Submitted to: Entomological News
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 3, 2001
Publication Date: N/A
Interpretive Summary: The gypsy moth is a serious defoliator of forest and shade trees. One of the natural enemies that has been imported into North America to help control the gypsy moth is a Braconid wasp, Cotesia melanoscela, that has a number of attributes that indicate that it would be a good candidate for augmentative release against the gypsy moth. Unfortunately, this wasp is itself attacked by a large number of hyperparasitoids that drastically reduces its potential for gypsy moth control. A thorough understanding of the makeup of the hyperparasitoid complex attacking C. melanoscela is needed to develop release protocols that will facilitate its escape from its hyperparasitoid complex. The present paper reports on an aspect of the biology of some of the 20 species of hyperparasitoids found active in Maryland against C. melanoscela. The species were found to follow several different strategies in partitioning the emergence of their progeny throughout the year. Understanding the emergence patterns of these hyperparasitoids will give insights into the best timing for augmentative release of C. melanoscela as well as insights on the nature of hyperparasite complexes in general. Results should be useful to agencies contemplating the release of C. melanoscela as well as to general studies of parasitoid release into an environment rampant with hyperparasitoids.
The pattern of progeny adult emergence from parasitized C. melanoscela cocoons as a function of month of attack is compared for its more prominent hyperparasitoid species. Several strategies for apportioning progeny adult emergence to meet the challenges and opportunities of within-season (horizontal) and overwinter (vertical) propagation were found and elucidated. The simplest strategy was to produce new broods all year long without a diapausing generation. A strategy used by several species was to produce a series of new broods until late summer, and then to produce a brood that undergoes diapause. A more complex strategy was used by a species, which, beginning in late spring, partitioned its progeny so that some emerged as an immediate summer generation, while others entered diapause and emerged in the spring. The most complex strategy was to, beginning in late spring, partition the progeny so that some would emerge as adults for an immediate summer generation and others would emerge in September to bolster the adult population that produced the diapausing generation.