Dead Tree and Stem/Root Injury Title Banner
 
Dead Tree Illustration  
Dead Tree and Stem/Root Injury

Whole or most of the tree is dead or dying. Needles fade from green to yellow to red or brown and may eventually fall off. Some trees may be leaning or fallen over.

Evidence of stem injury includes masses of pitch, holes in bark, and girdling (bark removal). Your tree may be in the advanced stages of injury caused by other pests, so if you cannot find the agent here, check pests in other injury categories.


 


Allegheny Mound Ant Title Banner
Allegheny Mound Ant
Formica exsectoides Forel

Hosts: All Christmas tree species.

Importance: Mound ants kill all vegetation within 20 feet of their mounds (nests), including seedling or sapling conifers. The ants will also kill large trees that are as far away as 50 feet if those trees shade the ant mounds.

Look For:
A group of dead or dying trees. Search the bases of affected stems for symptoms of injury, such as small blister-like swellings.
A large ant mound, 1 to 3 feet high and 2 to 6 feet across, located among the injured trees.
Large ants, ¼ inch long, with either black or reddish-brown front ends and red tail ends. Look for ants on the mound or on live trees.

Pests that cause similar symptoms: Pocket gopher.

Biology: These ants kill trees that shade their mounds by injecting formic acid into the bark of the lower trunk. The ants also protect aphids and scales on live trees by discouraging the aphids’ natural enemies (parasites and predators).

Monitoring and Control: Look for mounds between trees or rows of trees in stands of all ages throughout the growing season. Treat individual mounds as soon as you find them.
• Kill adult ants by applying a registered, residual insecticide to mounds any time between mid April and October. Either level the mound with a rake before treating, or mix the insecticide into the upper 2 to 3 inches of the mound. For best results, apply just before a heavy rain. Treat again if a new mound appears. Be careful; these ants will bite.
• Keep aphid and scale populations low.

NEXT CROP
• Level and treat mounds before planting a new crop of trees.
Allegheny Mound Ant
Black dividing line
Hosts: All Christmas tree species


Armillaria Root Rot Title Banner
Armillaria Root Rot (Shoestring Root Rot)
Armillaria spp.

Host: All trees.

Importance: This fungus kills by girdling trees at the root collar. Trees under stress and trees in cutover hardwood stands are most susceptible to infection.

Look For:
Yellowing, then browning of all needles.
Resin on the bark at the root collar, where the stem and roots meet.
Creamy white, leathery sheets of fungus under the bark at the root collar.

Armillaria Root Rot Pests that cause similar symptoms: Drought, pine root collar weevil, wood borers, and bark beetles.

Biology: Black fungal strands (rhizomorphs or “shoestrings”) from infected stumps grow through the soil and infect nearby conifers.

Monitoring and Control: No active monitoring is required.
• Remove dead trees, infected stumps, and large roots.
• Reduce stress by treating for other diseases, insects, and environmental factors that damage or weaken trees. Healthy, vigorous trees are more resistant to Armillaria infection than diseased, weak ones.

NEXT CROP
• Choose a site that is well suited to the growth needs of the desired species. Avoid planting on cutover sites, especially those with many large hardwood stumps.
• If practical, remove stumps and large roots before planting.
• Maintain healthy, vigorous trees.
Black dividing line
Host: All trees


Voles Title Banner


Meadow Vole (=Meadow Mouse)
Microtus pennsylvanicus (Ord)
Pine Vole
Microtus pinetorum LeConte

Hosts: Most Christmas tree species.

Importance: Meadow voles, commonly called meadow mice, feed on bark around the base of the trunk or on lower branches, weakening trees, slowing growth, and discoloring needles. Meadow voles may kill trees by removing a complete ring of bark from the trunk (girdling). Pine voles feed on the bark of tree roots, causing short needles, yellowing of needles and slow growth. Trees may be killed or weakened, making them vulnerable to other pests.

