FTC parasites and predictions for 2003

The main FTC outbreak is over, but there will be some large areas where FTC will linger in bothersome numbers, especially where the moths expanded into new territories last year and where their natural enemies were minimal. Another type of situation where FTC could remain a problem is where night lights attracted moths from surrounding areas, concentrating them on nearby trees and shrubs. See map for predictions for defoliation in 2003 based on egg mass collections. More information on FTC can be found at Minnesota DNR: Backyard tree care.

Egg masses collected April 23rd in four northeastern Minnesota locations revealed few or no egg parasites:

  1. west side of Hibbing 0, 18% parasitized;
  2. Grand Rapids?0. 0. 3. 3. 4% parasitized;
  3. east side of Deer River?2, 0, 0, 0% parasitized; and,
  4. west side of Virginia?0, 0, 1.3% parasitized.

The egg parasites were identified as Telenomus clisiocampae, small wasps. Thanks to John Luhman, Entomologist for MDA and Dan Hanson, Entomologist at the University of Minnesota, for identification of egg and pupal parasites. We appreciate your help.

Forest tent caterpillar eggs hatched May 5th through the 9th in the Garrison, Brainerd and Grand Rapids areas. As of May 30th, FTC caterpillars were up to 1 inches long in Grand Rapids.

Three species of parasitic flies that helped cause the FTC population decrease last year were Sarcophaga aldrichi, Lespesia spp., and Leschenaultia exul. Friendly flies (S. aldrichi) were by far the dominant parasite of cocooning FTC. We expect that the friendly flies will be extremely abundant this year and a much bigger nuisance than the caterpillars, particularly in locations that had heavy defoliation last year. The flies usually start to show up in late May and may last into August, but they are usually most abundant from mid-June to mid-July. Information on the friendly fly can be found on the DNR website. And, regardless of all the rumors to the contrary, these flies are native and have never been raised or released by the DNR or anyone else.

Map showing predicted 2003 FTC deforestation in Northeast Minnesota.