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Title: EFFECT OF SEASONAL PLACEMENT OF COTESIA MELANOSCELA (HYMENOPTERA: BRACONIDAE) ON ITS POTENTIAL FOR EFFECTIVE AUGMENTATIVE RELEASE AGAINST LYMANTRIA DISPAR (LEPIDOPTERA: LYMANTRIIDAE)

Author
item WIEBER, ANNE - DECEASED
item WEBB, RALPH
item Ridgway, Richard
item THORPE, KEVIN
item REARDON, RICHARD - USDA FOREST SERVICE
item KOLODNY-HIRSCH, DOUGLAS - BIOSYS CO
item TATEMAN, KATHLENE - MD DEPT AG

Submitted to: Entomophaga
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/21/1996
Publication Date: N/A
Citation: N/A

Interpretive Summary: Cotesia melanoscela is an important early-season parasitoid of the gypsy moth in Maryland. High levels of hyperparasitism (parasitism of parasites) commonly reach over 90 percent in nature. As discussed in this paper, C. melanoscela has a number of attributes that indicate it would be a good candidate for augmentative or yearly release against gypsy moth populations. We found that timing of placement of C. melanoscela cocoons in the field has profound effect on the number of adults emerging at the appropriate time, i.e., when susceptible young gypsy moth caterpillars are present. We concluded that November/December releases avoided natural enemies and promoted appropriate diapause and post-diapause development that enhanced survival and synchrony of adult emergence with host stage susceptibility. Results should benefit scientists seeking to develop technology for elminating low level gypsy moth populations in quarantine situations.

Technical Abstract: Cohorts of the gypsy moth parasitoid Cotesia melanoscela cocoons were exposed in the field at three Maryland locations to attack by natural enemies for two week periods, then were held in an outdoor insectary until C. melanoscela adults or hyperparasitoids emergence occured. The timing of the placement of the cocoons in the field had a profound effect on the number of C. melanoscela that survived and emerged as adults in synchrony with the field occurrence of susceptible early-instar gypsy moth larvae. The proportion of emerged adults available concurrent with susceptible host stages ranged from 1-92 percent, depending on placement date. November or December placements of C. melanoscela cocoons were most effective with 74-92 percent emergence of adults during peak periods of susceptible host stages. Spring placements were least effective. The causes of ineffective placement, which varied with location and date, were program (handling) loss, non-emergence, attack by hyperparasitoids, invertebrate predation, and C. melanoscela adult emergence at times when appropriate gypsy moth life stages would not be present.