Look For:
Active mouse runways, 2 inches wide, devoid of live vegetation. Look for runways in areas of heavy vegetation.
Piles of droppings and small caches of clipped grass.
Burrows 1 inch in diameter, 2 to 4 inches deep (meadow voles) or burrows 18 inches deep or deeper (pine voles).
MARCH TO APRIL
Girdling of the trunk near the soil line, especially on trees in heavy grass (meadow voles); girdling of the tree’s roots below the soil (pine voles).
MAY TO JULY
Lack of new developing shoots, yellowing foliage, short needles.
Completely brown trees killed by girdling.

Pests that cause similar symptoms: Rabbits, hares, and porcupines cause girdling. Scattered dead trees can be caused by pine root collar weevil, drought, or Armillaria root disease.

Biology: The meadow vole, commonly found in grassy fields, feeds mainly on grasses and other succulent vegetation throughout the growing season. The pine vole, commonly found in shrubby, weedy fields, feeds on broad-leafed plants and their seeds. During the winter when vole populations are high and normal food supplies dwindle, voles turn to eating tree bark. Feeding generally occurs below the snow line in areas of dense matted vegetation, so injury may not be discovered until the snow melts.

Monitoring and Control: Look for dead trees and injury in stands of all ages throughout the growing season. If you see voles and their runways or burrows frequently in the fall during harvest, use poison baits to protect trees. Voles often invade tree plantations from adjoining areas under the snow.
• Prune off girdled branches. Nothing can be done to save trees with girdled trunks.
• Mow close to the ground or apply herbicide around trees to destroy vole habitat.
• Apply a registered herbicide to eliminate vole cover.
• If needed, place registered poison baits in covered bait stations so song birds or other wildlife cannot reach them. Because high vole populations occur in cycles, poisoning is not needed every year.

NEXT CROP
• Remove grassy vegetation on or around site before planting and continue to control vegetation throughout the life of the trees in areas where voles are a problem.
• Encourage predators, such as hawks, owls, and snakes, to hunt voles in the plantation by providing nest boxes, hunting perches, and hibernaculums.
Voles and vole damage
Black dividing line
Hosts: Most Christmas tree species


Phytophthora Root Rot Title Banner
Phytophthora Root Rot
Phytophthora cinnamomiRands;
Phytophthora spp.

Hosts: Various species of the fungus Phytophthora are present throughout the United States and are known to infect fir, spruce, and pine trees.

Importance: Phytophthora cinnamomi is the most important species causing root rot of Fraser fir, primarily in the southeastern United States. This species requires warm, wet soil and is intolerant of temperatures below freezing. Therefore, it is not likely to become established in plantations in the Lake States and north central region. Other species of Phytophthora can survive in cold climates and are considered a threat. Infection of roots by this fungus causes root mortality and eventually can kill the whole tree.

Look For:
Foliage of seedlings or older trees changing from green to yellow to red-brown in color. All foliage on tree is likely to be affected.
Rotted and discolored roots. Root tissue may be water-soaked and soft. The root cortex (outer layer of root tissue) may easily be pulled off. Infected roots will often be some shade of red or brown. Some red-brown discoloration may also be present under the bark in the root collar region.
Stunted new growth; wilting new growth.

Biology: Phytophthora species are most common in poorly drained soils or heavier soils. This fungus produces spores that swim through free moisture in the soil. The fungus may survive in the soil as thick-walled resting spores or in dying plant material (roots) as thread-like hyphae. Seedlings with low levels of infection may leave the nursery undetected and transport this fungus to new fields. If conditions are favorable for the fungus to develop, infection will continue in the plantation and may spread to other healthy trees.

Monitoring and Control: Prevention is the key to managing this disease. Prevent introduction of Phytophthora by inspecting stock before planting. Do not plant seedlings or trees that show symptoms of Phytophthora root rot.

