed to be used in organic viticulture until the end of the flowering period to control downy mildew. However, if vine plants are treated with phosphonate after flowering, residues remain in the grapes. Nevertheless, the use of these products in viticulture enabled a reduction in copper treatments. Potato field trials were conducted in order to investigate whether phosphonate products can entirely or partially replace copper fungicides. Another aim was to clarify to what extent residues can be reduced with applications limited to a particular time or growth stage period

Regulierung der Kraut- und Knollenfäule der Kartoffel mit Faulbaumrinde

In indoor trials with potted potato plants and in micro- and small plot field trials, prepa-rations of Frangula alnus controlled Phytophthora infestans leaf blight significantly bet-ter than other antifungal plant preparations and the copper free reference Mycosin®. However, under field conditions the efficacy of the buckthorn bark preparation (BBP) was drastically lower than in the indoor trials. Therefore and in order to avoid environ-mental pollution with solvent of the plant extract, we developed a procedure to apply finely ground plant material as suspension directly on the potato plants without any ex-traction. The efficacy of BBP applied as suspension was significantly higher than those of ethanolic extracts. To improve the weather stability or the rainfastness, BBP suspensions were amended with wood protection oils in a model trial to demonstrate the effect of a good formulation. The efficacy of these formulations proved to be as ef-ficient as copper with a dosage of 200 g ha-1 per treatment. This was also the case for a BBP with the additive Nu-Film® in a small plot field trial at Zürich-Reckenholz. How-ever, in this trial the disease pressure was low

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

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

Bekämpfung des Schneeschimmels (Microdochium majus) bei Winterweizen mit Naturstoffen – vom Labor ins Feld

The fungal pathogen Microdochium majus, causing snow mould, seedling blight or foot rot results in severe yield losses in small grain cereals. There are few options to control this pathogen in organic production. In this study, aqueous extracts and powders from the botanicals chamomile, meadowsweet, thyme and Chinese galls were tested in vitro against M. majus conidia germination and mycelial growth. Subsequently, powders of three chosen botanicals were tested for their effect on emergence of M. majus infected wheat seedlings from soil in climate chambers. Furthermore, seed treatments with warm water, a commercialised bacterial product and one chosen botanical were tested in a field experiment throughout three consecutive years. Of the botanicals tested, Chinese galls showed the highest efficacy in controlling M. majus, reducing conidia germination and mycelial growth by up to 97 and 100 %, respectively. In the growth chamber, an application with Chinese galls compared with the control treatment increased total seedling emergence by up to 57 %. In the field, yield increase through Chinese galls, the bacterial product and the warm water treatment compared with the control was 19, 10 and 37 %, respectively. This study demonstrated the potential of Chinese galls to control M. majus in wheat

Bekämpfung von Fusarien mit antifungalen Pflanzenprodukten und deren Effekte auf den Mykotoxin-Gehalt von Weizen

Fusarium graminearum (FG) is the most prevalent Fusarium Head Blight (FHB) fungus in Switzerland. In conventional agriculture, fungicides are used to reduce the risk of FHB infection and mycotoxin contamination of wheat. As an alternative for organic wheat production, we examined plant-based products that showed antifungal effects from our previous late blight field trials. In bioassays, the effect of these antifungal plant preparations (APP) was screened against FG. In 2006 and 2008, the most active APP, Rheum palmatum, Frangula alnus and preparations of Galla chinensis as well as a plant substance (PSX), were used as FHB control agents in field trials with artificial FG infections. In both years, FG incidence and deoxynivalenol content were significantly reduced by the APP. In 2006, the reduction was in the same dimension as applications with Pronto Plus®, a fungicide mixture of tebuconazole and spiroxamine

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

Bekämpfung von Microdochium nivale (Schneeschimmel) auf Weizen mit Präparaten auf Pflanzenbasis

Snow mold, caused by the fungal pathogen Microdochium nivale, is an important seed-borne disease of various cereals and fodder plants, leading to reduced stands after emergence. No agricultural measures are known to prevent snow mold, hence, direct control measures are needed. For organic agriculture, seed dressing with plantbased products could be an alternative. In contrast to spray treatments onto the crop, the formulation and application of plant preparations onto seeds represents a greater challenge in terms of adhesion, persistence, and lasting efficacy. In the current study, three plant-based powders applied with two different seed coating materials were tested for their efficacy against MN of wheat. Both adjuvants demonstrated equally satisfying adhesion and showed no differences in terms of disease control. One of the plant-based preparations reduced in vitro the MN infestation of a naturally infected seed lot by 50%, whereas in vivo, it increased emergence of wheat seedlings by 71%

Medicinal plants in late blight management of organic potato

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