Preparation of stable, granular formulations containing Fusarium oxysporum pathogenic to narcotic plants

Biomass of formae speciales of Fusarium oxysporum pathogenic to the narcotic plants coca (Erythroxylum coca) and opium poppy (Papaver somniferum) was incorporated into wheat flour-kaolin granules (Pesta). Shelf life (inoculum viability) of samples with the coca pathogen (strain EN4-S; 2.6 x 10(7) colony-forming units (cfu)/g, mostly chlamydospores) was at least 1 year at 35 degrees C when stored at a water activity (a(W)) of 0.12 (equal to 12% relative humidity) and 2 years when stored at 25 degrees C. Shelf life of samples with the poppy pathogen (strain CP3A; 3.4 x 10(7) cfu/g, mostly microconidia) was about 10 months at 33 degrees C and 0.33 a(W). Shelf life was maximized by optimizing water activity (near 0.12 am for F. oxysporum) and incorporating at least 5 x 10(6) cfu/g of chlamydospore inoculum. Multikilogram quantities of granular formulations were produced by scaling up the production process by using twin-screw extrusion and fluid-bed drying. (C) 1998 Academic Press.