Action should be taken in the nursery if Phytophthora root rot is detected at any level of incidence. Inspections should be conducted regularly. A laboratory confirmation is recommended for this disease to ensure that correct management techniques are aimed at the specific fungus species.

If the site is poorly drained or has very heavy soil, consider a crop other than Christmas trees; Phytophthora and other root rot pathogens can thrive under such conditions.
Phytophthora Root Rot damage
Black dividing line
Hosts: Fir, spruce and pine


Pine Bark Adelgid
Pine Bark Adelgid
Pineus strobi (Hartig)

Hosts: Eastern white pine; occasionally Scotch and Austrian pine.

Importance: Pine bark adelgids weaken pine trees by sucking sap. Heavily infested trees grow poorly, become discolored, and lose their value. Some trees may die or become weak and susceptible to other pests during dry periods.

Look For:
Discolored, stunted, weakened, or dying trees with small but conspicuous lumps of white woolly wax on the main stem and branches. The trunk may look whitewashed.
Yellow or purplish insects, less than 1/25 inch long, under the woolly wax. Use a hand lens.
MAY TO JUNE
Dark blue-green nymphs covered with white waxy material, found in clusters on elongating shoots.

Biology: Mature females covered with woolly wax overwinter on the tree. Eggs laid in the spring produce wingless and winged forms that infest new hosts.

Monitoring and Control: Inspect trees of all ages throughout the growing season. Look for white woolly wax and blue-green nymphs early in the growing season. Treat infested trees if you notice this adelgid in any stage. Only infested trees need to be treated.

• Spray trees with a dormant oil before growth starts in the spring. Do not spray until the temperature stays above 40° F for 24 hours. Inspect the woolly wax in early May with a hand lens to make sure the insects underneath are dead.
• Or, thoroughly spray trees with a registered insecticide in mid May when the insects are active.

NEXT CROP
• Avoid planting eastern white pine, especially near Scotch and Austrian pine.
Pine Bark Adelgid damage
Black dividing line
Hosts: Eastern white pine; occasionally Scotch and Austrian pine.


Pine Root Collar Weevil Title Banner
Pine Root Collar Weevil
Hylobius radicis (Buchanan)

Hosts: Scotch, Austrian, eastern white, and red pine.

Importance: The grub-like larvae of this weevil girdle the root collar (where the stem and roots meet) and roots of young pine Christmas trees larger than ½ inch in diameter at the soil line. Complete girdling kills trees. Young trees weakened by weevils may fall over and die 1 to 4 years after being attacked. Larger trees can also be attacked.

Look For:
Yellow to red needles on entire tree. Some trees, including some with green foliage, may be leaning or fallen.
Black pitch-coated bark at the root collar and beneath the soil. Soil around tree may also be pitch-soaked.
Yellow-white legless C-shaped larvae, up to 1/3 inch long, with amber brown heads. Look for them in tunnels in the bark or in adjacent soil.
LATE JUNE TO EARLY SEPTEMBER
White pupae, up to 1/3 inch long, in the bark and soil where larvae are found.

Pests that cause similar symptoms: Scattered dead trees can be caused by vole feeding, Armillaria root rot, wood borers, or bark beetles. Pales weevil adults and pine root tip weevil adults are nearly identical to pine root collar weevil in appearance.

Biology: In the spring and summer, adult weevils lay eggs at the base of pines during the day and move onto the trees at night to feed. Weevils normally move only short distances, but will occasionally fly to other locations. The larvae feed on the inner bark of the root collar and pupate in the nearby soil. Adults emerging in late summer feed on the trees for a short time before entering the litter to overwinter. Most will live for more than 1 year.

