LONG-TERM STORAGE OF METARHIZIUM FLAVOVIRIDE CONIDIA IN OIL FORMULATIONS FOR THE CONTROL OF LOCUSTS AND GRASSHOPPERS

Freshly harvested conidia of Metarhizium flavoviride (Gams & Rozsypal) were stored in two vegetable oils, groundnut oi soya, or a miner-al o il, Edelex. They were diluted with either Shellsol K or deodorized ker osene, and antioxidants were added to half of the vegetable oil formul ations. Dried non-indicating silica gel was added to half of the formu lations before storage at 8 or 17 degrees C. Undried conidia, those wi thout silica gel. lost viability rapidly with germination dropping bel ow 40% after 9 and 32 weeks at 17 and 8 degrees C respectively. After 127 weeks (ca. 30 months) in storage, germination remained at over 60 and 80% for the dried formulations at 17 and 8 degrees C respectively (after an unexplained drop in germination after 16-18 months in storag e). Comparable figures for 160 weeks (ca. 37 months) were 47 and 68%. These figures represented germination after 24 h of incubation; after 48 h of incubation, germination was 79 and 89% from samples stored for 160 weeks at 17 and 8 degrees C respectively. Representative formulat ions of the stored conidia were tested in bioassays against the desert locust Schistocerca gregaria (Forskal) up to 30 months into the exper iment, and were Sound to have retained full virulence compared with fr eshly prepared formulations.