Spruces are evergreen, coniferous trees characterized by their conical form and towering heights. Spruce trees may be found in temperate regions at heights of up to 200 feet, though they can also be grown indoors as small potted plants. Like any other tree, spruce trees are susceptible to a range of pests. Pest infestations should be identified and treated early to prevent serious damage from occurring later on.
Spruce trees are susceptible to a wide range of pests, including aphids, armored scale, bark beetles and mealy bugs. Aphids are white, red, brown or green and are often seen in dense groups. Bark beetles tend to be darkly-colored, and are about the size of a grain of rice. Scale can be difficult to identify, but often appears as a bumpy, scale-like patch on branches of the tree. Mealybugs are oval and usually a white or yellowish color, sometimes with a thin, long tail.
Spruce trees may show a range of symptoms when infested by insects. Armored scales can cause tree bark to crack and secrete a gum-like substance, while bark beetles leave small holes throughout the branches and trunk of the tree. If your spruce tree loses its needles, mealy bugs may be to blame. Aphids attack new growth, which may result in stunted branches on smaller trees.
Some pests are merely a nuisance, while others can cause lasting harm. Aphids are rarely able to cause serious damage on a tree, and are often picked off naturally by other insect predators. Most species of bark beetles won't kill a tree on their own, but they can speed up a tree's decline by affecting its overall health. Armored scales are cause for alarm, as they can cause the death of new trees after a few years of vigorous feeding.
A healthy tree is much less likely to be attacked by pests than a tree that has been weakened by drought or other environmental factors. Generally, spruce trees prefer a moist, well-draining soil that's neutral to acidic. Spruce trees grow naturally in temperate regions and will suffer if grown in hot, arid zones. A sterilized commercial potting soil, rather than the potentially insect-infested soil from the garden, will help protect indoor spruces.
Bark beetles are difficult to remove from spruce trees because they burrow deep within the tree, making them hard to reach with insecticides. If your tree has a mild infestation of bark beetles or scale, you may simply want to prune off pest-covered branches and dispose of them. Sometimes pests such as mealybugs can be sprayed off the tree with a jet of water. Biological predators such as lacewings or parasitic wasps will feed on spruce pests such as scale.