Monitoring and Control: Begin inspecting when trees reach 1 inch in diameter at the base. If some trees are dying, treat all trees except healthy-looking ones that are ready for immediate harvest. If trees are not dying, look for injury at the base of 20 to 30 scattered trees sometime before mid May and again before mid August. Treat entire plantation if 50 percent of the inspected trees are injured.
• Prune off the lower one to three whorls of branches. This will allow more sunlight to reach the root collar area, making conditions unfavorable to weevils. Removing branches growing within 1 foot of the ground will also make it easier to treat trees with an insecticide.
• Drench the root collar and a 1 foot radius of soil around each tree with a registered insecticide during warm weather to kill adults. The best time to treat is in mid May, before the adults lay eggs. Apply again in mid August to control newly emerging weevils.

NEXT CROP
• Delay replanting of harvested areas for 1 year to deprive weevils of newly planted seedlings. If you do replant immediately or interplant with seedlings, do not plant pines.
• Do not mix pine species. Separate different pine species in the same stand by at least 100 feet. • Plant Scotch, Austrian, or red pine at least ½ mile away from weevil-infested pines.
• Plant resistant varieties of Scotch pine, particularly the short-needled varieties, such as S. French, Turkish, or others from western or southern Eurasia.
• Completely remove any adjacent older Scotch pine plantings not being used for Christmas tree production.
Pine Root Collar Weevil
Black dividing line
Hosts: Scotch, Austrian, eastern white, and red pine


Pine Wood Nematode Title Banner
Pine Wood Nematode
Bursaphelenchus xylophilus (Steiner & Buhrer) Nickle

Hosts: Pines, especially Scotch pine.

Importance: When present in large numbers, these microscopic worms can kill the pine saplings they infest. The number of trees killed by nematodes increases during periods of drought. Nematodes are often found in trees that are dying from other causes.

Look For:
Yellowing, then browning of all needles during the growing season. Brown needles remain on dead trees.
A lack of resin flowing from wounds.

Pests that cause similar symptoms: Wood borers and bark beetles.

Biology: Pine wood nematodes are spread from dead to healthy or stressed pines in the spring by long-horned beetles. Nematodes reproduce rapidly in the wood of infested trees during the summer, usually killing trees by fall.
Monitoring and Control: No active monitoring is required.
• Have a pest specialist examine the wood of a recently killed tree to determine if nematodes are present.
• Destroy infested trees by burning or chipping before beetles emerge from them in the spring.

NEXT CROP
• Avoid planting on dry sites.
Pine Wood Nematode damage
Black dividing line
Hosts: Pines, especially Scotch pine


Pocket Gopher Title Banner
Pocket Gopher
Geomys bursarius (Shaw)

Hosts: Most Christmas tree species.

Importance: Pocket gophers weaken or kill trees by feeding on their roots. Pocket gophers are found in the Great Plains area, mainly in the western half of the north central region. In the Lake States, they are rarely seen east of Wisconsin.

Look For:
Ridges in the soil caused by underground burrowing.
Semicircular mounds of soil.
Dead trees near mounds and ridges. These trees may be pulled easily from the ground and may have no roots remaining.
Destroyed tree roots.
Note that star-nosed moles also create ridges and mounds of soil, but do not harm trees.

Pests that cause similar symptoms: Allegheny mound ant, meadow vole, pine vole, thirteen-lined ground squirrel.

Biology: The pocket gopher is a burrowing rodent 5 to 8 inches long, including a short, sparsely haired tail. These animals have small eyes and ears, short necks, chisel-like teeth, and long, strong claws on their feet. Coat color ranges among species from almost white, to brown, to black. Solitary for much of their lives, they are active day and night but are seldom seen above ground. Christmas tree plantations are a favorite feeding ground for gophers because the soil is usually easy to work.
Monitoring and Control: Inspect trees of all ages in spring. Consider controlling gophers if mounds are numerous and more than 10 percent of your trees die because of injured roots.
• For small-scale problems, trap and hand-bait pocket gophers.
• For larger populations, use a burrow builder—a tractor-drawn device that digs underground runways—and bait them with poison. Drive the machine back and forth at regularly spaced intervals (about 25 feet apart) to make a series of parallel burrows that will intercept the natural gopher burrow systems. Gophers will explore these artificial tunnels and eat the poisoned bait within.
Pocket Gopher damage
Black dividing line
Hosts: Most Christmas tree species


Rabbit and Hare Title Banner
Rabbit
Sylvilagus floridanus (J.A. Allen)
Hare
Lepus americanus Erxleben

Hosts: All pines; occasionally spruce and fir.

