LIGHT-BROWN APPLE MOTH, EPIPHYAS-POSTVITTANA (WALKER) .3. DIFFERENCES IN SUSCEPTIBILITY TO A NUCLEAR POLYHEDROSIS-VIRUS

A nuclear polyhedrosis virus (NPV) was found to be widespread throughout the distribution of the light‐brown apple moth (LBAM), Epiphyas postvittana (Walker), in southeastern Australia. Tests were done on sample cohorts drawn from laboratory strains and field populations to determine whether (i)susceptibility to NPV varied significantly in LBAM; and (ii) responses which exposure to the virus was known to elicit in the CAN Laboratory Strain (Geier & Oswald 1977) could be regarded as typical of the species. It was shown that discrete breeding groups could differ greatly in the relative mortality which they sustained following similar exposures to NPV. Whereas more females died than males in all virus‐treated cohorts, as had been previously established in the CAN Strain, the demographic impairment typical of many individuals surviving exposure to NPV in that very tolerant strain (reduced weight of females, reduced fecundity and fertility) was not generally manifest in more susceptible forms of the species. Field surveys so far have not been detailed enough to reveal distribution patterns in the host‐pathogen relationship. The epidemiology of the virus is unknown and its role in the life system of LBAM is not understood. Copyright © 1979, Wiley Blackwell. All rights reserved