Weeping Willow Infested With Worms

A mixture of sap and excrement will often flow from the holes in the tree's bark.

A wood boring worm-like caterpillar, the carpenter worm (Prionoxystus robiniae) can cause significant damage on weeping willows and other tree species, according to the University of California. The weeping willow's propensity to grow near ponds makes it more susceptible to the carpenter worm, because the insects frequent riparian areas.

Identification

An adult carpenter worm appears as mottled black and gray moth that can measure up to 3 inches in width. The hind wings of the female moth are white and the male's hind wings are orange. The light green worm-like larvae of the moth measure up to 3 inches in length and 1/2 inch in diameter.

Damage

In spring, the female lays up to 200 eggs in the willow tree's bark crevices. When the larvae hatch, they burrow into the wood. The worm-like larvae will reach the heartwood within four months of burrowing, according to Utah State University.

Control

Dead areas of bark will result and may fall from the tree. The insects weaken the willow tree and make it susceptible to wind damage. Injectable insecticides can help control the larvae. Spraying the tree with insecticides before the larvae enter the bark will also help control the pests.

References

• University of California: Carpenter Worm
• University of California: Willow
• U.S. Forest Service: Carpenter Worm
• Utah State University: Carpenter Worm

Resources

• Washington State University: Carpenter Worm