Importance: Rabbits and hares feed on the bark and the lower branches of young pines. In large numbers, these animals can cause great damage to pine plantings. Severely injured trees may be girdled and killed or may be too damaged to be sold as Christmas trees.

Look For:
Dead or dying trees.
Exposed wood where stem and branches have been bark-stripped or girdled. Rabbits and hares will feed as high up on the stem and branches as they can reach by standing on their hind legs.
Tooth marks, 1/10 inch wide, running horizontally across the stem.
Smooth, clean, slanted cuts where rabbits have clipped off branches.
Rabbit or hare droppings and tracks near trees.

Pests that cause similar symptoms: Deer and mice.

Biology: Rabbits and hares may feed on tree bark during the winter if there is an overabundance of these animals and if their normal, preferred foods are scarce.

Monitoring and Control: Look for damage on trees of all ages in the spring, especially in areas with heavy brush (good rabbit and hare habitat). No control is needed if injury is random and infrequent. If damage is serious, check with a conservation officer or a wildlife pest control specialist to see if control is appropriate under local conditions.
• Discourage rabbits and hares by removing necessary cover, such as brush piles and bushy field borders.
• When appropriate, rabbit or hare repellent can provide good control for up to 90 days.
• Hunting can be helpful in reducing rabbit or hare populations.
• Box trapping can be effective if started in late summer and continued intensively through late winter. Contact the appropriate wildlife management agency in your state for information on hunting and trapping permits.
Rabbit and Hare damage
Black dividing line
Hosts: All pines; occasionally spruce and fir


Thirteen-Lined Ground Squirrel Title Banner
Thirteen-Lined Ground Squirrel
Spermophilus tridecemlineatus (Mitchill)

Hosts: Most Christmas tree species.

Importance: Thirteen-lined ground squirrels weaken or kill trees by burrowing along their roots.

Look For:
Burrow openings, approximately 2 inches in diameter.
Semicircular mounds of soil by burrow openings.
Dead trees near mounds and burrows.
Damaged tree roots.

Pests that cause similar symptoms: Allegheny mound ant, meadow vole, pine vole, pocket gopher.

Biology: The thirteen-lined ground squirrel is a burrowing rodent 5 to 8 inches long, including a sparsely-haired tail. These animals have short ears, short necks, and chisel-like teeth. Coat color is brown with about 13 cream-colored stripes alternately solid and spotted. They are active by day and can be seen above ground. Christmas tree plantations with grassy cover are a favorite feeding area for ground squirrels and the soil is usually easy for the squirrels to work.

Monitoring and Control: Inspect trees of all ages in spring. Consider controlling ground squirrels if burrows are numerous and more than 10 percent of your trees die because of injured roots.
• For small-scale problems, trap or apply poison baits in ground squirrel burrows.
• For larger populations, use a burrow builder—a tractor-drawn device that digs underground runways—and bait them with poison. Drive the machine back and forth at regularly spaced intervals (about 25 feet apart) to make a series of parallel burrows that will intercept the natural ground squirrel burrow systems. Ground squirrels will explore these artificial tunnels and eat the poisoned bait within.
Thirteen-lined ground squirrel
Black dividing line
Hosts: Most Christmas tree species


White Grubs Title Banner
White Grubs
Phyllophaga spp.

Hosts: All Christmas tree species.

