Current Gypsy Moth Situation in Iowa

Iowa was very fortunate for over two decades in that we had no substantial establishment of gypsy moth in spite of the ease with which this pest migrates on cars, trucks, buses, recreational vehicles and interstate merchandise shipments. It at first appeared our luck had changed with a large introduction of gypsy moth egg masses on infested nursery stock last spring, but, as the following update, based on information provided by Dr. Catherine Thompson, an Entomologist with the Iowa Department of Agriculture and Land Stewardship indicates, the situation is not as bad as it could have been.

Slightly more than 1200 infested blue spruce trees from a nursery situated in a heavily infested region of Pennsylvania were received by three Iowa nurseries in the spring of 1991. All 400 of the infested trees received by Sutherlands Lumber Stores in Des Moines were sold. A media campaign by IDALS that began as soon as the introduction was detected has been very successful and the locations of over 60% of those trees have been reported by tree purchasers. The trees received by Natural Plus Nursery of Clear Lake were used at landscaping job sites and the location of all sold trees is known. Three hundred of the trees remained at the nursery and they were sprayed this spring with the microbial insecticide (Bt) in an eradication attempt.

Inspections and regulatory activities by IDALS indicate reason for cautious optimism regarding this introduction. Burlap band caterpillar traps were placed on and/or near the infested trees and caterpillars were caught this spring during the caterpillar period (May through June) at only two sites. One was in Dallas County and the other in Cerro Gordo County where 100 infested spruce trees had been planted. Both sites are now heavily trapped with pheromone traps to closely monitor the presence of any adult moths.

The rest of the state is also being heavily trapped this summer with 4,769 traps placed around the state. This is the largest trapping program ever in Iowa with 16 people employed by the USDA or state of Iowa to trap gypsy moths. Nearly one fourth of the traps are set in Polk County where the greatest chance of yet undetected infestations exists. As of July 15th, no moths have been caught. It is assumed the moths are slightly late this year because of unseasonably cool temperatures.

The only other gypsy moth infestation in Iowa is at Long Grove (Scott County) where gypsy moth egg masses were introduced with the moving of a family~s personal belongings from New Jersey. That infestation was detected by the routine trapping program in 1990, the situation monitored in 1991 and a bacterial spray treatment applied this past spring during the caterpillar season. Heavy trapping will continue in that area as well.

For more information on the life cycle and biology of the gypsy moth, see publications Pm-1091 or Pm-1481.

This article originally appeared in the July 22, 1992 issue, p. 131.


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