Landscape - Tent Caterpillar Season Coming Up

Tent caterpillar season is fast approaching. The following is some information on this pest from the Kentucky Pest News.

Eastern tent caterpillar (ETC) egg hatch should be complete by early April. Small ETCs move to feed on expanding leaves and build tents at branch and limb forks. Initial growth of the caterpillars will be slow but during the latter part of April caterpillars in limb nests will begin to move to main trunk branch angles and join in a smaller number of larger tents on individual trees. This aggregation behavior can be used to advantage in managing the insect by physically destroying or treating accessible aggregations. Caterpillars will leave defoliated trees in search of food on which to complete development. When full grown, they will wander to find a pupation site. In either case, successful control of dispersing caterpillars is difficult.

Foliar sprays for caterpillar control can be made during this time period, as well. Spray residues of products based on Bacillus thuringiensis (Bt) must be eaten by small caterpillars to be effective; there is no contact effect. Consequently, applications should be made to as much of the canopy as is feasible, especially the foliage around active nests. Direct application to nests will not provide any control. Bt residues on foliage can be broken down by sunlight in 3 to 4 days so it is important to assess control and re-treat if necessary. Effectiveness of Bt decreases as caterpillar size increases.

Foliar sprays with products such as bifenthrin (Talstar) or carbaryl (Sevin) have both stomach and contact activity so they can be effective when sprayed on to foliage or tents. The residual life of carbaryl is about a week; that of bifenthrin is at least 2 to 3 weeks. Another option is to inject trees with either bidrin (Inject-A-Cide "B" or 2% Abacide. Regardless of the treatment used, it is important to re-visit the sites in about 5 days to assess caterpillar activity.

Adapted from an article by Lee Townsend in the April 2, 2007 edition of the Kentucky Pest News from the University of Kentucky, College of Agriculture.