Importance: The larvae of June beetles, called white grubs, feed on the roots of Christmas tree seedlings, killing many seedlings, and slowing the growth of the rest. Injury usually occurs during the first two growing seasons after planting, and is most severe on abandoned farmland that has recently been converted to Christmas tree plantings.

Look For:
Dead or dying seedlings scattered throughout the stand.
Fibrous roots missing from dead seedlings. Dig or gently pull up seedlings to examine roots.
MAY TO SEPTEMBER
White C-shaped larvae, up to 1 inch long, with brownish heads and six brown legs. Dig in the upper 6 inches of soil.

Biology: White grubs normally feed on grass roots, but will eat roots of tree seedlings, especially when grass roots are scarce. In May or June, the adult beetles emerge from the soil and feed on broad-leaved hardwoods near the field. They return to the field to lay eggs in the soil. The hatched larvae burrow deeper in the soil and feed on roots for two to five growing seasons before becoming adults. Seedlings that are J-rooted because of careless planting are often killed first.

Monitoring and Control:
Before Planting: Check planting sites in July and August of the year before planting, except during long periods of drought. Run a furrow and look for grubs. If you find 1 grub per 10 linear feet, treat seedlings or site just before or during planting.
After Planting: Check monthly throughout the growing season for 3 years after planting. Treat infested blocks in the plantation if you find any grub-killed seedlings.
• Application of a fertilizer with high potassium and phosphorus and low nitrogen in fall may stimulate root production on damaged seedlings.
• Apply a registered insecticide following directions on the label.

NEXT CROP
• Apply a registered, granular insecticide before planting as described above. Use a broadcast and disk treatment for nursery beds.
• Or, dip seedling roots in a registered insecticide solution before planting.
• Spread roots out in planting hole to prevent J-rooting.
• Use herbicides to control grasses before August in the year before planting. Do not plant seedlings in areas with heavy grass cover.
White Grubs
Black dividing line
Hosts: All Christmas tree species


Wood Borers and Bark Beetles
Wood Borers and Bark Beetles Monochamus spp., etc.; Ips spp.

Hosts: All Christmas tree species.

Importance: The larvae of wood borers and bark beetles attack and destroy the woody tissues—branches, stems, and roots—of weak, dying, or dead Christmas trees. A few species of bark beetles can kill very weak trees that might have survived if left unattacked.

Look For:
Dead or dying trees or parts of trees.
Galleries (chambers) and tunnels under loose bark that have been made by bark beetles or wood borers. They may contain white larvae, 1/16 inch to 1 inch long, or adult beetles. Listen for borers gnawing on the wood.

Pests that cause similar symptoms: Pine root collar weevil, pine wood nematode, and Pales weevil carve galleries in the roots below wood borers and bark beetles. (See also pine shoot beetle.)

Biology: Adult wood borers and bark beetles lay eggs in the bark of weak and dead Christmas trees. The larvae tunnel in and feed on the bark and woody tissues, often sharing the host with several different insect species. Bark beetles may eventually emerge from one tree and attack surrounding weak trees.

Monitoring and Control: Inspect trees of all ages during and after periods of drought, grass fire, and other disturbances. Look for pockets of dead trees and treat accordingly.
• Remove and burn or chip dead or infested trees to get rid of the insects.
• Look for the primary source of the problem, i.e., what is weakening or killing trees before the borers or beetles infest them.
• Maintain vigorous trees; fertilize or irrigate as needed.
NEXT CROP
• Do not replant on stressful or marginal sites until you have identified and controlled the problem that weakened the trees.
Wood Borers and Bark Beetles
Black dividing line
Hosts: All Christmas tree species


Yellow-Bellied Sapsucker Title Banner
Yellow-Bellied Sapsucker
Sphrapicus varius L

Hosts: Scotch and Austrian pine; occasionally other conifers.

Importance: Sapsuckers peck holes in the bark of sapling Christmas trees, causing trees to bleed sap. Individual trees are often repeatedly attacked, and when severely injured, they may die. The injury also permits insects and pathogens to enter the tree.

