An improved granular formulation for a mycoherbicidal strain of Fusarium oxysporum

Modifications were investigated to improve shelf-life or long-term survival upon storage of an extruded Oryza sativa L. (rice) flour:gluten:clay: oil formulation (C7) of a mycoherbicide, Fusarium oxysporum Schlechtend: Fr. f sp, erythroxyli strain EN4, that causes vascular wilt in Erythroxylum coca var. coca (coca). Fermenter-produced biomass, which contained abundant desi ccation-resistant chlamydospores, was incorporated into Various adaptations of C7 and stored at room temperature (22 to 25 C) under moderately high (5 0 to 60%) and low (0 to 5%) relative humidities (RHs). The effect of RH on shelf-life was not significant up to 4 mo of storage, while the presence of oil, added to improve its extrusion, reduced viability significantly. Addi tion of Gossypium hirsutum L. (cotton) embryo hour or complete elimination of oil from the formulation improved shelf-life from 3 mo to > 12 mo. Shelf -life was further improved by removing the binding agent gluten in the form ulation and replacing it with autoclaved 0. sativa hour Ability of the form ulations to produce secondary propagules, tested on 1% water agar, indicate d that, while adding oil had no effect, G. hirsutum embryo flour increased desiccation-resistant chlamydospore counts but lowered macroconidial counts . Autoclaved rice hour (MR) significantly improved both macroconidial and m icroconidial counts without affecting chlamydospore counts. None of the for mulations affected the total viable propagule counts. When compared with th e original formulation (C7), the modification (MRRP7), with MR, G. hirsutum embryo hour and without oil, was found to have improved shelf-life at high er temperature and RHs and enhanced potential for secondary chlamydospore f ormation. These characteristics are important for survival of the formulate d F: oxysporum under less expensive storage conditions and, once applied, f or survival in the soil.