Shoot Branch Injury Title Banner
 
Shoot Branch Injury Graphic  
Shoot/Branch Injury

Needles on shoots or branches uniformly discolored - usually red, yellow, or brown. Foliage may be black from sooty mold fungus. Frothy spittlemasses, aphid colonies, or scales may be on bark. If needles on shoots are cut off and webbed together, see previous section. If galls are present, see next section.


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Adana Tip Moth Title Banner
Adana Tip Moth
Rhyacionia adana Heinrich

Hosts: Scotch, Austrian, and red pine.

Importance: The caterpillars of this moth bore into the buds and developing shoots of seedlings and Christmas trees. This kills and deforms shoots, stunts growth, and degrades trees. Adana tip moth is most commonly carried into plantations on infested nursery stock.

Look For:
Dead and dying, stunted, or stubby shoots anywhere on the tree or seedling. Shoots are killed before the needles fully expand.
Small hole at the base of the dead shoot
MAY TO JUNE
Yellowish to reddish-brown blackheaded larvae, up to 3/8 inch long, on or inside the new shoot.
AUGUST TO APRIL
• Pupae in soil-covered cocoons attached to the root collar of the tree (where the mainstem and the roots meet, under the soil).

Pests that cause similar symptoms: Sphaeropsis shoot blight, European pine shoot moth, pine shoot beetle.

Biology: Adult moths emerge in April as the weather warms, and the females lay their eggs on the needles. Hatching larvae soon bore into and mine (hollow out) needles near the bud. By early June, larvae leave the needles and tunnel into developing shoots, killing the shoots before they fully elongate. This insect overwinters as a pupa in a cocoon attached to the root collar of the tree.

Monitoring and Control: Inspect trees of all ages when shoots begin to expand in April or May. Treat entire plantation if injury becomes too extensive to control with normal shearing. If trees are too small to shear, consider treating the plantation if 10 percent or more of the trees are injured.
• Shear off and destroy crooked, injured leaders and shoots to restore trees to good form.
• Spray trees or seedlings with a registered insecticide in mid to late April to kill emerging larvae. Repeat if needed in late May or early June.
• Do not ship infested nursery seedlings in fall or spring because the pupae hitchhike to new areas this way.
NEXT CROP
• Plant only pest-free nursery stock.
Adana Tiip Moth
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Hosts: Scotch, Austrian and red pine


Aphids Title Banner
Aphids
Cinara spp.; Eulachnus agilis (Kaltenbach); Cinara strobi (Fitch)

Hosts: All Christmas tree species.

Importance: Aphids suck juices from branches, shoots, and needles of Christmas trees. Affected trees may lose their needles, attract secondary pests, and become unfit for Christmas tree sale. The spotted pine aphid is one of the most common aphids on pine Christmas trees.

Look For:
Discolored sparse foliage anywhere on the tree. Scattered groups of needles turn yellow or red in summer and drop off in fall. Surrounding foliage may look sooty and glisten as if lacquered. Bees and ants may be abundant on the foliage.
MAY TO NOVEMBER
Small, winged or wingless insects clustered on the shoots or needles. Aphids may be yellow-green, brown, or black, and are usually 1/8 inch long. The spotted pine aphid, which is greenish with black spots, grows to 1/4 inch long. Some species are naked, and others are covered with a woolly wax (see Pine bark adelgid).

Biology: Most aphids overwinter on trees as eggs. Nymphs hatch in spring and quickly mature and reproduce. Several overlapping generations can produce large populations by late summer. Droughty weather at this time will increase needle fall. Applying nitrogen fertilizers when trees are young tends to increase aphid numbers.

Monitoring and Control: Begin checking trees 2 years before harvest, starting in early summer and continuing regularly until frost. Control may not be needed in the years before harvest if lady bugs and other predators are abundant. Treat individual, infested trees only if more than 30 percent of the shoots have aphid colonies. However, treat all infested trees if fields will be harvested in the current year.
• Wash off black discoloration caused by sooty mold by spraying affected tree parts with a solution of 4 ounces liquid detergent mixed in 100 gallons of water. Apply under high pressure in late afternoon, leave overnight, and then rinse trees with water the next morning.
• Limit the use of broad-spectrum insecticides that kill helpful aphid predators.
• Control mound ant colonies; these ants protect aphids by discouraging the natural enemies of aphids (see Allegheny mound ant).
• Spray trees if necessary with a registered insecticide to control large aphid populations. An insecticidal soap may be a good alternative to a conventional insecticide and will be less harmful to beneficial insects.
Aphids
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Hosts: All Christmas tree species


Broom Rust of Fir Title Banner
Broom Rust of Fir
Melampsorella caryophyllacearum J. Schrot
Host: Balsam, Fraser, and white fir.

Alternate Host: Chickweed.

