ID Horde of Caterpillars on Japanese Maple

Asked August 19, 2017, 6:50 PM EDT

I like assistance with identification of a pest that was found on a Japanese Maple tree about a week ago. Name, age and/or size of plant Japanese Maple, We've enjoyed the tree for 14 years so we've assumed that it was planted by the first homeowner's which would make the tree about 40 - 50 years old; about 20 - 25 ft tall. It's a very healthy tree with foliage that turns to bright yellow during the third to fourth week of October every year. When was the problem was first noted? August 13, 2017; The problem was isolated on two small branches. What part of the plant is affected? Two small branches with a diameter of about 1cm each. When I noticed the "spider web-like" tent, I pruned the tree of the tent before taking pictures. Afterwards, I noticed several white caterpillars that appeared to be feeding, so I quickly snapped a couple of pictures and then cut off the small branch to both remove and isolated the caterpillars. The affected area was very small with no other visible infestation since 8/13/2017. From the white appearance of the caterpillars they do not appear to be gypsy moth caterpillars or tent caterpillars. Could I be wrong?

Montgomery County Maryland

1 Response

These are fall webworms. Unlike the tent caterpillars we see in spring, these caterpillars construct their webs at the tips of branches. You do not have to prune off the webs. You can put on gardening gloves and scape them off, plus the caterpillars, and place in a bucket of soapy water.

These are native insects and provide food for a host of birds and other wildlife. Because they start munching late in the season, they do not kill trees, which have already had plenty of time of produce carbohydrates for the year. (Possible exception would be a new sapling--but they don't usually get on those.)

Here is our webpage about them:

You don't have to take any measures.