Abstract
Organic tomato growers in West Virginia and neighboring states suffer serious economic losses each year due to soil-borne wilt diseases caused by fungal pathogens including Verticillium dahliae. This study determined the efficacies of biological control agents (BCAs – Serenade SOIL and Prestop), bio-fumigants and transplants grafted to a resistant rootstock in suppressing wilt disease in heirloom tomato cv. Mortgage Lifter in a certified organic production system in West Virginia in two consecutive years. Prestop and Serenade treatments resulted in higher seedling vigor at the early stage. However, within 40 days of field set in the fungal pathogen infested soil, grafted transplants (on resistant rootstock Maxifort) had the highest vigor followed by BCA treatments, biofumigation with mustard cover crop and mustard meal and was lowest in nontreated control. All treatments showed significantly lower Verticillium wilt severity index than control except mustard cover crop and Prestop in 2015 and 2016, respectively. Total fruit harvested over a six-week period indicated that yield from all but mustard cover crop treatment were significantly (P < 0.001) higher compared to the nontreated control in 2015. However, results from 2016 indicated that mustard cover crop would work best for both disease suppression and yield enhancement when tissues were well macerated and incorporated immediately in the soil and covered with impervious plastic for up to 10 days. In 2016, all treatments except Prestop produced higher tomato yield than the nontreated control. In general, yield advantage over nontreated were in the order of grafted > bio-fumigation > BCA treatments > nontreated check. Between two BCAs, Bacillus subtilis (Serenade) consistently provided better disease suppression and improved yield compared with Gliocladium catenulatum (Prestop) in both years. Grafted plants produced 9.1 and 10.0 kg tomatoes/plant in 2015 and 2016, respectively, compared with only 5.0 kg in nontreated control. Our results suggest that grafted transplants, biofumigation and selected BCA should be useful for sustainable management of tomato wilt disease in organic production systems. An economic analysis indicated that grafted tomato can provide the greatest net revenue followed by mustard meal biofumigation in farms infested with wilt causing pathogen.
Highlights
Soil-borne fungal and bacterial pathogen caused vascular wilt dis eases are important plant diseases that limit crop production worldwide (Tjamos and Beckman, 1989)
20 days after seeding, seedlings from treated seeds showed enhanced vigor compared with nontreated, and reduction of Prestop rate from 16 mg/L in 2015 to 1.6 mg/L in 2016 for inoculating planting mix typical v-shaped lesions indicative of Verticillium wilt leaf symptom appeared on the lower leaves
Foliar wilting symptoms occurred on approximately 50% of the plants in the mustard cover crop, Prestop and nontreated control treatments during the middle of hot and dry summer days, plants usually recovered by early the morning
Summary
Soil-borne fungal and bacterial pathogen caused vascular wilt dis eases are important plant diseases that limit crop production worldwide (Tjamos and Beckman, 1989). Verticillium wilt, a major soil-borne dis ease causes significant crop losses in tomato production in many coun tries and states, including West Virginia (WV). We identified the problem of soil-borne fungal pathogens in wilted tomatoes collected from farmers’ fields followed by isolation and analyses of the causal agents at the West Virginia University (WVU) Plant Diagnostic Clinic. General recommendations for managing soil-borne pathogens are to rotate fields and use resistant varieties. ‘Mortgage Lifter’) and unavailability of suitable land areas to rotate warrants developing a multi-tactics-based integrated pest management (IPM) method for bio rational management of these notorious soil-borne pathogens.
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