2004 Annual Report for LNC03-228
New Strategies for Management of Vegetable Diseases in Organic and Traditional Farms
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, copper spray, and seed-treatment on controlling Phytophthora blight and other diseases on 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. Seedlings were inoculated with P. capsici zoospores (adding 2 ml of spore suspension onto soil around seedling) or transplanted into pots filled with artificially infested soil mix. Red-light treatment of seedlings reduced seedling death up to 79%. Only 21 to 36% of red light treated seedlings became infected, whereas 78 to 100% of the control seedlings (grown in natural light or under white light) became infected and died. Red-light treatment of seedlings during nights (12 h per day) for four weeks is the most effective.
Although red-light treatment was effective against P. capsici in the greenhouse, the treatment also delayed the incidence of Phytophthora blight in the field. The treatment alone provided season-long protection for the plants against P. capsici. Further research is underway to determine effectiveness of red-light treatment for control of Phytophthora blight in fields.
The effectiveness of calcium to protect pumpkin and watermelon against Phytophthora blight was tested in a field that was naturally infested with P. capsici. CaCl2 was applied twice (20 lb Ca each time) onto plants. CaSO4 was applied once (800 lb CA) onto the soil and incorporated. The incidence of foliar infection in the plots that received soil and foliar applications of calcium was significantly lower than that of control plots. However, calcium application (soil and/or foliar) alone did not provide satisfactory season-long protection of plants against P. capsici. Also, the incidence of fruit infection in the treated plots with calcium plus copper compound “Cuprofix DF” was significantly lower than that of untreated plots.
The copper sulfate fungicide, Cuprofix Disperss, was tested alone and in combination with other fungicides, with potential effects on P. capsici, in the laboratory and in 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 that received Cuprofix Disperss plus the fungicide dimethomorph (Acrobat 50WP) were significantly lower than blight and fruit rot in control plots.
Seed treatment with mefenoxam (0.64 fl oz Apron XL LS/ 100 lb seed) and metalaxyl (1.5 fl oz Allegiance FL/ 100 lb seed) controlled seedling death of processing pumpkins and watermelon, caused by P. capsici. In greenhouse studies, at inoculum level of 600 cfu/g soil, the average seedling stands 31 days after seeding were 88.3, 85.8, and 45.7% for Apron, Allegiance, and untreated control, respectively. In field trials, the average seedling stands 35 days after seeding were 76.7, 74.7, and 44.9% for Apron, Allegiance, and untreated control, respectively.
Seed-treatment plus fungicide spray in pumpkin, and red-light treatment plus fungicide spray in pepper and tomato significantly reduced incidence and severity of Phytophthora blight in experimental plots of pumpkin and watermelon and commercial field of cucurbits. In experimental plots, under heavy disease pressure, seed treatment with Apron XL LS and spray 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 copper hydroxide (2 lb of Kocide-2000/A) resulted in only 11.7% vine and 9.8% fruit infection, compared to 36.7 and 49.4% vine and fruit infection, respectively, in untreated plots. An integrated management using fungicide seed treatment with Apron XL LS, field scouting and disking areas with localized infected plants, and spray applications of fungicides Acrobat plus copper hydroxide (1.33 pt of Champ 37.5F/A) alternated with Tanos plus Champ, at 7-day intervals, beginning with the first sign of the diseases, reduced yield losses in commercial pumpkin fields to less than 10%, compared to more than 50% yield losses in unsprayed fields.
Impacts and Contributions/Outcomes
Illinois grows about 20,000 acres of pumpkin and 10,000 acres of cucumbers, eggplants, cantaloupe, peppers, squash, tomatoes, and watermelons per year. The North Central region produces more than 130,000 acres of these crops per year. Phytophthora blight, caused by P. capsici, is a serious threat to production of these crops in the region as well as nationwide. The methods that are being developed in this research for control of Phytophthora blight of vegetables are already implemented by commercial pepper and cucurbit growers to manage Phytophthora blight in commercial fields. Red-light treatment to induce resistance and calcium application can be used on organic farms to reduce crop losses to Phytophthora blight. Effective management of Phytophthora blight, developed during this research, has already resulted in expansion of pumpkin and pepper production throughout Illinois. The results of this study has are now used in the United States, Canada, and Mexico.