Importance: This disease causes the formation of witches’ brooms within the trees, reducing quality. The incidence of infected trees is usually very low within a plantation, thus this disease is rarely considered a major threat to Christmas trees.

Look For:
JUNE
Short, thick, upright shoots that contain stunted, thickened, pale green needles.
JULY TO AUGUST
Yellow needles in the broom. Orange-yellow pustules on the underside of the needles in the broom.
SEPTEMBER
Needles in the broom falling to the ground, leaving a mass of stunted, thick shoots.

Biology: Buds are infected in the spring by wind-blown spores from chickweed and the fungus moves into the branch. One year after infection, stunted, thick shoots grow upright out of the infected branch. Spores are produced on the foliage within the broom. Shoots within the broom will produce foliage each year which will in turn produce spores in the summer. These spores infect chickweed, the alternate host. This disease is only a problem when chickweed is present in the area.

Monitoring and Control: Examine your trees in July and August. The yellow brooms will be conspicuous. Disease incidence will rarely reach a level that causes concern. If it does, consider controlling the chickweed within the plantation.
• Cut brooms off of infected trees. Once the foliage and woody broom material dries out, the fungus will die.
• If disease incidence is high, mow or kill chickweed in and around plantation.
• There are currently no fungicides labeled for broom rust.

NEXT CROP
• Inspect nursery stock before planting; do not plant infected trees.
• Examine areas around potential plantation sites. If broom rust is present in the native balsam or Fraser fir, be prepared to accept some level of disease or plant species other than balsam, Fraser, or white fir.
Witches' broom on balsam fir trees
Witches' Broom #1 Witches' Broom #2 Witches' Broom #3
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Host: Balsam, Fraser and white fir


Deer  Title Banner
Deer Odocoileus virginianus Miller

Host: All pines, Douglas-fir, Fraser fir and other true firs, Norway spruce, and white spruce.

Importance: Deer feed on the shoots of young trees. In large numbers, these animals can cause extensive damage to tree plantings. Heavily browsed trees may be too deformed to be sold as Christmas trees.

Look For:
Bark damage from deerThe ragged, squared-off ends of deer browsed twigs, ½ inch or less in diameter, on the lower 6 feet of the tree. Shredded bark and wood may hang from cut twigs.
Deer droppings and tracks near trees.
Strips of shredded or damaged bark on stems of large seedlings and saplings. Bucks may rub the bark off when polishing their antlers against stems in early fall.

Pests that cause similar symptoms: Rabbit and hare.

Monitoring and Control: Examine trees of all ages throughout the year, especially in the early spring. If 5 to 10 percent of the trees are injured, contact a conservation officer or a wildlife pest control specialist to help determine if reduction of the deer population is appropriate under local conditions. No control is needed if injury is random and infrequent.
• Use a deer repellent for short-term control (2 to 6 weeks) when appropriate.Limb damage from deer Keep in mind that some deer repellents are often ineffective
and all must be reapplied frequently, at intervals of 2 to 12 weeks.
• If damage is often severe, consider fencing fields with permanent woven wire fencing 8 feet high or 7–wire high tensile strength steel electric fence to exclude deer.
• In some states, wildlife management agencies may offer programs to assist landowners in reducing deer numbers. Contact the appropriate agency in your state for information on hunting and crop depradation programs.

Above right:
Deer may rub the bark off when polishing their antlers

Right:
Deer-browsed branches on lower half of tree
NEXT CROP
• Avoid planting vulnerable species where deer are known to congregate during the winter. Consider planting Colorado blue spruce or balsam fir in vulnerable areas.
• Consider fencing fields to exclude deer if damage is often severe.
Black dividing line
Host: All pines, Douglas-fir, Fraser fir, Norway spruce, and white spruce


Eastern Pine Shoot Borer
Eastern Pine Shoot Borer
Eucosma gloriola Heinrich

Hosts: All pines; white spruce; Douglas-fir.

Importance: The caterpillar of this small moth usually attacks new lateral (side) shoots. When abundant, larvae can damage the general shape of the crown by killing many shoots. The terminal leader of pines is sometimes attacked, affecting tree form.

Look For:
JUNE TO OCTOBER
Flagged (discolored) shoots on pine and spruce. The 6- to 8-inch long ends of shoots turn yellow and then red. Douglas-fir shoots wilt and droop before yellowing, curling into the shape of a shepherd’s crook. (Do not confuse shepherd crooking with white pine weevil injury, which looks similar, but occurs only on the terminal (topmost) shoot and down to the stem below the first whorl of branches.)
Terminal leaders or large branch ends broken over near their bases, leaving distinctive, flat stubs.
An oval hole at the base of the injury through which the caterpillar has escaped.
Caterpillars feed down the center of shoots, packing sawdust-like frass into the tunnel behind them. Identify pest by cutting shoot lengthwise with a knife. If cut before mid July, you may find a single, dirty white to gray larva, up to ¾ inch long, in the shoot.

