ARS | Publication request: Biological control of emerald ash borers: the role of indigenous North American parasitoids

Submitted to: Emerald Ash Borer Research and Technology Development Meeting
Publication Type: Proceedings
Publication Acceptance Date: April 30, 2010
Publication Date: N/A

Technical Abstract: Field surveys of the emerald ash borer (EAB), Agrilus planipennis Fairmaire, and associated parasitoids were conducted in Cranberry Township, PA; Granville, PA; and Cheltenham, MD. Several species of parasitic Hymenoptera were collected from EAB-infested green ash trees or reared from late-instar EAB larvae, prepupae, and/or pupae. These included Balcha indica (Mani & Kaul), Eupelmus pini Taylor [Eupelmidae], Atanycolus vitticrus Townes, Atanycolus sp., Spathius laflammei Provancher [Braconidae], Dolichomitus vitticrus Townes [Ichneumonidae], and two additional unidentified ichneumonids, Orthizema sp. Townes and Cubocephalus sp. Townes. Together, these parasitoids caused about 5% parasitism of EAB in the field. The most abundant species was B. indica accounting for 82% of all parasitoids recovered during our survey. Subsequent laboratory assays confirmed that B. indica and E. pini, are solitary ectoparasitoids of EAB larvae, prepupae and/or pupae. In addition, both B. indica and E. pini reproduce through thelytokous parthenogenesis; i.e., virgin females produce daughters. These parasitoids may be complementary to the current classical biological control programs against EAB in North America, which has been focusing primarily on the introduction of exotic larval and egg parasitoids from China. Because of the low parasitism, prospects for successful natural control of EAB appear slim, so the classical approach appears to be the most promising biological control avenue to pursue at this time. As evaluation of interagency classical biological research in progress continues, parasitism by indigenous species should be monitored to see whether its incidence increases over time.