Viability and stability of biological control agents on cotton and snap bean seeds

Cotton and snap bean were selected for a multi-year, multi-state regional ( south-eastern USA) research project to evaluate the efficacy of both commer cial and experimental bacterial and fungal biological control agents for th e management of damping-off diseases. The goal for this portion of the proj ect was to determine the viability and stability of biological agents after application to seed. The biological seed treatments used included: (1) Bac illaceae bacteria, (2) non-Bacillaceae bacteria, (3) the fungus Trichoderma and (4) the fungus Beauveria bassiana. Seed assays were conducted to evalu ate the following application factors: short-term (less than or equal to3 m onths) stability after seed treatment; quality (ie isolate purity); compati bility with chemical pesticides and other biocontrol agents; application un iformity between years and plant species. For the bacterial treatments, the Bacillaceae genera (Bacillus and Paenibacillus) maintained the greatest po pulation of bacteria per seed, the best viability over time and the best ap plication uniformity across years and seed type. The non-Bacillaceae genera Burkholderia and Pseudomonas had the least viability and uniformity. Altho ugh Beauveria bassiana was only evaluated one year, the seed fungal populat ions were high and uniform. The seed fungal populations and uniformity for the Trichoderma isolates were more variable, except for the commercial prod uct T-22. However, this product was contaminated with a Streptomyces isolat e in both the years that it was evaluated. The study demonstrated that Baci llaceae can be mixed with Trichoderma isolates or with numerous pesticides to provide an integrated pest control/growth enhancement package. (C) 2001 Society of Chemical Industry.