Poplar trees, Populus spp., belong to the willow family. They grow quickly in full sun, and can reach heights of 60 feet. While poplar trees are prone to many pests, according to the University of California, only one worm is a pest for the species. This worm is called the webworm, and it is mainly a problem during the fall months. Webworms can destroy your poplar tree if you do not control them.
Look for hair-covered clusters, or webs, on the underside of your poplar tree leaves. The larvae of the webworm are inside.
Put on a pair of gloves and tear the webs open. This allows natural predators of the webworm to get inside and eat the larvae.
Hit the larvae loose with a broom if the natural predators are not doing their job. Be prepared to catch the larvae with a garbage bag. You can then easily toss them out with the trash. This method will work well for smaller poplar trees, or for the lower portion of larger poplar trees.
Purchase an insecticide that contains the ingredient permethrin. Read the label to ensure it specifically lists webworms as a pest it controls.
Mix and apply the insecticide as directed on the product label. Use a hose-end sprayer to reach all parts of the tree efficiently.