Pests that cause similar symptoms: Sphaeropsis shoot blight, European pine shoot moth, jack pine tip beetle, pine shoot beetle, white pine weevil.

Biology: Female moths emerge in May and lay eggs on the new shoots. Young larvae bore into and feed in the center of elongating shoots. After chewing a hole at the base of the feeding tunnel, mature larvae emerge and drop to the ground to pupate and overwinter.

Feeding tunnel Monitoring and Control: Examine trees of all ages from midsummer to frost. If you find more than 10 injured shoots per tree and trees are within 2 years of harvest, treat entire plantation next spring.
• A registered insecticide can be applied to trees in mid May to kill larvae before they bore into shoots. Do not delay treatment. By the time injury is apparent, most larvae have left the shoots, and control will not be effective.
• Most injured shoots are removed when trees are sheared. Forked trees should be correctively pruned by removing excess terminals. You may want to clip off damaged shoots on trees before marketing.

NEXT CROP
• Plant resistant varieties of Scotch pine, such as Swedish, Riga, or Scandinavian.
Eastern Pine Shoot Borer
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Hosts: All pines; white spruce; Douglas-fir


European Pine Shoot Moth Title Banner
European Pine Shoot Moth
Rhyacionia buoliana (Denis & Schiffermuller)

Hosts: Scotch, red, and Austrian pine.

Importance: The caterpillars of this moth bore into the buds and developing shoots of Christmas trees. This kills or deforms shoots, stunts growth, and can make Christmas trees unfit for sale. This insect’s range is limited by very cold weather. It is rarely found in the northern half of Wisconsin, Minnesota or in the western half of upper Michigan.

Look For:
Dead, stunted, or stubby shoots anywhere on the tree. Shoots usually die before needles expand.
Hardened globs of pitch where larvae have bored into shoots.
Distorted, bushy, or multileadered trees.
MID APRIL TO EARLY JUNE
Brownish, caterpillars with black heads, up to 5/8 inch long, on or inside new shoots.

Pests that cause similar symptoms: Adana tip moth, Sphaeropsis shoot blight, Nantucket pine tip moth, pine shoot beetle.

Biology: In the spring, caterpillars bore into healthy shoots to feed and pupate. New adults emerging in June and July produce caterpillars that bore into needles and buds to overwinter. During particularly cold winters, only caterpillars that are insulated on branches below the snowline will survive. Dry weather and poor soil conditions encourage population buildup.

Monitoring and Control: Inspect trees of all ages in April and May. Randomly select 30 to 50 trees scattered throughout the plantation and look for larvae and injury. Consider treating entire plantation if 10 percent or more of the young trees are injured or if the older trees average more than 5 injured tips per tree.
• If attacks are light and scattered, prune and destroy attacked shoots before June.
• Wait to shear trees until mid July when shearing will remove most of the eggs or larvae on shoot tips.
• Prune crooked, injured leaders and branches while shearing to restore trees to good form.
• Remove the lower whorl(s) of branches from your best Christmas trees to prevent larvae from overwintering below the snowline and surviving. This will also give the trees “handles” and make harvesting easier.
• Do not ship infested nursery stock or Christmas trees because overwintering larvae hitchhike to new areas this way.
• If necessary, spray trees with a registered insecticide during the first 2 weeks of April to kill larvae as they migrate to new shoots. Trees can be treated again in late June or early July after larvae hatch from the eggs.
European Pine Shoot Moth
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Hosts: Scotch, red and Austrian pine
Frost Injury Title Banner
Frost Injury

Hosts: Balsam fir; Fraser fir; Douglas-fir, spruce; occasionally pine.

Importance: Below-freezing temperatures in early spring can kill emerging shoots and degrade Christmas trees. Susceptible trees may become stunted or bushy if injured by frost several years in a row.

Look For:
Frost Injury MAY TO JUNE
Brown, wilting and dying shoots of the current year’s growth. New shoots will develop next to the dead ones.
Live, crooked shoots.
AUGUST TO OCTOBER
Dead shoots remaining on trees until late autumn. They may not drop until spring.

Monitoring and Control: Examine trees of all ages after a late spring frost. Take recommended actions if any noticeable damage occurs.
• Remove dead shoots when shearing.
• Harvest trees growing in frost pockets—low areas where damaging frost frequently occurs—as soon as possible.
NEXT CROP
• Avoid planting highly susceptible species, such as true firs and
Brown, wilting and
dying shoots
Douglas-firs, in frost pockets. Pines may prove to be less
susceptible. However, most frost pockets are not good sites for
growing any conifer and should be avoided.
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Hosts: Balsam fir; Fraser fir; Douglas-fir, spruce; occasionally pine


Jack Pine Tip Beetle Title Banner
Jack Pine Tip Beetle
Conophthorus banksianae McPherson

Hosts: Scotch and red pine.