Look For:
Evenly spaced rows of large pits or holes ¼ inch or larger on trunk of tree.
Upper portion of tree dead or dying.
Robin-size woodpecker with bands of red, black, and white on the head. The belly is yellow and the back is white and black.

Biology: The sapsucker is a forest bird that feeds on tree sap, the inner bark of trees, and the insects that get caught in the sap flowing from wounds on the trunk. This migratory bird is a fairly common summer resident, but rarely a winter resident.

Monitoring and Control: Examine trees within 3 years of harvest. If you notice any damage that might degrade or kill trees, take action to discourage the birds.
• Sapsuckers often peck on stressed trees. This can include trees planted on the wrong site (e.g., too wet, dry, or infertile), or trees affected by insect, disease, or mechanical injury. When conditions causing the stress are corrected, sapsucker attacks usually stop.
• Apply a very thin 2- or 3-inch band of a sticky substance such as Tanglefoot® just below and above the newly made row of holes to discourage the birds. Repeat if they attack new trees. Keep in mind that control is difficult and may not be justified in most cases.

NOTE: The yellow-bellied sapsucker is protected by the Federal Migratory Bird Treaty Act.
Yellow-Bellied Sapsucker
Black dividing line
Hosts: Scotch and Austrian pine; occasionally other conifers


Zimmerman Pine Moth
Zimmerman Pine Moth
Dioryctria zimmermani (Grote)
Hosts: All pines, especially Scotch and Austrian; rarely spruces and firs.

Importance: Caterpillars feed just under the bark on tree stems, large branches or sometimes on the terminal leader. Feeding may result in dead shoots or a dead leader. Pitch masses on the stem may reduce tree value. Repeated stem attacks may cause trees to break off at the injury site.

Look For:
Coagulated pitch mass on the stem, often at a branch whorl or on shoots near the terminal leader. Reddish frass may be mixed in with the pitch. The main stem may be swollen above the mass, or broken off if tree is heavily injured. On Scotch pine, the attack site may be on a gall caused by one of the gall rusts of pines.
Discolored or broken leader (sometimes a lateral), directly above a mass of coagulated, white or pinkish pitch.
LATE MAY TO AUGUST
Pinkish-green larvae, up to ¾ inch long, located in tunneled area under pitch masses. Brown pupae, ¾ inch long, can be found at the exit of feeding tunnels from mid July to late August.

Biology: Tiny caterpillars overwinter in bark crevices. They become active between early April and early May and bore under the bark and into the shoot, stem, or rust gall. They form a characteristic pitch mass at the entrance to the tunnel where they feed and later pupate. Adults emerge between mid July and late August and lay eggs on the bark. The hatched caterpillars spin and overwinter in silken cases.

Monitoring and Control: Inspect plantations regularly throughout the growing season. On Scotch and Austrian pine, look for pitch masses on the main stem. On other pines, including Austrian, look for pitch masses on shoots near the terminal leader.
• Cut out area with pitch mass on main stem using a pocket knife or shearing tool.
• Hand prune and destroy occasional injured shoots.
• Remove and destroy (by chipping or burning) infested trees by early July to prevent adult moths from attacking other trees.
• When insect is abundant or repeatedly attacks the main stem, apply a persistent registered insecticide between early April and early May as the weather warms. Emerging larvae are most vulnerable to pesticides at this time before they bore under bark. Use enough nozzle pressure and water to drench stem and branch bark.
• Do not ship infested trees because overwintering larvae hitchhike to new areas this way.

NEXT CROP
• Plant resistant varieties of Scotch pine, particularly the short-needled varieties, such as Greece, Turkey, or others from West and South Eurasia (see Table 1).
Zimmerman Pine Moth
Black dividing line
Hosts: All pines, especially Scotch and Austrian; rarely spruces and firs