Spruce budworm is a highly destructive forest insect pest that lives throughout the northern United States and southern Canada. It is a small gray-brown moth with dark markings. During its caterpillar stage, it feeds on the needles of spruce and fir trees.
Female moths lay their eggs on spruce and fir trees in summer. The eggs hatch into caterpillars, which spend winter on the trees. In spring, they begin to eat the new tree buds. The caterpillars spin cocoons in summer and emerge as moths. Spruce budworms can kill a tree by eating its needles for three to six years.
The number of spruce budworms has been controlled naturally by the insect’s limited food supply and by birds and other enemies. However, in the eastern United States and eastern Canada, an outbreak of spruce budworms has occurred every 30 to 60 years.
Since the 1940’s, more than 20 million acres (8 million hectares) of forests in Maine, New Brunswick, and Quebec have been sprayed at least once with pesticides to kill spruce budworms. However, pesticides only kill part of the spruce budworm population. The survivors thus have a large food supply and can reproduce in great numbers. In addition, environmentalists argue that widespread use of pesticides harms the environment. During the early 1980’s, researchers increased their efforts to control spruce budworms through forest management methods and biological controls. By the late 1980’s, outbreaks of spruce budworms in eastern North America had subsided.