Importance: The larvae (grubs) of this small beetle kill terminal (top) and lateral (side) shoot tips by feeding in shoots. Dead shoot tips fall off the tree by autumn, producing a harmless effect similar to shearing. Trees may be degraded by forking if two or more lateral buds develop and become leaders. Problems occur mostly when Christmas trees are planted next to a jack pine stand.

Look For:
MAY TO OCTOBER
Jack Pine Tiip BeetleYellow or red shoot tips, mostly toward the top of the tree. The top 1 inch of the tip dies and leaves a flat stub where broken off.
A small pitch tube—glob of pitch with a hole in it—about ½ inch behind the bud.
A dark-brown beetle, about 1/16 inch long, or several smaller, white larvae inside the injured tip. Peel away the bark on the shoot tip to find the insect.

Pests that cause similar symptoms: Eastern pine shoot borer, pine shoot beetle, and Sphaeropsis shoot blight.

Monitoring and Control: Inspect trees 2 years before harvest, and treat during regular shearing.
• Shear injured tips during routine trimming. Injured tips missed in shearing will probably fall off naturally.
Pich tube below the bud
• Prune excess leaders to prevent forking.

NEXT CROP
• Avoid planting susceptible pines within 50 feet of jack pine.
Black dividing line
Hosts: Scotch and red pine


Leucostoma Canker Title Banner
Leucostoma Canker
(=Cytospora Canker)
Leucostoma kunzei (Fr.:Fr.) Munk
Hosts: Spruces, especially Colorado blue and Norway.

Importance: This fungus usually infects trees older than 15 years that are stressed by drought, winter injury, or other diseases. Branch cankers degrade trees by killing foliage and branches. Stem cankers can eventually kill trees.

Look For:
Brown needles on lower branches. Dead needles may drop off immediately or stay on the tree for up to a year. Leucostoma canker gradually kills lower branches, then spreads to higher branches.
Large, white patches of pitch at canker sites. Cankers are hard to spot if pitch is not present because the bark looks normal. Use a hand lens to find tiny black fruitbodies in the bark above the canker. Cut away bark to see the dead brown areas of the inner bark.

Factors that cause similar symptoms: Drought.

Biology: Spores ooze from the fruitbodies in threadlike masses during wet weather and are spread by rain, wind, and cultural activities, such as pruning. The fungus infects stressed trees through wounds.

Monitoring and Control: Inspect old trees, especially those 15 years or older. Look for brown needles on dead lower branches at any time of year. Treat individual trees as soon as you notice injury.
• Remove infected branches. Do not prune or shear infected trees during wet weather because spores released at this time may be carried from tree to tree on pruning tools.
• Improve tree vigor through cultural practices, such as fertilization and weed control.
• Sell trees growing on poor sites as soon as possible if Leucostoma has been a problem in your plantation. These trees are more likely to be infected than those growing on good sites.
• Avoid wounding trees because wounds are entry points for the fungus that causes Leucostoma canker.
NEXT CROP
• Do not plant susceptible species on poor sites.
Leucostoma Canker
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Hosts: Spruces, especially Colorado blue and Norway


Nantucket Pine Tip Moth Title Banner
Nantucket Pine Tip Moth
Rhyacionia frustrana (Comstock)

Hosts: Scotch, Austrian, and red pine.

Importance: The caterpillars of this moth kill and deform shoots of nursery and plantation Christmas trees. The trees may become bushy and misshapen and are therefore degraded as Christmas trees. This pest occurs mainly in the southern portions of the North Central Region.

Look For:
Dead or dying new shoots with expanded needles anywhere on seedlings or trees.
MID MAY TO AUTUMN
Brown to orange larvae, up to 3/8 inch long, on or inside new shoots.
Small, tent-like webbing on surface of needles or at base of shoots.

Pests that cause similar symptoms: Sphaeropsis shoot blight, European pine shoot moth, pine shoot beetle.

Biology: Pupae overwinter in hollowed out shoots. Adult moths emerge and lay eggs on the shoots in April when the weather warms. Newly hatched larvae feed on new, expanding shoots under small, tent-like webs, and then pupate 3 to 4 weeks later. One or more generations follow. Dry weather and poor soil conditions encourage population buildup.

Monitoring and Control: Examine trees of all ages, especially in nurseries and during the first 5 years after planting. Check trees closely in mid to late April.
• If the attack is light (less than 5 percent of trees) and scattered, prune and destroy the injured shoots.
• Shear when larvae are feeding to remove infested shoots.
• If attacks are on more than 5 percent of the trees, thoroughly spray shoot tips with a registered insecticide between mid May and mid June (timing depends on latitude) to control young larvae Dead shootsbefore they conceal themselves. You may need to treat again between mid July and late August to control additional generations of larvae.
• Do not ship infested nursery seedlings or Christmas trees because overwintering pupae hitchhike to new areas this way.

