Identification

• Caterpillars are often found feeding on willow leaves. A single attack will not usually kill trees, but repeated attacks that cause the tree to become defoliated can increase the likelihood of other pests and diseases. Poplar tentmakers are most often found on willows and poplars. Trees growing in open areas are more likely to be attacked by this pest, and feeding can completely defoliate infested trees. Poplar tentmakers are light brown or black and measure up to 42 mm in length. Four yellow lines are visible on their back, which are bright in color. Adult forms of poplar tentmakers are grayish colored moths that do not damage willow trees.
  
  

Symptoms

• Willow trees infested with poplar tentmakers or other defoliating caterpillars typically have leaves that appear skeletonized or lace-like from the feeding of newly hatched larvae. As the larvae grows, it consumes more and more leaf tissue and can completely consume entire leaves. Large tents may be seen on infested trees where they eggs stay until hatching. Each adult moth lays 150 to 300 eggs in each tent. Heavy infestations of these caterpillars can cause willow trees to weaken over time. Repeated defoliation can kill willow trees under stress from drought or injury.
  
  

Cultural Control Methods

• A variety of predatory insects feed on caterpillars and their eggs, keeping their populations low. Viruses and diseases also help control these pests. If just a few caterpillars are feeding on your tree, remove them by hand and place them in a bucket of soapy water to kill them. Remove and destroy tents with eggs inside, as well.
  
  

Chemical Control Methods

• Willow trees that are heavily infested with defoliating caterpillars may require chemical treatment to prevent further damage. There are a variety of products labeled for use on caterpillars. Many products contain powerful active ingredients such as acephate, bifenthrin or cyfluthrin. Most chemical control products work best when applied while caterpillars are small.