Pine and Spruce Insects

Bark Beetles

There are numerous beetles that attack bark on trees and thus are categorized as bark beetles. Most are there because the bark is dead but others can be very destructive to weakened or stressed trees. The stresses can be due to a wide range of conditions such as weather related, mechanical injury, chemical injury, aging, growing site and planting. The over-wintering stage can be larvae, pupae or adults. Adults lay eggs in galleries that are mostly in the phloem but a few lay eggs in the xylem. The first beetles attacking a tree often give off a strong scent that attracts other beetles to invade the tree. The eggs hatch, larvae feed then pupate. Adults eventually emerge to start the cycle all over. Depending on the bark beetle and area of the country, there is from one to six generations per growing season.

Control is to minimize stress factors on the tree. Keep trees healthy, remove infested branches or trees (bark beetles will attack healthy pines next to dying pines so remove dying trees promptly) and destroy infected material by chipping burying or burning (where legal).

Pine Sawfly

Sawflies are non-stinging wasps that have their ovipositor serrated like a saw. The "saw" is used in making slits in the plant. Eggs are then deposited in the slit. The redheaded pine sawfly (Neodiprion lecontei) over-winters in a prepupal stage in the litter under the tree. In the spring after completing pupation, the adults emerge. Eggs are laid in slits in the edge of needles. The larvae feed on the foliage. At first the small larvae eat only the outer layer of the needles.

The white pine sawfly also feeds in the spring. It primarily attacks Eastern white pine, but will also attack other pines. Its life cycle is similar to the redheaded pine sawfly except that there is no second generation later in the growing season.

As they grow larger, the entire needle is eaten. After four weeks the sawflies fall to the ground to spin a cocoon. There is usually a second generation later in the growing season. Mice (eat the pupae) and diseases often cause the populations of this sawfly to crash. The European pine sawfly (Neodiprion sertifer) is found in large numbers and "waves" in mass as a means of scaring off predators. It feeds on mugo pines as well as many other pines. This sawfly larva feeds for about six weeks. They feed on older mature leaves, leaving the emerging needle alone.

Failure to control the European Pine Sawfly insect is not usually fatal to the plant. However, a more sparse plant will be the result. However, redheaded and white pine sawflies can kill branches or the entire tree if numerous. If an insecticide is applied, it is best done when larvae are hatching or very small to minimize damage. Time to treat often corresponds to saucer magnolia petal drop. Control as soon after egg hatch as possible. Check with your local land grant university (Cooperative) Extension Service for recommended insecticide.

European Pine Shoot Moth & Nantucket Pine Tip Moth

The European Pine shoot moth attacks red, mugo, Scots, Austrian, ponderosa and a several other pines. The beetle kills the tips of the branches – terminal and laterals. There is one generation per growing season. Eggs are laid at the base of new needles in late spring. After hatching, the insect mines the base of the needle. The insect tunnels into the shoot from the base of a needle. The needle usually dies and turns brown during the summer. By the middle of summer, the insect has moved into the new buds. By late summer the insect stops feeding. European pine shoot moth tends to over-winter in the injured tissue Severe infestation may give the infected tree a reddish appearance. Severe infestation on small trees may cause their death. This insect is more of a problem in Christmas tree farms and in commercial tree nurseries then in the home landscape. Drought and poor growing conditions seem to increase damage by this shoot moth.

The Nantucket pine tip moth attacks all pines with two or three needles per bundle except for two of these pines not normally grown in the midwest. This insect usually has several generations per growing season.

Prune out and destroy the dead branch tips. Check with your local land grant university (Cooperative) Extension Service for the recommended insecticide.

Zimmerman Pine Moth

Zimmerman pine moth is the insect that causes the pitch/sap to occur on the upper side of the branch crotch. When feeding damage is severe at all the crotches at a particular whorl of branches, the trunk may break off at that whorl.

Prune out damaged wood. Check with your local land grant university (Cooperative) Extension Service for the recommended insecticide. Control may be done in spring when saucer magnolia is in pink bud to early bloom or in mid to late summer when panicle hydrangea is pink.

Yellow Belly Sapsucker

Even though the Yellowbelly Sapsucker is not an insect, but a bird, its damage is sometimes confused with Zimmerman pine moth or canker diseases. The sapsucker makes feeding holes in line patterns (one or more lines of holes, several holes to many holes per line, lines may be across or up and down or on an angle). The holes are made on the trunk between the branch whorls and not at the whorls. The location separates the bird from Zimmerman and the holes separates it from canker diseases. Pitch often accumulates over these holes after the bird leaves. The bird is protected.

Place an inflated snake near the affected area in the tree during migration. This can help reduce additional damage.

Pine Bark Adelgids

Pine bark adlegids (Pineus strobi) are often referred to as bark aphids. Of all the pines in the Midwest, eastern white pine seems to be the one most often attacked. Light infestations do not do much to the tree. However persistent severely heavy yearly attacks can cause some stunting and possible death of the trees.

The adelgids produce a wax while feeding. The wax is a protective cover that resembles wool, making them look like wooly aphids to which they are related. Under this waxy wool the adelgid is teardrop shaped and black in color.

