New Strategies for Management of Vegetable Diseases in Organic and Traditional Farms

New Strategies for Management of Vegetable Diseases in Organic and Traditional Farms

Summary

Phytophthora blight, caused by Phytophthora capsici, is a serious threat to production of cucurbits and peppers in the United States (US), as well as in the world. The pathogen attacks crops at all growth stages, causing up to 100% crops losses. Integrated disease management approaches developed in this study can effectively minimize crop losses of cucurbits and peppers caused P. capsici. An integrated practice of seed-treatment, disking the localized infected areas in the field, and fungicide sprays are very effective in controlling Phytophthora blight in cucurbit fields. Planting resistant varieties and/or application of fungicides can effectively control Phytophthora blight in pepper fields. Red-light treatment is very effective for controlling Phytophthora blight of vegetables in greenhouse.

Objectives/Performance Targets

Objective 1: Evaluate the effectiveness of plant resistance induced by red-light treatment for control of Phytophthora blight and other diseases in pumpkin, watermelon, and pepper.

Objective 2: Determine the effects of calcium on the incidence and severity of Phytophthora blight and other diseases in pumpkin, watermelon, and pepper by soil application of CaSO4 and foliar application of CaCl2.

Objective 3: Determine the efficacy of a new copper compound (Cuprofix Disperss) on controlling Phytophthora blight and other diseases in pumpkin, watermelon, and pepper.

Objective 4: Determine the effectiveness of seed-treatment for control of seedling death caused by P. capsici in cucurbit crops.

Objective 5: Determine the effectiveness of integrated approaches of red-light treatment, calcium application, cooper spray, and seed-treatment on controlling Phytophthora blight and other diseases in vegetable farms.

Accomplishments/Milestones

The effect of red-light treatment on the subsequent occurrence of seedling infection of bell pepper, pumpkin, and tomato caused by Phytophthora capsici was investigated in the greenhouse. Red-light treatment is very effective in controlling Phytophthora blight in the greenhouses, but its effectiveness in the fields is not consistent.

The copper sulfate fungicide, Cuprofix Disperss, was tested alone and in combination with other fungicides in laboratory and fields. Cuprofix Disperss suppressed growth and spore germination of P. capsici in the laboratory. Incidence and severity of Phytophthora blight and fruit rot in the plots received Cuprofix Disperss plus fungicide dimethomorph (Acrobat 50WP) or fungicides famoxadone-cymoxanil (Tanos 5050DWG) were significantly lower than those of control plots.

Seed treatment with mefenoxam (0.64 fl oz Apron XL LS/ 100 lb seed) controlled seedling death of processing pumpkins and watermelon, caused by P. capsici, until 5 weeks after sowing seeds.

Seed-treatment plus fungicide spray applications significantly reduced incidence and severity of Phytophthora blight in the fields. In experimental plots, seed treatment with Apron XL LS and spry applications of dimethomorph (6.4 oz of Acrobat 50WP/A) plus copper sulfate (2 lb of Cuprofix Disperss 36.9DF/A) alternated with famoxadone-cymoxanil (10 oz of Tanos 50DWG/A) plus Cuprofix Disperss or copper hydroxide (2 lb of Kocide-2000/A) reduced vine and fruit infection to less than 10% compared to the control plots with 18 and 26% vine and fruit infection, respectively. New phosphorous acid-based compounds (ProPhyt, AgriFos, and Phostrol) were also found effective in controlling Phytophthora blight of cucurbits in the field.

In a field trial of peppers, cultivars Alliance, Aristotle, Enza 9006, Paladin, and Revolution were found resistant to Phytophthora blight. The final stand of asymptomatic plants in the field ranged from 7% for susceptible cultivar (California Wonder) to 70% to the most resistant cultivar Paladin. In another pepper trial, applications of fungicide Ranman (cyazofamid) alone or in combination with fungicide Omega (fluazinam), Acrobat, or Tanos effectively controlled Phytophthora blight. At the end of the season, only 10% of plants in untreated control plots survived. Whereas, 70 to 87.50% of plants in fungicide-treated plots did not exhibit Phytophthora blight symptoms.

Impacts and Contributions/Outcomes

Commercial cucurbit and paper growers in the United States, Canada, Mexico, and other parts of the world have implemented the methods developed in this research and improved crop production. For example, production of processing pumpkins in Illinois has increased by more than 50% in 2005 compared to that of 2000, due to a large extend to effective control of Phytophthora blight.