Progress made in addressing Asian chestnut gall wasp

Permits to combat the Asian chestnut gall wasp through classical biological control have been issued to Michigan on state and federal levels.

Female Asian chestnut gall wasp on chestnut petiole affected by gall. Photo credit: Erin Lizotte, MSU Extension

Female Asian chestnut gall wasp on chestnut petiole affected by gall. Photo credit: Erin Lizotte, MSU Extension

Asian chestnut gall wasp (Dryocosmus kuriphilus), a potentially damaging invasive pest of Castanea species, was confirmed in chestnut orchards in southwest Michigan in July 2015. Chemical control of Asian chestnut gall wasp is difficult as the period of adult flight is brief and immature stages of the insect are protected inside plant tissues.

In its native China, Asian chestnut gall wasp is kept in check by natural enemies, including the parasitoid Torymus sinensis. T. sinensis was introduced for Asian chestnut gall wasp control in Georgia in the 1970s and is now well-established in parts of the eastern United States. According to research by Lynne Rieske-Kinney from the University of Kentucky, T. sinensis has expanded its geographic range in the United States along with expanding gall wasp populations. The parasitoid produces one generation per year; adults emerge in early spring and parasitize newly developing galls before they are visible to the naked eye. The parasite overwinters in old galls as larvae and pupae, emerging in spring in time to parasitize newly forming galls. This synchrony with the Asian chestnut gall wasp life cycle contributes to the efficacy of the parasitoid and makes for a potentially highly effective and environmentally sustainable management method. T. sinensis has been found in Michigan and efforts are underway to monitor Asian chestnut gall wasp and T. sinensis populations.

In other areas of the United States, T. sinensis is redistributed by moving infested gall material between sites with the hopes of improving Asian chestnut gall wasp suppression. To better position Michigan growers to protect their orchards through the potential introduction of T. sinensis, approval from the United States Department of Agriculture as well as Michigan Department of Agriculture and Rural Development for the movement of T. sinensis into and within Michigan has been secured by Ernest Delfosse in the Department of Entomology at Michigan State University. This is a critical step in preparing to address the potential destruction caused by Asian chestnut gall wasp and builds upon the important distribution and identification work by MSU Diagnostics Services, Michigan State University Extension field personnel and MSU AgBioResearch scientists.

For more information on Asian chestnut gall wasp scouting and management, refer to the MSU Extension article, “Asian chestnut gall wasp confirmed in Michigan.”

This material is based upon work supported by the National Institute of Food and Agriculture, U.S. Department of Agriculture, under Agreement No. 2013-41534-21068. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture.

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