Stability of Conidia of an Entomopathogenic Fungus, Nomuraea rileyi , in and on Soil 1

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Abstract
The half-life of conidia of Nomuraea rileyi (Farlow) Samson layered on the surface of soil and exposed outdoors (at a rate equivalent to the number of conidia produced on a cadaver), was ca. 40 days. About 10% of the original infectivity was lost after 10 days and 99.9% was lost after 250 days of exposure. A residual infectivity of 0.1 % is equivalent to ca. 6 million conidia. In another study, the half-lives of conidia buried and on the soil surface were 90 and 65 days, respectively. After 11 days of exposure, 10% of the original infectivity was lost from both the buried and soil-surface samples, respectively; after ca. 350 and 450 days, ca. 99% was lost in the buried and soil-surface samples, respectively. Results from both studies indicate that conidia can overwinter in the soil and that enough viable conidia to initiate an epizootic are available from larvae that died the previous field season.