Asian chestnut gall wasp confirmed in Michigan

Scout carefully for Asian chestnut gall wasps, follow quarantine rules prohibiting importing plant material from states with known infestations, and refrain from moving chestnut material between orchards.

Leaf distortion and gall formation caused by Asian chestnut gall wasp on chestnut. All photos by Dennis Fulbright, MSU

Leaf distortion and gall formation caused by Asian chestnut gall wasp on chestnut. All photos by Dennis Fulbright, MSU

Asian chestnut gall wasp (Dryocosmus kuriphilus) has been confirmed in chestnut orchards in southwest Michigan, including a small hobby farm and a university orchard, where it was initially detected and confirmed. At this time, management will focus on eradicating existing Asian chestnut gall wasp populations at these locations through insecticide applications and orchard removal.

In order to prevent further infestation, the quarantine prohibiting importing chestnut material from infested states remains in effect. Failing to comply with the quarantine could prove to have damaging implications for the Michigan chestnut industry and importers will be fined. The quarantine prohibits importing chestnut material (except seed) from Alabama, Connecticut, Georgia, Kentucky, Maryland, Massachusetts, North Carolina, Ohio, Ontario, Pennsylvania, Tennessee, Virginia or any other state or province where gall wasp becomes established. Exceptions are made if the nursery is certified as free from Asian chestnut gall wasp for three years. Check for an updated quarantine list before ordering materials. Review the complete provisions of the quarantine.

Origin and range of Asian chestnut gall wasp

Asian chestnut gall wasps are a potentially devastating invasive pest that can infest all species in the genus Castanea, including American chestnut, ornamental species and those planted for nut production. The Asian chestnut gall wasp is native to Asia and was first reported in the United States in 1974. It was observed on Chinese chestnut in Georgia after it was introduced on imported plant material. From Georgia, the geographic range expanded, reaching Virginia in 2001, Ohio in 2002, Kentucky in 2003, Maryland and Pennsylvania in 2006, Connecticut in 2011 and Massachusetts and Ontario in 2012. Asian chestnut gall wasps have continued to spread across eastern North America through natural dispersal and infested plant material, and was confirmed in Michigan in June 2015.

Life cycle and damage of Asian chestnut gall wasp

The gall wasp produces one generation per year via asexual reproduction. Adult females lay eggs inside buds in early summer and eggs hatch within the bud soon after. After egg hatch, larvae remain inactive in the bud until bud break the following spring, when they induce the formation of galls. Galls can form on the stem, petiole or leaf and provide the larvae and pupae protection. Adults emerge from galls in early summer and locate new chestnut shoots, laying eggs for the next generation. After the wasps emerge, galls become woody and dry out, potentially persisting on the tree for several years.

Asian chestnut gall wasps cause globular twig, shoot and leaf galls on actively growing shoots of all Castanea species. Galling reduces fruiting and nut yield, suppresses shoot elongation, reduces tree vigor and wood production and can kill trees. Galling also prevents infested shoots from producing new shoot growth and flowers, thereby reducing or eliminating future production.

As you cannot detect the buds where eggs have been laid, the movement of all chestnut materials – except seed – between orchards within Michigan, including scion wood and seedling rootstocks, should immediately cease. It is known that the cultivar ‘Bouche de Betizac’ is the only chestnut cultivar completely immune to Asian chestnut gall wasps.

Asian Chestnut Gall Wasp
Infested scion wood with galls.

Scouting for Asian chestnut gall wasps

The easiest way to scout for the Asian chestnut gall wasps is to visually inspect for galls. Scouting can take place at any time of the year as galls persist on trees even after wasps emerge in early summer. Leaves often remain attached to galls during winter, making them highly visible at that time. Michigan State University Extension encourages growers to scout often to ensure early detection to optimize management strategies.

Asian chestnut gall wasp on shoots
Galls persisting on leaves and shoots, girdling the tissue.

If you have located Asian chestnut gall wasps on your farm, please contact Mike Bryan, plant industry specialist at Michigan Department of Agriculture and Rural Development, at 517-284-5648, or myself at 231-944-6504 or .(JavaScript must be enabled to view this email address) for management assistance and to assist us in tracking possible movement of Asian chestnut gall wasps.

References

  • Oriental chestnut gall wasp, Anagnostakis, S.L., Payne, J.A., U.S. Department of Agriculture, Forest Service, Northeastern Area State and Private Forestry
  • Oriental chestnut gall wasp, Dryocosmus kuriphilus Yasumatsu (Hymenoptera: Cynipidae), Dixon, W.L., Burns, R.E., Strange, L.A., Entomology Circular No. 287, Florida Department of Agriculture and Consumer Service, Division of Plant Industry
  • Effects of gall formation by Dryocosmus kuriphilus on the growth of chestnut trees, Kato, K.; Hijii, N., Japanese Journal of Applied Entomology
  • Dryocosmus kuriphilus Yasumatsu (Hymenoptera: Cynipidae), an oriental chestnut gall wasp in North America, Payne, J.A.; Menke, A.S., Schroeder, P.M. USDA CEIR
  • Oriental chestnut gall wasp: new nut pest in North America, Payne, J.A., MacDonald, W.L., Cech, F.C., Luchok, J., Smith, H.C., eds. Proceedings of the American chestnut symposium
  • New nut pest: an oriental chestnut gall wasp in North America, Payne, J.A., Green, R.A., Lester, C.D., Annual Report of the Northern Nut Growers Association
  • Proceedings of the 17th Central Hardwood Forest Conference, Rieske, L.K., Cooper, R.W.
  • A new Dryocosmus injurious to chestnut trees in Japan (Hym., Cynipidae), Yasumatsu, K.

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.

Dr. Fulbright’s work is funded in part by MSU’s AgBioResearch.

Related Articles