NEXT CROP
• Plant only pest-free nursery stock.

Nantucket pine tip moth







Dead shoots with expanded needles
Nantucket pine tip moth larva inside shoot
Black dividing line
Hosts: Scotch, Austrian and red pine


Northern Pine Weevil Title Banner
Northern Pine Weevil
Pissodes approximatus Hopkins
Hosts: All pines and spruces.

Importance: This insect causes minor damage in Christmas tree plantations where weak or dead pines are left standing, or where many fresh stumps are available for weevil breeding. Heavy feeding by adults may kill some shoots, leaving dead spots in the crown and slightly degrading Christmas trees. Heavy feeding may kill seedlings. Larvae may be found infesting young trees (2 to 5 years old) that are growing very slowly, generally because of heavy grass competition.

Look For:
Flagged (discolored and deformed) shoot tips anywhere on trees or seedlings.
Small, circular feeding wounds (“drill holes”) at the base of injured shoots. Pitch may ooze from the wounds.
Small, white pupae or C-shaped larvae, 1/3 inch long, beneath the bark of dead trees or stumps.
Elliptical chambers in the wood beneath the bark, each covered with a ½ inch-long chip cocoon, made of fine wood shavings.
Light-brown, white-spotted weevils, l/3 inch long, feeding on pine shoots after dark.

Pests that cause similar symptoms: Pales weevil causes more widespread damage by stripping off bark; Saratoga spittlebug.

Biology: Female weevils lay eggs in the spring on the inner bark of stumps and recently dead, dying, or severely stressed trees. Larvae mature under the bark and make chip cocoons to pupate-in. After pupating in August, weevils emerge and feed on the inner bark of twigs and small branches. They overwinter in the litter around infested trees.

Monitoring and Control: Inspect trees of all ages, especially where fresh stumps are available. In June, look for pitchy “drill holes” or flagged tips on seedlings or older trees. Treat entire nursery or plantation if seedlings show any injury or if older trees have 5 or more flagged tips per tree. Infestations lighter than this do not need control because most flagged shoots will fall off before harvest.
• Remove, chip, or burn dead or dying pines and fresh stumps before late spring to eliminate the weevils’ breeding material.
• Or, in April to mid May, drench fresh stumps and nearby soil once with a registered insecticide to kill the egg-laying adults. A similar drench in August will kill emerging adults.
• Spray living trees once with a registered insecticide in August or September to kill the feeding adults.
• When harvesting, leave one whorl of live pest-free branches on each stump to keep it alive and therefore unattractive to the weevils. Destroy these stumps within 3 years. Caution: Do not leave live branches that have needlecast diseases.
• Control grass competition around young trees.

NEXT CROP
• Delay replanting a cutover area for 2 years unless stumps are removed or treated to prevent weevil attack.
Northern Pine Weevil
Black dividing line
Hosts: All pines and spruces


Pales Weevil Title Banner
Pales Weevil
Hylobius pales (Herbst)

Hosts: Eastern white and Scotch pine; Douglas-fir; occasionally other pines, true firs, and some spruces.

Importance: This insect is a chronic problem in Christmas tree plantations where periodic harvests leave many pine stumps suitable for weevil breeding. The adults feed on the stem bark of seedlings and on the shoot and branch bark of older pines and other conifers. Seedlings die. Heavy feeding girdles and kills shoots, thereby thinning and degrading Christmas trees.

Look For:
JUNE TO AUGUST
Dead seedlings.
Dead shoot tips on large trees.
Small, irregular patches of exposed wood on seedling stems or at the bases of flagged shoots on large trees. Pitch may ooze from the wounds, or the scars may be partially callused.
White, C-shaped larvae or pupae, ½ inch long, beneath the bark of the roots of fresh pine stumps. The insects are in chambers (galleries) that run along the grain of the wood. Remove root bark with a knife to see insects.
Reddish-brown to black, robust weevils, 1/3 inch long, under the litter around live trees and stumps. Adults are on the trees during warm nights (temperature above 50ÞF) from April to September. To locate them, put a sheet under the tree after dark and shake the tree. Weevils will fall onto the sheet. Or, bait the weevils in spring by placing freshly cut pieces of pine stem on the ground near trees. Look for adults under the cut pieces during the day.

Pales Weevil damage

Pests that cause similar symptoms: Dead shoot tips can be caused by Sphaeropsis shoot blight, Saratoga spittlebug, white pine blister rust, eastern pine shoot borer, and pine shoot beetle. Pine root collar weevil, and pine root tip weevil adults are nearly identical to pales weevil and have similar life cycles. Wood borers and bark beetles carve distinctive galleries in the stump collar above the pales weevil galleries. Wood borers leave holes in the tops of old stumps.

