Forest Resource Protection Forest Health, Insect & Disease Forest Fire Control Staff

Vermont 2006 Forest Tent Caterpillar Sugarbush Spray Project

Summary of Results

Net defoliation (average defoliation that occurred after spraying) was 9 percent, similar to the 7% achieved in 2005.  This is based on 5 trees per block for 19 of 24 blocks but does not include a number of spray blocks where moderate to heavy defoliation occurred but timing of some of the defoliation estimates was inadequate for determining net defoliation.  In one case, the final prespray defoliation estimate was not close enough to spray day to be useful and in another case, the final defoliation estimate was taken before defoliation was complete. In several cases, final defoliation estimates were made well after complete refoliation without including the refoliation in the estimate. 

Prespray and postspray defoliation for the 19 blocks is graphed below. 

Conclusions

Eight of the spray blocks (42%) ended up with at least moderate defoliation but most of these had high initial defoliation due to weather-related delays, were in the warmer climatic zones and had high population pressure.  Observations of field personnel indicated that most spray blocks had many dead caterpillars and spraying stopped or slowed down the defoliation.

VT Dept. Forests, Parks & Recreation, 12/11/ 2006.