Twigs Curled And Distorted
Aphids - Aphids are greenish, soft-bodied, pear-shaped sucking insects about the size of a pinhead. They tend to cluster on tender new growth to feed. The balsam twig aphid sucks sap from Fir twigs and causes them to curl.
Needles Discolored, Webbed Over
Spider Mites - Mites are about 1/50 inch long, barely visible to the unaided eye. Related to spiders, they have 4 pairs of legs, piercing, sucking mouth parts, and very compact bodies. They may be yellow, green, red or brown. Pale, curled Fir needles stippled with tiny yellow dots or red spots suggests spider mites. The needles are often distorted or swathed in fine webbing.
Needles and Buds Eaten Out, Defoliation
Spruce Budworms - Larvae of this small moth are among the most serious pests of needled evergreens. It lays its eggs along the Fir needles. The larvae grow to be inch-long caterpillars, brown with yellow stripes down the sides. In the spring they feed heavily on the needles and then the new buds. Then they weave messy silken webs and pupate inside. A serious infestation can defoliate the entire tree.
Small Bumps on Leaves and Stems
Scale Insects - Scale insects form groups of small bumps or blister-like outgrowths on needles and twigs. These are waxy shells that protect the insects feeding beneath. The shells may be white, yellow, or brown to black, and are about 1/10 to 2/5 inch in diameter. The First sign of a scale attack is often brown or yellow Fir needles, which draws the eye to the scale colonies feeding there. Some species excrete honeydew, which coats foliage and encourages ants and obvious sooty mold growth. Heavy infestations of scale retard tree growth and may even kill the tree.
Gypsy Moth - Gypsy moth caterpillars grow from about 1/16 inch long at hatching to about 2-1/2 inches long by the time they become pupae. Mature larvae are covered with black hairs and have 5 pairs of blue spots, 6 pairs of red spots along the back, and voracious appetites. In July, they encase themselves in brown shells to pupate. Gypsy moth larvae are often confused with the eastern tent caterpillar and fall webworm, both of which make silken tents in trees. Gypsy moths do not make tents. Seek out the distinctive sawdust-colored egg-masses on trunks, branches, under your roof eaves, and other protected spots. The eggs look like little gold pearls. Uncontrolled, gypsy moth caterpillars can defoliate a Fir tree completely. Crush egg masses or drop them into a pail of water mixed with kerosene.
Branches Hung With Tiny Fringed "Bags" [CURLY QUOTES]
Bagworms - Bagworms are dark brown caterpillars with white or yellow heads. They carry their bags with them as they feed. The small spindle-shaped bags hanging from Fir trees like Christmas ornaments are bagworm cases. Each case is woven of silk and bits of needles, and houses a caterpillar. A fully developed bag is about two inches long and protects up to 1000 eggs over the winter, which hatch out the following spring. Bagworms can kill a tree if left to themselves. During the winter, handpick the bags from your trees and burn them.
Needles and Twigs Discolored, Stunted Needle And Twig
Blight - This fungus disease causes needles to turn reddish-brown and twigs to blacken and die back, giving a seriously infested tree a scorched look. Prune and destroy affected branches.
Needles Discolored, Drop Prematurely
Needle Cast - This fungus disease causes Fir needles to turn yellow, then shrivel and drop off. Infected needles show black spore-bearing bodies on their undersides.
Girdling Lesions On Trunk and Branches
Canker - Various fungi attack trunks and branches of Firs. They cause the formation of long oval sunken areas with raised edges. These may girdle branches, or kill the entire top of the tree. Infection frequently starts where the bark or sapwood has been injured or weakened by other pests and diseases, transplant shock, or drought. Prevention is the only control for this disease. Avoid bark injuries and keep Fir trees well fed and cared for.