Biology: Drawn by the odor of fresh pine resin in spring, female weevils lay eggs in the inner bark of new stumps. Larvae tunnel a few inches to several feet into the roots during the summer. Adults emerge in late summer to early fall. They spend the day in the litter around the trees and move onto trees at night to feed on the bark of shoots or seedlings. Later in the fall, they move to the litter to overwinter. Pales weevil commonly occurs along with the northern pine weevil.

Monitoring and Control: Examine trees of all ages in June, especially where fresh stumps are present. Examine 50 or more trees scattered throughout the plantation. Treat entire nursery or plantation if seedlings show any injury or if older trees average 5 or more flagged tips per tree.
• Remove new stumps by early spring to eliminate the weevils’ breeding material.
• Or, once between early April and mid May, thoroughly drench the stumps and nearby soil with a registered insecticide to kill egg-laying adults. A similar drench in August will kill emerging adults.
• Or, apply a registered insecticide to live trees between mid August and mid September when adults move onto trees to feed on shoots.
• When harvesting, leave one whorl of live, pest-free branches on the stump to keep it alive and therefore unattractive to the weevils. Destroy these stumps within 3 years. Caution: Do not leave live branches that have needlecast diseases.

NEXT CROP
• Delay replanting a cutover area for 2 years unless stumps are removed or treated to prevent weevil attack.
• Dip the above-ground portion of seedlings in a registered, residual insecticide before planting to prevent weevil feeding.
Pales weevil adult


Pine Grosbeak Title Banner
Pine Grosbeak
Pinicola emicleator lecura (Müller)

Hosts: Scotch pine; occasionally eastern white and red pine, and spruce.

Importance: Pine grosbeaks feed on the buds of Christmas trees, stunting height growth and thinning crown foliage. This feeding causes dormant buds to develop into bushy clusters of shoots that deform and degrade trees. The extent of damage varies from year to year, depending on the number of birds and the supply of other food available during the winter months.

Look For:
WINTER
The pine grosbeak—a robin-sized bird with a large, cone-shaped beak. Adult males are gray with a rosy-red coloring in the crown, rump, and breast. In females, these areas are suffused with yellow.
Buds missing from the topmost shoot and the upper branches of trees.
Broken leaders on trees taller than 5 feet.
MAY TO JULY
Bushy foliage in the upper part of the tree, sprouting from lateral (side) buds that normally remain dormant.

Biology: During the winter months when their normal food supply is depleted, grosbeaks may migrate from the northern forests south to areas that provide adequate food and shelter, such as Christmas tree plantations. Normally this only happens once every 4 or 5 years.

Monitoring and Control: Inspect trees within 2 or 3 years of harvest and protect them if you notice flocks of grosbeaks daily during the winter.
• If practical, install an electric noise broadcasting system to repel birds. Alter the kinds of sounds broadcasted every 3 to 5 days.
• Place a plastic mesh sleeve over the topmost shoot after the tree has become dormant, and remove it the following spring. This control is most practical for protecting high-value trees ready for harvest.
• Shear damaged trees to help restore good form.

Note: The pine grosbeak is protected by the Federal Migratory Bird Treaty Act.

NEXT CROP
• Plant resistant varieties of Scotch pine, such as S. French, Poland, Belgian, or Czechoslovakia (see Table 1 for resistance rankings of Scotch pines).
Pine Grosbeak adults
Black dividing line
Hosts: Scotch pine; occasionally eastern white and red pine, and spruce
Pine Root Tip Weevil Title Banner
Pine Root Tip Weevil
Hylobius rhizophagus Millers, Benjamin, & Wagner

Hosts: Scotch and red pine; eastern white pine if mixed with Scotch pine.

Importance: Larvae (grubs) of this weevil feed on the root tips of Christmas trees, preferring trees grown from stumps (tip-ups) because of the large root systems on these second-crop trees. Injured Scotch or red pines become discolored and may die. White pine may be attacked if grown near susceptible pines, but few will be killed. This weevil is found mostly in the northern Lake States.

Look For:
Flagged (deformed and discolored) shoots and branches anywhere on the tree. Some trees may be dead.
• Debarked, hollowed-out root ends where root tips have been chewed off.
• White, C-shaped larvae, up to ½ inch long, which may be in the root.

Pests that cause similar symptoms: Sphaeropsis shoot blight, pine spittlebug, Saratoga spittlebug and Scleroderris canker. Pales weevil adults and pine root collar weevil adults are nearly identical to pine root tip weevil adults in appearance.

Biology: Larvae and adults overwinter underground. Adults emerge in April and lay eggs in June. Newly hatched larvae feed on the rootlets and then tunnel into the main lateral (side) roots as they grow. After overwintering, the larvae continue to root feed until July, when they pupate. New adults emerge in late summer.

