POTENTIAL APPLICATION OF THE ENTOMOPATHOGENIC FUNGUS, NOMURAEA-RILEYI, FOR CONTROL OF THE CORN-EARWORM, HELICOVERPA-ARMIGERA

The entomopathogenic fungus, Nomuraea rileyi, caused 90.5-100% mortali ty in fourth-instar larvae of the corn earworm, Helicoverpa armigera, when applied at 10(7) conidia/ml to corn silks, and leaves of soybean, tomato and chrysanthemum. The LT50 was 5.9-6.7 days. The fifth-instar larvae showed a mortality of 94.6% on soil with 20% water content, an d 41.7% on 10% water content when the soil surface was sprayed with 10 (8) conidia/ml suspension. Five fungicides, eight insecticides and nin e herbicides, which are commonly used in corn fields, were evaluated f or inhibition to conidial germination by a paper disk test. Among them , only two fungicides, viz., maneb and propineb, were highly inhibitor y, while insecticides and herbicides examined were not inhibitory to t he fungus. Field applications of N. rileyi conidial suspension to neon ate larvae were found to be as effective as 40.46% carbofuran (EC) at 800-fold dilution in controlling corn earworm based on marketable ears . It is thus suggested that N. rileyi has potential to be a microbial control agent for this insect.