XENOTEMNA PALLORANA (LEPIDOPTERA: TORTRICIDAE), A POSSIBLE ALTERNATIVE HOST FOR COLPOCLYPEUS FLORUS (HYMENOPTERA: EULOPHIDAE) USING ALFALFA GROUND COVER

IN ORCHARD SYSTEMS

Abstract

by Christopher Andrew Nobbs, M.S.

Washington State University

December 1997

Chair: Jay F. Brunner

The leafroller Xenotemna pallorana Robinson was reared on apple, cherry, pear, and alfalfa foliage. All of these host plants were suitable, however, development time and pupal weights were in some cases found to be significantly different. Adult females of this species were exposed to apple foliage in a no-choice situation and found to oviposit on the upper portion of the leaves. In a similar experiment, given the choice of apple or ground cover foliage including alfalfa, X. pallorana females preferentially selected alfalfa over the others.

Xenotemna pallorana was found to be a suitable host for the parasitoid Colpoclypeus florus Walker, when compared to a preferred host Choristaneura rosaceana (Harris) in both laboratory and field studies. There was found to be no parasitism preference between X. pallorana and C. rosaceana larvae by C. florus females. In both caged and open studies, C. florus preferred apple to ground cover habitats, although parasitism did occur in both. From these studies, it seems that X. pallorana could serve as an alternative host for C. florus in orchards without increasing the risk of crop loss. At the very least, X. pallorana and an alfalfa cover crop could be used as a model to study the potential of enhancing leafroller biological control in orchards by augmenting populations of an alternative host for a parasite instead of the parasite population.