Biocontrol agent, biofumigation, and grafting with resistant rootstock suppress soil-borne disease and improve yield of tomato in West Virginia

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 than 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 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.