NATURAL OCCURRENCE OF AND INOCULATION EXPERIMENTS WITH CONIDIOBOLUS-CORONATUS AND CONIDIOBOLUS SP IN GLASSHOUSE POPULATIONS OF BEMISIA-TABACI

Bemisia tabaci (Gennadius), the sweetpotato whitefly, has only one kno wn entomophthoralean pathogen, Erynia radicans (Entomophthoraceae). Tw o new pathogens have been isolated recently from a glasshouse populati on of this pest: Conidiobolus coronatus and another, undescribed speci es of Conidiobolus (Entomophthorales: Ancylistaceae). Artificial inocu lation experiments revealed that eggs of B. tabaci are practically imm une to infection by either species. Second-instar larvae are highly re sistant, only high doses of conidia causing between <1% and 4.6% morta lity. Adults were found to be much more susceptible. Doses of 60 conid ia/mm2 of C. coronatus caused average mortalities of ca 95%. The maxim um mortality of adults caused by Conidiobolus sp. was much lower, ca 3 0%, at a dose of 210 conidia/mm2. The incubation period (inoculation t o death) for both species, under our experimental conditions, is very short: 18-24 h for C. coronatus and 30 h for Conidiobolus sp. Both fun gi produced loricoconidia (conidia metamorphosed into resting spores) on cotton leaves and other dry surfaces. This ability allowed Conidiob olus sp. to remain viable for 17-21 days on cotton leaves, in glasshou se conditions and in the absence of hosts, while C. coronatus persiste d for 10-14 days.