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Title: IMPROVED REARING AND RELEASE PROCEDURES FOR COTESIA MELANOSCELA (HYM.: BRACONIDAE), AN EARLY SEASON PARASITOID OF LYMANTRIA DISPAR (LEP.: LYMANTRIDAE)

Author
item Webb, Ralph
item VENABLES, L - MARYLAND DEPT AGRICULTURE
item Thorpe, Kevin

Submitted to: Entomophaga
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/15/1997
Publication Date: N/A
Citation: N/A

Interpretive Summary: Cotesia melanoscela is an early-season parasitoid of the gypsy moth, a serious defoliator of shade trees, parks, and forests in eastern North America. Since C. melanoscela is easily reared, lacks synchrony with its host in its second, or summer, generation, and is extensively hyperparasitized, there has been considerable interest in the augmentative release of this parasitoid to suppress host populations. The work reported here adapts previously published methods as a basis for implementing further improvements in mass rearing this potentially important biological control agent for the gypsy moth. In addition, this research extends earlier studies regarding early season field release of parasitoid cocoons. This technique offers significant logistical, cost, and efficacy improvements over earlier methods of releasing parasitoid adults. Ultimately, this paper brings this tactic one step closer to practical use as a pest management tool. Potential users of this technology include all parties interested in the use of IPM strategies against the gypsy moth including land managers at the community, county, and state levels, park managers, military base managers, etc.

Technical Abstract: Rearing and release procedures for Cotesia melanoscela (Ratzeburg) (Hymenoptera: Braconidae), an early-season parasitoid of Lymantria dispar (L.), were evaluated in 1995 and 1996 at the Beltsville Agricultural Research Center, Beltsville, Maryland, USA. Mass rearing procedures were developed during the winter/spring of 1995/1996 to produce diapausing C. melanoscela cocoons for experimentation. Program efficiency as measured by percent adult emergence was estimated to be 84% with a measured sex ratio of 48:52 M:F, at an estimated cost per 1000 cocoons of $5.26 for materials and a labor requirement of approximately 6 hours. A host larvae:female parasitoid ratio of 100:1 was found to be most efficient in terms of number of parasitoid cocoons produced per female parasitoid, but a ratio of 100:2 was most efficient in terms of number of cocoons per rearing cup. Placement of C. melanoscela cocoons overwinter under natural conditions for 25 weeks (November placements) before expected L. dispar egg hatch (mid-April) resulted in excellent synchrony with host egg hatch. Alternatively, holding C. melanoscela cocoons in cold storage for 23 or more weeks at 5øC resulted in adult parasitoid emergence beginning 10 days after removal from cold storage, and proper timing of removal would result in similar synchrony of adult emergence with host egg hatch. The two alternative release strategies give managers increased program flexibility.