Susceptibility of Diamondback moth (<i>Plutella xylostella</i> (L)) larvae to the entomopathogenic fungus <i>Zoophthora radicans</i> (Brefeld) Batko

Abstract

The fungus Zoophthora radicans is being developed as a biopesticide for control of diamondback moth (Plutella xylostella) A series of laboratory doseresponse bioassays was used to determine the virulence of five isolates of Z radicans to diamondback moths indigenous to New Zealand A reference isolate from Malaysia was compared to four isolates from New Zealand Late second and early third instar diamondback moth larvae were exposed to discs of broccoli leaves that had previously been inoculated with increasing densities of fungal conidia Isolates from New Zealand were consistently more infective than the Malaysian isolate LC50 values ranged from 092 conidia/mm2 for isolate NW337 (New Zealand) to 697 conidia/mm² for NW250 (Malaysia) Resting spores were found in up to 30 of the total number of larvae that succumbed to infection with the New Zealand isolates but were never found in larvae that succumbed to infection with isolate NW250 A single isolate was identified with potential for future testing under field conditions