Insecticides can be used to control these insects. Check with your local land grant university (Cooperative) Extension Service for recommended insecticide. Apply in May or later when adelgids are present. In the spring use a spreader – sticker in insecticide application.

Pine Needle Scale

Pine needle scale (Phenacaspis pinifoliae) attacks mugo, Scots, Austrian and red pines. Landscape trees, Christmas trees and trees along dusty roads are the most seriously affected trees. As the number of insects increase the tree often looks like it has been "flocked" in the summer. In addition the amount of damage increases. Left alone, the insects will kill the tree. Pine needle scale over-winters as reddish eggs under the dead female body cover. Eggs hatch during candle growth. The crawlers move onto the new needles on the same tree or they may be carried or blown onto another tree. In the midwest, one life cycle occurs per year. In other parts of the country, two life cycles may occur in one growing season.

Correct timing of insecticidal sprays can eliminate this insect. Check with your local land grant university (Cooperative) Extension Service for recommended insecticide.

Pine Tortoise Scale

Pine tortoise scale (Toumeyella parvicrnis) attacks mainly Scots and jack pine. It can also be found on Austrian and red pines. Crawlers occur in late June and July. Heavy feeding by this insect on pines produces sufficient honeydew for the sooty mold fungi to grow on. Sooty mold will turn the plant black. The adult female may produce 500 crawlers. The adult males can fly but not feed. This scale has only one generation per year and prefers young trees to older trees.

Check with your local land grant university (Cooperative) Extension Service for recommended insecticide. Spray when Vanhoutte spirea is blooming. Second spray needed when hills of snow hydrangea blooms are turning from white to green and a third spray 7 to 10 days after the 2nd spray. A summer oil may discolor the needles.

Pales Weevil, Root Collar Weevil, Root Collar Weevil

Pales Weevil (Hylobius pales) is a serious pest in southern Illinois and in the south especially in nurseries, Christmas tree farms and forests. They feed on pine and spruce as well as many other conifers. This insect seldom bothers landscapes since there is very little breeding material left around. The adult chews small holes in the bark of small twigs and branches. Bark may fall away in the chewed areas. On large trees the chewing is usually near the end of branches. Needles and shoot beyond the chewed area often die, leaving reddish dead tips, which is considered unsightly. The adults feed at night and hide in the leaf litter during daylight. They over-winter as adults and emerge from late April to June depending on location. Adults may survive more than one "season" (fall through the following fall). It is not uncommon that they survive two "seasons. Adults lay their eggs in the roots of fresh cut stumps of pine trees. Larvae feed in the roots for most of the summer. They emerge in the fall after pupating in the roots of the cut trees.

Northern pine weevil has a similar life cycle to pales weevil except that the larva feeds under the bark of the aboveground stump portion. It causes the same type of damage as pales weevil.

Root collar weevil has a life cycle similar to pales weevil. However, root collar weevil larvae feed under the bark at and below the soil line on living trees, causing the tree foliage to yellow and die. Adults cause the same type of damage as pales weevil.

Grind out the stumps of cut down conifers for pales weevil and northern pine weevil. Spray base of tree in mid May and mid August for pine root collar weevil. Remove debris from around the trunk before spraying. Check with your local land grant university (Cooperative) Extension Service for recommended insecticide.

Pitch Mass Borer

Pine pitch moth adults resemble yellowjackets. The adults are clear wing moths. There are many types of pitch moths. All are in one genus – Synanthedon sp. Single eggs are laid on the bark of the pines. Larvae of some species tunnel into the cambium area soon after hatching. They make a hole in which they feed. Sap oozes out of these pits/holes. The pitch mass borer (Synanthedon pini) attacks Austrian, eastern white, Scots and Jack pines as well as white, Norway and Colorado blue spruce. Adults are only seen during the summer and the insect can take up to three years to complete its life cycle.

Check with your local land grant university (Cooperative) Extension Service for recommended insecticide.

Gypsy Moth

Gypsy moth (Lymantria dispar) feed on a wide range of plants including pines and spruces. When the hosts are present and the infestation is light, gypsy moth prefer to feed on alder, hawthorn, lindens, oaks (the most preferred tree), poplars and willows. As infestation is increased, black gum, elms, hickories, maples and sassafras are eaten. When infestations are at peak levels, the larvae also feed on arborvitae, beech, hemlock, pines and spruce. Larvae seldom if ever feed on ash, balsam fir, catalpa dogwoods, holly, junipers, sycamores, tuliptree, and trees in the Juglans genus. Conifers are usually killed by one severe year of heavy feeding. Deciduous trees can usually tolerate several years of severe feeding before declining and possibly dying, The adult male is brownish and the adult female is whitish. The male can fly but the female in the midwest populations cannot.

