NORTHERN NUT GROWERS ASSOCIATION, INC.

Oriental Chestnut Gall Wasp Found in N. E. Ohio
by Bob Stehli

The presence of Oriental chestnut gall wasp (Dryocosmus kuriphilus) in the N. E. Ohio city of Broadview Heights has been confirmed by Ohio State Entomologist Dr. David Shetlar. The discovery was made in early July by the author, an NNGA member, while visiting relatives in that city.

The infestation seems to be confined to four large Chinese chestnut trees within about 1/4 mile of each other. Two of these trees have a few old galls on them from last year. The source of the infestation is unknown, but it was most likely a mail-order seedling chestnut that had gall wasp eggs deposited in the dormant buds.

Galls on American Chestnut
Figure 1. Galls on American chestnut.

Oriental gall wasp first appeared in the United States in 1974. It arrived on cuttings from Asia.1 The gall wasp spread quickly throughout Georgia, where it was accidentally introduced, wiping out the state's fledgling chestnut industry. It continued to spread in all directions reaching as far north as McMinnville TN by 2001. McMinnville is a major nursery area, and the source of many of the chestnut seedlings sold in mail-order catalogues. In the meantime the United States Department of Agriculture, with the guidance of Dr. Jerry Payne, introduced several natural enemies of the Oriental gall wasp--one of these, a parasitic wasp, has been very successful in controlling the Oriental gall wasp in the South.

Galls on American Chestnut
Figure 2. Oriental gall wasp laying eggs in bud of Chinese chestnut. Newly emerged wasps are approximately 1/8 inch in length.

The problem we face with the Ohio infestation is that it almost certainly arrived without the predatory wasp that controls it, and will therefore rage out-of-control, spreading up to 30 miles per year once established, until it either meets the Northern front of the Southern infestation, or is controlled by the introduction of its natural enemy, the parasitic wasp.

It has been exasperating to the author to witness the glacial speed with which government agencies move to control exotic pests. In a year or two, when they have studied this infestation to death it will be too late to stop it; in fact, as I write this article (7/19/03), the Ohio gall wasps are beginning to emerge from the galls, and fly off to lay their eggs in the buds of any chestnut trees they can find, of which there are plenty to choose from in N. E. Ohio.

No effective chemical method of control has ever been found for Oriental chestnut gall wasp. Left unchecked the pest will kill or severely weaken most Chinese, European, and American chestnut trees, nearly eliminating nut production.

For additional information about the Oriental gall wasp, see http://www.gacaps.org/pests/gallwasp.html

For a 2006 update on the Oriental gall wasp in Ohio, click here.

1 Anagnostakis, S. L. (1998), "Chestnuts in Georgia," 89th Annual Report of the Northern Nut Growers Association, Inc., Painesville, OH, July 26 - 29, 1998.

Photos by Dr. Jerry A. Payne, reproduced with permission.



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