My Japanese maple tree is covered in catapillers (photo attached). They are...

Asked September 3, 2019, 5:06 PM EDT

My Japanese maple tree is covered in catapillers (photo attached). They are devouring the leaves and making cocoons. Also spreading to other plants like hostas, lilies and other trees. What is it and how do we destroy it? And prevent it on other trees/plants not yet affected? Thank you.

Auglaize County Ohio trees and shrubs insect issues insect identification trees definite marked tussock moth

3 Responses

This is a Definite Tussock Moth Caterpillar (Orgyia definite). If your maple is mature, this late in the season the caterpillar damage, although unsightly, shouldn’t negatively impact the health of your tree next year as outbreaks are generally limited to 1 year.

The attached article discusses the White Tussock Moth Caterpillar although it mentions the Definite Tussock Moth Caterpillar at the end. The information applies to both. Please heed the warning to wear protective clothing if you’re going to handle the caterpillars! If you choose to use a chemical control, read and follow all label directions.

https://bygl.osu.edu/node/1324

Thank you. Can Seven powder be sprinkled all over the tree or Seven spray, without killing the tree? I'm not at all familiar with the scientific products you mentioned.

As Bridget had mentioned in her earlier response, it is too late in the season to be worried about killing the caterpillars, especially those that have already spun a cocoon. The products that were mentioned in the BYGL article, (i.e. synthetic pyrethroids are very common active ingredients in many insecticide products sold to homeowners. Most of these products end with -thrin such as permethrin, resmethrin, delta-methrin and gamma-cyhalothrin. Names such as these will be found under the Active Ingredient portion of a product label (e.g. Spectracide's Triazicide Insect Killer contains Gamma-Cyhalothrin). For any product that you are thinking of using, read the label of the product to see if it can be used on a Japanese Maple tree. Some plants are very sensitive to pesticide products.

A slight correction to Bridget's earlier response, the caterpillar is not a definite tussock moth. It is the white-marked tussock moth caterpillar.

As to whether the moth will be a problem again next year, one can only wait and see.