PREMORTALITY EFFECTS OF ZOOPHTHORA RADICANS INFECTION IN PLUTELLA-XYLOSTELLA

The effect of Zoophthora radicans infection on food consumption and ut ilization by Plutella xylostella larvae and oviposition by adults was investigated. Larval food consumption and weight gain were not affecte d by Z. radicans until the third day after infection, 1 day prior to d eath from mycosis. No food was eaten on the day on which larvae died. Overall, infected larvae ate 44% less leaf tissue than control larvae. Of the leaf tissue consumed by infected larvae 87.5% was eaten on the first 2 days after infection and after this time infected larvae gain ed Little weight, The efficiency with which ingested food was converte d into body weight did not change as infection progressed. Infected fe male moths laid significantly fewer eggs than control moths. This diff erence was not only due to differential mortality between the infected and control treatments as the egg production by infected females, unt il the point of death (Day 4 after infection), was significantly less than that of control females over the same period. Incubating females for 24 hr after eclosion (to allo ce further egg maturation), prior to infection, did not result in greater overall egg production when comp ared with moths infected on the day of eclosion. The possible causes f or these reductions in larval feeding and adult oviposition rates are discussed. (C) 1997 Academic Press.