The egg mass is about the size of a silver dollar and is light brown (tan). The eggs are laid whereever the female feels like leaving them (in car wheel wells, in side swing sets & gutters, sides of houses & trees, and so on). Eggs hatch in Northern Illinois about mid-May. The larvae climb from where the eggs were laid on and spin a silk thread. Using the wind they may be carried several hundred feet to several miles. The larvae are covered with hairs that irritate many predators and sometimes, humans may even develop irritations from the hairs. When infestations are light the larvae feed mostly at night. When infestation are heavy the larvae may feed continuously. After about 6 to 7 weeks, the larvae are ready to pupate. The larvae leave the trees to find a sheltered area. Adults begin to emerge in July. Usually the males are out several days before the females. Males can detect females as far as a mile away. The adults do not feed but die soon after mating and laying eggs.

Spray with Bacillus thuringiensis 'Kurstaki' (considered "organic") or check with your local land grant university (Cooperative) Extension Service for a recommended insecticide.

Spruce Mite

Spruce Spider mite (Oligonychus ununguis) is not an insect. It has eight legs and is thus considered an "insect relative". It feeds on pine, spruce and many other needled evergreens. Thin silk strands may be found due to mite infestation. Stippling – the tiny yellow to whitish spots due to feeding, may cause the needles to die and turn reddish brown when infestations are severe. Spruce mites, feeding in the spring when temperatures are cool, tend to return in the fall in higher numbers. At first young mites (larvae) have six legs but after one molt they have eight legs. The adult mites tend to be green but can be brown. Spruce mites use the wind and their silk strands to disperse.

Reduce stress on trees. Use a sheet of white paper to check for mites starting when saucer magnolia is in pink bud to early bloom. Shake or rap the spruce branch on the paper. If tiny green to brown slow moving "dust particles" are seen a miticide may need to be applied Spruce mites leave a green streak or blotch when crushed. DO NOT use an insecticide. Insecticides tend to increase a mite problem by killing off the predatory mites. Check with your local land grant university (Cooperative) Extension Service for recommended miticide.

Spruce Gall Adelgids

There are two spruce gall adelgids. One is the Cooley and the other is the eastern. The Cooley spruce gall adelgid (Adelges cooleyi) attacks Siika, Oriental, and Colorado blue spruce and Douglas fir. The immature female over-winters becoming mature in the spring. She lays several hundred eggs on side branches. After the eggs hatch, the young migrate to the base of needles on the new growth. The feeding induces the plant to envelop the individual adelgids as a group thus forming a gall. The gall tends to go out to the tip of the shoot. The shoot may curve as a result of the gall being on only on side of the shoot. The entire new shoot may be one long gall too. By late June – July the adelgids emerge from the galls. The females become winged and fly to Douglas fir or other spruces. Several life cycles later and through most of another growing season, the adelgids return to the spruce trees. It takes two full growing seasons for the adelgids to make one complete cycle between both hosts.

On the spruce, galls are evident. On the fir, there is no gall but severe infestation does cause yellow spots to appear on the needles. Eastern spruce gall adelgids (Adelges abietis) attacks mainly Norway spruce but can be found on Colorado blue, white, and red spruces. In the Chicago area, they are found more often on Colorado blue spruce. Over-wintering as immature females, the females mature in the spring and lay between 100 and 200 eggs next to buds ready to open. The young feed on needles and eventually move to the base of the needles. A gall develops. The gall looks like a tiny pineapple near the base of the shoot. After leaving the galls in late June – early July, they become mature flying females. She lays her eggs in unprotected masses near the tips of needles. The cycle then starts again.

Check with your local land grant university (Cooperative) Extension Service for recommended insecticide. Apply insecticide in late September or in spring just before bud break. Dormant or summer oils will turn "blue" spruces green till the following year when new growth emerges.

Spruce Needle Miners

There are several species of needle miners. Spruce needle miner (Endothenia albolineana) attacks most types of spruces. Eggs are laid like shingles on the spruce needles. After hatching the larva enters the base of the needle, hollowing it out. The larvae cut the needles off after completely mining them. Dense mats of silk threads hold the dead needles on the twig. Larvae feed on one needle after another till fall. At this time, the larvae over-winter inside a needle. They emerge in the spring and feed till they pupate.

Apply an insecticide in early spring. Check with your local land grant university (Cooperative) Extension Service for recommended insecticide.

Spruce Bud Scale

Spruce bud scale (Physokermes piceae) attacks mainly Norway spruce but it will attack other spruces. This scale is small and is often clustered in-groups of 3 to 8 at the base of new shoots. Their size and color often allows them to be over looked or mistaken as buds. They are round and reddish-brown in color. Lower branches are more often attacked than higher branches. Severe infestations can produce sufficient honeydew to develop so that sooty mold will grow. In addition severe infestations can cause lower branches to die especially on trees that are already weak or stressed. There is only one generation per growing season. The immatures over-winter on the under side of the needles. In the spring the females move onto the twigs to complete their development. Crawlers usually appear in June.

Check with your local land grant university (Cooperative) Extension Service for recommended insecticide. Apply when hills-of-snow hydrangea is in bloom. Summer oils will turn blue spruces green.

Written by James Schuster, Extension Educator, Horticulture, and reviewed by Dr. Phil Nixon Extension State Specialist, Entomology, University of Illinois at Urbana-Champaign.