The longevity of conidia of three insect-parasitizing hyphomycetes
The longevity of conidia of Beauveria bassiana, Paecilomyces farinosus and Metarrhizium anisopliae decreases as the temperature of storage is increased from 8 to 25°C., and is also reduced by exposure to light. Conidia of B. bassiana and P. farinosus lose the ability to germinate sooner at high storage humidities than at low. By contrast, those of M. anisopliae survive longest at high and low humidities and least at median humidities close to 45% r.h. If conidia of M. anisopliae are washed before storage, the least favourable storage humidity then rises to about 65% r.h. Very quick washing in water at 0° suffices to produce this change, which is independent of whether final equilibration with the storage humidity is achieved by loss or gain of water. The unfavourable effect of median humidities is reduced or suppressed in spores stored in air enriched with carbon dioxide or devoid of oxygen. The results are discussed in terms of the possible induction of differences in the rate or course of metabolism in the stored spores which might affect their viability
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