What’s Up With That? Webworm’s gauzy nest in trees no cause for worry



Every day on my way to work, I drive down Ward Road and pass rows of plum trees. Recently, I’ve noticed some of the trees have these white nests wrapped around the branches. What are those and what are they doing there? Should I be concerned?

— Concerned Commuter

Never fear, C.C., those gauzy nests are created by a pest common to the Pacific Northwest called the fall webworm.

“People see them and think the sky is falling. Well, the sky is not falling,” said Charles Brun, horticulture adviser at Washington State University Vancouver. “It’s really no big deal.”

During the larval stage these worms, or caterpillars actually, congregate on the tree and ensnare a branch and its leaves in a big, gauzy tent.

Although the worms defoliate part of the tree, a tree can withstand multiple attacks without any lasting damage. So, other than being creepy, they’re relatively harmless. Brun says the minimal damage they create is not worth using pesticides.

“This is a great story on our patience or tolerance,” he adds.

This time next year, it will be as though nothing ever touched those beautiful thundercloud flowering plum trees.

If you want something to worry about, then you’ll have to look at our area’s history. Clark County is no stranger to a much more destructive pest, called the gypsy moth. Each year, the county sets more than 1,000 traps to capture a pest that threatens to turn the Evergreen State brown. The moths devour leaves and are capable of weakening and killing large numbers of trees.

An incursion of those would be considered a 10 out of 10, Brun said, while the webworm doesn’t even register a one on the worry scale. Gypsy moths, luckily, have not been a problem locally for many years.

One way to tell the difference is that gypsy moths get busy in spring while webworms do their thing in late summer to early fall.

— Patty Hastings

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