Monitoring and Control: If you suspect pine root tip weevil, ask a pest specialist for help in diagnosis. Treat if recommended.
• Spray trees with an insecticide registered for weevils in late July or early August to kill adult weevils as they move onto trees to feed. This treatment has not been tried for pine root tip weevil, but does control similar weevils.

NEXT CROP
• Remove any abandoned Scotch pine trees that are adjacent to areas planned for planting.
• Avoid growing trees from stumps (tip-ups).
• If the problem is serious, consider planting a nonhost species after harvest.
Pine Root Tip Weevil
Black dividing line
Hosts: Scotch and red pine; eastern white pine, if mixed with Scotch pine


Pine Shoot Beetle Title Banner
Pine Shoot Beetle
Tomicus piniperda L.

Hosts: All pines.

Importance: Pine shoot beetle is an exotic pest that can develop and feed in shoots of most pine species grown in North America. Shoot feeding by adult beetles kills shoots and could reduce growth if populations were high. However, pine shoot beetle is most important because it is a quarantine pest. Federal and state quarantines regulate shipments of pine Christmas trees from counties known to be infested with pine shoot beetle. The goal of these regulations is to reduce the risk that pine shoot beetle will be transported to new areas.

Look For:
Reddish boring dust on the bark of stumps or cut trees in spring when parent beetles are colonizing brood material.
Egg and larval galleries under the bark of recently cut pine stumps and cut trees that have been colonized by parent beetles. Egg galleries run parallel with the grain of the wood and have a slight bend at the end. Larvae feed in tunnels that are roughly perpendicular to the egg gallery.
JUNE TO DECEMBER
Attacked shoots on live pine trees with a round hole, often surrounded by a small glob of pitch. Beetles feed in tunnels down the center pith of the shoots. Tunnels are hollow and are not filled with frass. Two to five tunnels may be found on a single shoot. Attacked shoots eventually die, break off, and drop.

Pests that cause similar symptoms: Other bark beetles infest pine logs, cut trees, and stumps. Specialists can help you distinguish their galleries from pine shoot beetle galleries.

Damage caused by shoot-feeding beetles is similar to injury caused by Sphaeropsis shoot blight, eastern pine shoot borer, European pine shoot moth, and jack pine tip beetle. Shoots killed by Sphaeropsis will not have tunnels. Shoots attacked by eastern pine shoot borer and European pine shoot moth will have fine, sawdust-like frass packed into the tunnel. Jack pine tip beetle constructs hollow tunnels in shoots like pine shoot beetle; contact a specialist to tell the two insects apart.
Pine Shoot Beetle
Biology: Adult beetles overwinter in a niche in the bark at the base of live pine trees. In early spring, adult beetles fly to recently cut or dying pine trees, logs, or stumps. This spring flight may occur between mid February and mid April in North Central states. Adults bore into the inner bark, mate, and females construct egg galleries. Eggs are laid along the sides of the gallery and hatch within a few weeks. Larvae feed in the inner bark for 6 to 10 weeks and pupate. New adults emerge in early summer, often in early to late June. These reddish-brown adults feed in current-year or one-year-old shoots on live pine trees until October or November. During this maturation feeding, adult beetles darken to a shiny black color. After a few hard frosts, beetles move to the base of trees to overwinter.

Monitoring and Control: If you plan to ship trees outside of your county, contact your state regulatory agency for current information on the pine shoot beetle quarantine and regulations. If you are in a regulated county, you may wish to enroll your fields in the Pine Shoot Beetle Compliance Program, a voluntary integrated management program. You may also request a preharvest inspection of fields to certify that trees are not infested with pine shoot beetle. Any evidence of pine shoot beetle infestation may cause your field to be restricted.
• Check live trees throughout the summer and fall for evidence of shoot-feeding beetles. Clip off discolored or dead shoots and split them lengthwise to find a black or reddish-brown beetle feeding in a hollow tunnel.
• The key to controlling pine shoot beetle is to reduce availability of pine stumps, cut or dying trees, and similar material needed by breeding beetles. Chip or burn culled or unsold trees in spring beforeLarvae feed in galleries the new generation of beetles can complete development.
• Cut stumps as low to the ground as possible during harvest in autumn or the following spring. Stumps can also be sprayed with an approved insecticide in late spring before new adult beetles emerge.
• Freshly cut pine trees or logs can be set along edges of fields in early spring to attract parent beetles. These trap logs must be collected and destroyed by chipping or burning before the progeny beetles emerge.
• Spraying foliage with an approved, registered insecticide can help control pine shoot beetle, but is rarely 100 percent effective. Time your spray to coincide with emergence of the new generation of beetles.

NEXT CROP
• Continue to chip or burn culled trees, cut stumps low, and practice good sanitation in fields to prevent populations of pine shoot beetle from building to damaging levels.
Cut trees should be burned
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Pine Spittlebug Title Banner
Pine Spittlebug
Aphrophora parallela (Say)

Hosts: Scotch, Austrian, and eastern white pine; all spruces and firs.

