Remove branch that holds tenting insects

What’s the best way to get rid of bag worms?

- Jim

This is where common names can get us into trouble as we deal with insect problems. Without a description of the worm in question, I am guessing it’s either tent caterpillars or fall webworms you are talking about. Both create a tent or baglike structure that the caterpillars live in after hatching.

Tent caterpillars used to be a problem mostly on the coast, but they are becoming more common here. They are black and yellow with hairy bodies two to three inches long. Normally they form their webs in early summer in ash, alder, apple, birch, cherry, cottonwood, willow and fruit trees and roses. The caterpillars venture out from the web to feed on nearby leaves.

Fall webworms are similar but they tend to build their nests in the late summer and early fall. The caterpillars are two to three inches long; yellowish brown with black and orange bumps and long whitish hairs. They tend to build their nest around a branch of tasty leaves and then eat everything inside the nest. As they eat up the leaves, they expand the nest to take in more branches.

Willows, cottonwoods and fruit trees are a favorite but not their only food source.

The caterpillars are more of a nuisance than anything else. They are not poisonous to people or animals and unless their numbers are extremely high, the damage they do is just an annoyance.

The easiest way to control them, if they aren’t way up in the tree, is to simply cut the branch off with the nest attached, bag them up and throw it in the trash. To remove over-wintering pupae, rake up leaves under trees where they were and throw the leaves in the trash.

A spray of the biological control Bacillus thuringiensis will control the caterpillars if sprayed around and on the nest. This is a bacteria that attacks only the caterpillars.

Late-trimmed shrubs flourishing

I trimmed some shrubs in late summer: a cotoneaster (umbrella bush) and red-stemmed dogwood. Since then they are growing like crazy. Big mistake?

- Marian and Bart

Normally shrubs should be pruned no later than mid-July to allow them to put out new growth and have a chance to harden off before winter. If you pruned them in late August, the growth may not have as much of a chance to do so if our cold weather comes quickly. Fortunately, red-twig dogwood and cotoneaster are reasonably hardy plants.

There is not much you can do at this point, though. If we get a very cold winter, you will see some dieback in the spring and maybe even later into the summer.

Cold damage on plants can show up even a couple of years later, because the plant may be successful in keeping the damaged part going until it is stressed by something else, like more cold weather or a drought.