Spruce budworm is a very serious pest in our area and can be found in all species of spruce. The adult moths will lay their eggs in July and early August. These adults will lay approximately 100-150 eggs in a cluster pattern. Each cluster usually contains 15-40 eggs and can be found on the underside of the needles of a spruce tree. After a 2 week period the larvae appear and start to prepare for the upcoming winter season by building nests made out of silk.

These larvae do no damage to the tree at this time. Their goal is to survive the winter to feast on the new growth of your tree in the spring. As the trees begin to bud in the spring the larvae begin by feeding on the old growth. Once the tree has fully budded, the larvae move to this new succulent growth and feed for 4-5 weeks. You can identify spruce budworm larvae by their reddish brown bodies with yellow spots. Their heads are shiny and are dark brown in colouration. After their larval stage the budworm pupates within the tree and emerges as an adult moth in about 10-15 days. Only one generation of spruce budworm occurs every year.

Damage:

By feeding initially on the old growth spruce budworm will do little damage to your tree. However, once the larvae move on to the new growth, they will form nests and feed continually on this new growth. You can identify damage caused by this pest by observing a reddish brown, almost scorched look to the crown or top of your trees. The larvae are inefficient consumers and will often leave partially consumed needles. If your trees have a bad infestation, the larvae can consume all of the new growth on your tree. If this infestation continues for 4-5 years the larvae are capable of killing the entire tree.

Controlling the problem:

Ordinarily natural factors such as predators and weather are enough to control spruce budworm populations. Occasionally these populations will explode and require a different means of control. If at all possible you can pick the larvae off your trees by hand. Ensure this is done early in the spring. Encourage birds that feed on insects such as jays to live near your home. If you are using an insecticide, ensure you follow all the directions on the label before and during applications. Wear appropriate clothing when applying.

Paul is a Certified Pesticide Applicator in the province of Alberta, Canada. He has over 15 years experience in the lawn care industry.

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