by: Karen Ripley, DNR Forest Health Program Manager
Another insect that causes concern to landowners this time of year is the silver spotted tiger moth (Lophocampa argentata). These colonial caterpillars make somewhat unsightly nests in the upper branches of conifer trees. The nests become very obvious in April and early May.
This photo shows a colony of the silver spotted tiger moths taken in Everett, Washington earlier this week. This cluster of hairy caterpillars and their protective silken nest is normal and not to be of concern. Although the nests reach their largest sizes in early spring and can be somewhat unsightly, they don’t damage the host trees much at all. These insects affect only a tiny percentage of a tree’s foliage and the caterpillars are only consuming the older needles, which are less valuable to the tree than younger needles. By the time tree buds break and new needles emerge at the ends of the twigs during May, although these portions of the branches might be stripped bare of old needles, the tiger moth caterpillars will have wandered away from this site to make their cocoons.
In fact, a high percentage of these caterpillars are actually not going to mature. They’ve already been parasitized by wasps and flies- and sort of serve as nature’s reservoir of beneficial insects over the winter. Do not make a special effort to destroy these nests. It’s not worth the time and would deny your area of the beneficial insects that have parasitized these caterpillars are currently maturing within their bodies. (And these beneficial parasites are really important to kill tent caterpillars, another native caterpillar that’s been revving into outbreak status in the Everett area in the last year or so.)
If you want to learn more on the silver spotted moth a good article on this insect can be read by clicking here.