Identification

• Spruce budworms are the larvae of moths. The mature larvae are 1-inch-long caterpillars that are olive-brown to reddish-brown with dark-colored heads and pairs of white spots on each body segment. The adult moths have a 1-inch-wide wingspan with light-tan hind-wings and brown to brownish-orange forewings. The larvae spend the winter in cocoon-like silky shelters on the tree bark, emerging in spring when new growth begins on the trees. The budworm larvae then pupate and the adult moths emerge in mid-to-late summer.
  
  

Significance

• Spruce budworms feed on new needles and buds during spring, causing defoliation of the spruce tree, along with twig and branch dieback. The infested tree may suffer death of its top canopy as well. You might notice deformed shoots, damaged or destroyed cones and seeds, and even complete defoliation of the new needle growth. In some severe infestations, the budworms can kill the entire tree. Spruce budworm infestations tend to make trees more susceptible to bark beetle infestations, which further weaken the trees.
  
  

Insecticides

• You have several insecticide options if you want to control spruce budworms on valuable trees. Pesticides containing carbaryl are most often used to control budworms. Insecticides sold under the brand names of Dursban, Sevin and Tempo 2 are all effective in controlling budworms on spruce trees. If you want to use a less-toxic pesticide, you can try Bacillus thuringiensis, which is a biological control for many types of caterpillars, including spruce budworms. For the most-effective control, apply insecticide to your spruce tree while the buds are beginning to open, or within the two to three weeks following bud break and before the budworm larvae switch from feeding on the needles to the buds. This is typically right after the budworm larvae hatch from the eggs. You can make insecticide applications in June and July to control the larvae. Follow the instructions on the insecticide label carefully.
  
  

Control

• Other non-chemical control methods are also effective in reducing the budworm populations on your spruce trees. For example, you should trim back and discard all infested foliage on your spruce tree, as well as provide proper watering, fertilization and pruning to keep the tree healthy. You can also look for budworm egg masses on the spruce tree's bark and scrape the eggs into a pail of soapy water.