Monday, December 10, 2007 - 10:53 AM

Non-target impacts of introduced parasitoids are inconsistent across species of native Hawaiian leafroller moth (Crambidae: Omiodes)

Cynthia B. A. King,, University of Hawaii, Dept. of Plant and Environmental Protection Sciences, 3050 Maile Way, Gilmore Hall 310, Honolulu, HI and Daniel Z. Rubinoff,, University of Hawaii, Plant and Environmental Protection Sciences, 310 Gilmore Hall, 3050 Maile Way, Honolulu, HI.

When two species of endemic Hawaiian Omiodes became pests of economic significance in sugarcane and coconut palm, an array of biological control agents were introduced to suppress their populations. Subsequent declines were documented not only in the pest species but across the genus, culminating in the listing of two-thirds of the other 21 Omiodes species as extinct or possibly extinct by the U.S. Fish and Wildlife Service and other agencies. The declines were attributed primarily to the impacts of introduced parasitoids, despite that habitat destruction and host plant disappearance have also affected populations. In the last six years, five extinct species have been “rediscovered,” and additional research has documented the persistence of some Omiodes species in spite of extreme pressure from introduced parasitoids. The objective of this research was to quantify parasitism rates in non-target Omiodes species using controlled exposure trials and rearing of field collected larvae. Field trials were conducted on Maui in summer 2006, and spring and summer 2007, using eggs and larvae of O. continuatalis. Trial data indicate parasitism rates of less than 1% (n>1200) in sentinel larvae, in contrast to rates greater than 30% (n>300) observed in field collections of other Omiodes species over the same period. It remains unclear why apparent parasitism differs so greatly from observed parasitism rates in exposure trials, however species-specific behavioral and/or physiological adaptations may help explain the disparity.

Species 1: Lepidoptera Crambidae Omiodes continuatalis (Hawaiian leafroller moth)