Yes, it’s that time of year again when we face the return of the Western Tent Caterpillars. As soon as their eggs hatch in April or May, the caterpillars begin eating leaves and create “tents” – white, silky shelters that cover the forks and tips of tree branches and shrubs. During warmer weather they feed mostly at night and return to their tents during the day.
They are often seen in chokecherry bushes and red leafed ornamental chokecherry trees. The caterpillars are easy to recognize. They have a yellow checkered pattern with a blue dotted line down their backs.
Ways to control tent caterpillars:
- During early spring pruning, inspect the trees for tent caterpillar egg masses. These masses appear as swellings on small, bare twigs. Through normal pruning, you can often remove tent caterpillar eggs before they hatch.
- Prune twigs containing webs when you first notice them in the spring. Place the branches in sealed plastic bags and dispose of. If they are in areas where pruning is undesirable or impossible, you may destroy the tents by hand. To destroy the web, use a long pole or a high-pressure water hose, especially in hard-to-reach areas.
- If pruning is possible, or isn’t sufficient, use an organic spray containing Spinosad such as Fertilome Borer, Bagworm, Tent Caterpillar and Leafminer Spray. Spinosad is selective in that it mainly targets caterpillars and is relatively harmless to other insects, fish, birds and warm-blooded mammals.
- Other organic sprays include those containing BT, a biological control.
- Carbaryl is a chemical spray that is also effective.