The effects of duration of development and drying regime on the longevity of conidia of Metarhizium flavoviride

Conidia of the entomopathogenic Metarhizium flavoviride were harvested 8, 1 0, 12 or 15 d after inoculation at 25 degrees C and then (as conidiated ric e) dried rapidly (10-12% r.h. and 17-20 degrees For 17 h to about 15-22% mo isture content) or slowly (50-60% r.h. and 27 degrees for 5 d to about 27-3 2% moisture content initially). The subsequent survival of these conidia in air-dry storage at 50 degrees with 8.1% moisture content was then assessed . Conidia longevity (assessed by the duration of storage until conidia viab ility was reduced to 50%, p(50)), was maximal when conidia were harvested 1 0 d after inoculation, and was much greater following slow rather than rapi d drying. The substantial beneficial effect of slow desiccation to subseque nt conidia survival is consistent with that detected in other propagules in anhydrous biology, and is also of considerable practical utility for the b iological control of insects by entomopathogenic fungi.