Mimosa Webworms are Showing up on Locust Trees

Compliments of the Bellevue Tree Board:

Mimosa webworms are beginning to show up on locust trees across the Omaha area.

These small, gray-green caterpillars are the larvae of a moth and feed in groups on the outermost tips of branches. As they feed, they spin dense, silken webs that enclose the foliage and serve as both shelter and feeding zones. This webbing is water-resistant, which makes it challenging for many insecticides to penetrate effectively. Their feeding can lead to browned, skeletonized leaves, causing unsightly damage that may be mistaken for environmental stress or other pests. While this damage is mostly cosmetic, repeated infestations can reduce a tree’s overall vigor.

Although it may be tempting to prune out the webbed areas, doing so often causes more harm than good, especially if large sections of the canopy are affected. Instead, it’s best to work with a certified arborist who can assess the extent of the infestation and recommend appropriate management strategies. This might include the timing of treatments targeting young larvae before the webbing becomes too thick. In our region, mimosa webworms typically produce two generations per growing season, so addressing the first generation early can help reduce the impact of the second. As always, keeping trees healthy through proper watering and care can also improve their resilience to pests.