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News Release 6-18-2001

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WHITE OAKS HAVE GALLS, NOT BLIGHT

For Immediate Release June 18, 2001

CHARLESTON, WV — According to Commissioner of Agriculture Gus R. Douglass, white oak foliage in central and west-central counties is turning brown because of a heavy infestation of galls, not blight. Reports of damaged white oak foliage have been received from Harrison, Doddridge, Ritchie, Wood, Jackson, Kanawha, Putnam, Roane, Gilmer, Wirt, Calhoun, Lewis, Braxton and Clay Counties to date. Lightly infested trees have discolored foliage. Severely infested trees have browned off and foliage is dropping prematurely. Douglass stated that there is no record of outbreak occurrences or damage from this gall insect in West Virginia prior to this summer.

Adult gall wasps, Neuroterus saltatorius sp., laid eggs on buds this spring resulting in the formation of the small, button-shaped galls on the leaves. Life cycle information on a similar species indicates the first generation completed its life cycle by mid-May. The second generation is currently in the gall stage. There are two generations per year. The young galls are green and turn brown as they mature. Each gall has a single immature wasp inside. When mature, the galls fall off the foliage leaving small pits in the underside of the leaves where they were attached. The galls drop to the ground where pupation occurs. Second generation adults overwinter inside the galls and will emerge next spring. The wasps are very tiny (1.0-1.5 mm long) and do not sting.

"There are lots of gall insects on oak and, generally speaking, they are usually more of a cosmetic problem than actually being damaging," said West Virginia Department of Agriculture (WVDA) Forest Entomologist Sherri Hutchinson. "However, this spring we are having extremely heavy populations of this gall wasp in several counties, and severely infested trees are prematurely dropping leaves. The trees might put out a second set of leaves, but regardless, defoliation this early in the season will stress the trees and retard growth to some extent."

Once the gall has formed, control measures are not effective or necessary. Small yard trees or nursery trees could be sprayed in mid-May next year with a systemic pesticide, but this is not practical in a wild forest.

Surveys are under way to document the distribution of the gall wasp outbreak in West Virginia. If you notice the gall wasp in a county not already listed, write the WVDA, Plant Industries Division, 1900 Kanawha Blvd., East, Charleston, WV 25305-0191 or call 304/558-2212.

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