NAVEL ORANGEWORM (LEPIDOPTERA, PYRALIDAE) DEVELOPMENT IN SUNBURNED WALNUTS

Navel orangeworms, Amyelois transitella (Walker), completed developmen t in sunburned walnuts late in the growing season, but moths did not e merge until after harvest. Sunburned walnuts were not attractive to ov ipositing moths until considerable hull damage occurred. Only sunburne d walnuts with undamaged kernels were suitable for larval development. Navel orangeworm infestation levels up to 38% were recorded in sunbur ned walnut samples from the San joaquin Valley, CA. Nut hull tissue da maged by sunburn was not selected over undamaged hull tissue for moth oviposition. Mean kernel temperatures of sunburned walnuts were higher than both undamaged walnuts and ambient air temperature. Premature hu llsplit occurred in sunburned walnuts of both early and later maturity varieties. These data suggest that, although sunburned walnuts contri bute to the seasonal buildup of navel orangeworms, the late developmen t of navel orangeworms in these nuts reduces the incidence of infestat ion in hullsplit, new crop nuts.