Production of Conidia of Alternaria cassiae with Alginate Pellets

Formulations of alginate-encapsulated mycelia are used to generate spores for mycoherhicidal application to weed-infested fields and for bulk production of spore-based products. Spore yield of such formulations is a primary determinant of product efficacy. A number of parameters of the alginate process were studied to develop an optimal alginate formulation for field application of Alternaria cassiae, a mycoherbicide for sicklepod (Cassia obtusifolia). The composition of the fermentation medium and of the filler used in formulation and the fermentation time were important variables. The addition of nutrients to the mycelial homogenate after fermentation increased sporulation but the amount and ratio of nutrients in the fermentation medium had a greater influence on spore yield from pellets. Optimal sporulation resulted from mycelia produced during a 60to 70-h fermentation in 2.4% dehydrated potato dextrose broth and 14% V-S vegetable juice and entrapped in pellets containing corn cob grits as the filler.