Effects of storage on viability and efficacy of granular formulations of the microbial herbicides Alternaria alternata and Trematophoma lignicola

Alternaria alternata Pesta (gluten matrix) granules stored at 12% relative humidity were still viable and infective, giving total control of Amaranthu s retroflexus after 24 months storage. Viability of the propagule in the gr anule was an important factor of the evaluation test and not just the viabi lity of the granule. The concentration of inoculum in the granule was impor tant, with 10(5) to 10(6) conidia g(-1) being the ideal, since lower concen trations may not be able to out-compete the soil micro-flora. Even with soi l application, the effect of local humidity was still important. Trematopho ma lignicola was also formulated as microbial herbicide granules but the co nidia were severely damaged in the production process.