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Plant NameTypeDescription 
Oil discoloration of foliageSpruceDiseaseOil discoloration of spruce foliage is suspected when trees which normally have blue-green needles instead have bright green needles. Use of spray oils (to control insects, for instance) can permanently remove the waxy coating which gives the tree its blue color, allowing the underlying green of the needles to show through. The distribution of the discolored needles on the tree may be spotty. There is no harm to the tree; however, some aesthetic value may be lost. Growth occurring after the oil application will be blue.
Rhizosphaera needle castSpruceDiseaseThe first symptoms occur in late summer, when a yellow mottling develops on the current season's needles. During the fall to early spring, the infected needles turn brown or purplish brown. The needles are usually dropped later that spring or in the following summer. Tiny black fruiting bodies are formed in rows on the underside of the affected needles in the spring and occasionally at other times. This disease can cause severe needle loss.
RustSpruceDiseaseSpruce rusts are fungal diseases that sometimes require an alternate host to complete their life cycle. There are many rust diseases of spruce, each with different alternate hosts. One spruce rust causes witches' brooms, or abnormally bushy growth of the branches. These witches' brooms gradually lose their healthy green color and turn yellowish or brownish as the fungus matures. Kinnikinnick is the alternate host.
ConewormsSpruceInsectConeworms attack the green cones of spruce by burrowing into them and feeding. They may also bore into shoot tips, causing tip dieback, or feed on the soft bark of young growth. The coneworms are small and creamy or light brown in color with a darker head. The adult coneworm is a mottled gray moth. Coneworms also attack pines, hemlocks, true firs, and Douglas fir.
Cooley spruce gall adelgidSpruceInsectThis aphid-like insect feeds at the base of newly growing needles. The plant responds to adelgid feeding by forming a green or purplish cone-shaped gall around them. This 1/2" to 3" gall turns brown and woody by midsummer or fall and the branch tips usually die. Overwintering adelgids appear as woolly clumps at the base of buds in fall, winter, and early spring. Cooley spruce gall adelgids also infest Douglas fir, but do not form galls on that plant.
Douglas fir tussock mothSpruceInsectDouglas fir tussock moth larvae are distinguished by three long tufts of black hairs on their body (two in front, one in back) and lighter tufts along their back. They feed on the needles of spruce, Douglas fir, and true firs. On trees grown in the open, the larvae start at the top and work down, feeding mainly on the new foliage. Tussock moth outbreaks are sporadic. The hairs from tussock moth caterpillars break off easily and may irritate the skin.
Pine needle scaleSpruceInsectPine needle scale occurs on the needles of spruce, pine, and true fir. The elongate, flattened scales are white and about 1/16" long. Infested needles are mottled yellow at first, then turn completely yellow and finally brown. Light infestations cause little damage. In heavy infestations the tree may appear "flocked" or "frosted". Severe attacks by pine needle scale may kill branches or the whole tree.
Spruce aphidSpruceInsectPlants affected by spruce aphid first show yellowish blotches on the needles, sometimes with honeydew (sticky material excreted by the aphids) present. The needles may turn completely yellow or brown and drop. Spruce aphids feed during the winter and early spring, before new growth occurs, so affected trees may have needles only on the tips of branches later in the year. Damage is usually not apparent until after aphids have left the tree. Check weekly for aphids on important trees starting about November (monitor less important trees beginning around February, depending on weather).
Spruce bud scaleSpruceInsectSpruce bud scales are reddish to brown in color and occur at the base of new shoots. They tend to be very inconspicuous, as they may be partly hidden by the bark. Lower branches are often heavily infested and may be killed, while upper branches are much less affected. Spruce bud scales produce large amounts of honeydew which is often covered with black sooty mold.
Spruce budwormSpruceInsectThese larvae feed on the buds and foliage and may tie shoot tips together with webbing to make a nest. They are typically green to brown in color with a darker head and grow to approximately 1" long. The adult is a dark gray moth. This insect is an infrequent pest in the landscape. Spruce budworms attack true firs and Douglas fir as well as spruces.
Spruce needleminerSpruceInsectThe spruce needle miner feeds on spruce needles from the inside out, starting at the base of the needle. These larvae are light greenish to brown and grow to approximately 1/2" long. Large amounts of webbing are deposited around the needles. Completely mined needles may be cut off, sometimes resulting in severe needle loss. The spruce needleminer attacks mainly blue, Sitka, and Engelmann spruce in the western U.S. The adult is a small brown moth.
Spruce spider miteSpruceInsectThe presence of spruce spider mites is indicated by yellow stippling near the needle bases, usually on the lower branches and spreading upwards as the mite population increases. Damaged needles may turn reddish-brown. Fine webbing may cover the needles and twigs. The actual spider mites are very small and vary in color from greenish to orange, dark green, or black, with orange legs. These mites are often worst on dusty roadside trees.
White pine weevilSpruceInsectThe white pine weevil attacks the terminal or top shoot of the tree. Infested terminals may be seriously damaged or killed. Often, the terminal droops, wilts, or is deformed by the feeding of weevil larvae. As much as one or two feet of terminal may be destroyed, ruining the shape of the tree. Adult beetles emerge in late summer (around mid-August into fall) and overwinter in organic debris on the ground.