SUSCEPTIBILITY OF CHILO-PARTELLUS SWINHOE (LEP, PYRALIDAE) EGGS TO ENTOMOPATHOGENIC HYPHOMYCETES

Egg masses of the stem-borer, Chilo partellus Swinhoe, were infected in the laboratory with conidial suspensions of four isolates of Beauveria bassiana (Balsamo) Vuillemin (ICIPE 1, 2, 4, 12), one isolate of Metarhizium anisopliae var. anisopliae (Metschnikoff) Sorokin (ICIPE 18) and two isolates of Paecilomyces fumosoroseus (Wize) Brown and Smith (ICIPE 10, 11). At a concentration of 10(8) condidia ml-1, all fungi tested, except ICIPE 1, caused more than 82% mortality. C. partellus larvae hatching from treated egg masses were also susceptible to all fungal strains, except ICIPE 10. Dose-mortality relationships were demonstrated for the most active isolates. However, deferred larval mortality from eggs treated with ICIPE 4 was 100% for all doses. The susceptibility of 12, 24, 48, 72, 96, and 120 h-old eggs to ICIPE 4 and ICIPE 18 was determined. The ability of the pathogen to infect decreased with the age of eggs; however, deferred larval mortality was not affected by the age of eggs. Results indicate that eggs could be the optimal stage for infection by the fungus. Among the fungi tested, isolates B. bassiana ICIPE 4 and M. anisopliae ICIPE 18 appeared promising for control of the early stages of C. partellus.