Importance: Spittlebug nymphs and adults suck sap from shoots of Christmas trees. Unless abundant, they seldom do more than flag (discolor and deform) an occasional branch tip. However, the Sphaeropsis fungus may invade weakened pines through spittlebug feeding wounds and shoot blight may heavily flag or kill trees.

Look For:
Flagged shoot tips anywhere on the tree (especially on pines). Foliage may look sooty and glisten as if lacquered. Some trees may be dead.
One or more creamy yellow to black nymphs, up to ¼ inch long in spittlemasses.
MAY TO EARLY JULY
Frothy white spittlemasses on shoots or trunk.
Symptoms of Sphaeropsis shoot blight on pines.
MID JUNE TO MID SEPTEMBER
Oval-shaped adults, about 1/3 inch long, on needles or branches. They jump when approached or touched.

Pests that cause similar symptoms: Flagged shoots could be caused by jack pine tip beetle, Pales weevil, pine shoot beetle, pine root tip weevil, Saratoga spittlebug, Scleroderris canker, or Sphaeropsis shoot blight. Sooty, lacquered foliage could be due to aphids or pine tortoise scale.

Biology: Nymphs hatch in May from eggs laid under the bark of shoots. For the next 6 to 7 weeks, they feed on the tree’s sap and produce the characteristic, frothy spittlemasses from partially digested sap. Black sooty mold grows on the sugary sap splashed from the spittlemasses. Adults appearing in July also suck the tree’s sap, but form no spittlemasses. The Sphaeropsis shoot blight fungus enters the feeding wounds and causes shoot tips to turn brown.

Monitoring and Control: Examine trees of all ages, especially those under stress, from May through June. A few scattered spittlemasses need no treatment if trees are otherwise healthy. If insects seem abundant—as if trees are partially coated with “snow”—look for flagging in late summer and early fall. If trees are flagged, or if Sphaeropsis shoot blight is also present, treat entire plantation next summer.
• Apply a registered insecticide in early to mid July to control the adults. To determine spray date, start examining spittlemasses in early July, and spray when 95 percent of them are empty. Manage Sphaeropsis shoot blight if needed.
• Wash off the black discoloration caused by sooty mold by spraying the affected tree parts with a solution of 4 ounces liquid detergent mixed in 100 gallons of water. Apply under high pressure, preferably in late afternoon. Leave overnight and rinse tree with water the next morning.

NEXT CROP
• Select appropriate species for site conditions. Trees stressed by drought, poor growing conditions, or other factors are more susceptible to spittlebug and shoot blight injury.
Pine Spittlebug
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Hosts: Scotch, Austrian, and eastern white pine; all spruces and firs


Pine Tortoise Scale Title Banner
Pine Tortoise Scale
Toumeyella parvicornis (Cockerell)

Hosts: Scotch, Austrian, and red pine.

Importance: This scale extracts sap from the woody shoots and branches of Christmas trees, and may stunt growth. High populations cause needles and shoots to become discolored, leaving trees unfit for sale. Heavy attacks may kill branches or even trees. Infested trees often become coated with black sooty mold.

Look For:
Discolored needles and dying shoots or branches, particularly on the lower branches. Needles may look black and sooty and glisten as if lacquered. Many bees and/or ants may be on the needles, and some trees may be dead.
Reddish-brown, mottled, helmet-shaped scales, up to ¼ inch in diameter, on the bark of injured shoots.

Pests that cause similar symptoms: Sooty mold can also occur on trees infested with aphids or pine spittlebug. Scattered dead branches can be caused by Sphaeropsis shoot blight, Saratoga spittlebug, or pine spittlebug.

Biology: Young females overwinter on the bark of shoots and branches and produce hundreds of eggs in the spring. In June or July, tiny crawlers (nymphs) hatch and crawl out from under the scales. Adult and larval ladybugs frequently feed on the crawlers at this time, and can usually control light infestations before trees are injured. The female crawlers attach themselves permanently to the tree and develop into soft scales. While feeding they secrete a shiny, sugary waste product called honeydew, which coats the nearby branches. Black sooty mold grows on the sugary honeydew, turning needles and shoots black. Bees and ants feed on the honeydew.

Monitoring and Control: Examine trees of all ages from May to June, looking for sooty needles. Treat individual infested trees and seedlings if scales are obvious or if trees are ready for harvest.
• Cut and burn heavily infested trees before mid June to reduce spread of crawlers.
• Coat trees completely with dormant or superior oil before buds break in spring to kill immature scales.
• Or, spray each infested tree once with a registered insecticide between mid June and mid July to kill emerging crawlers. Use a hand lens to check for pinkish eggs or small, crawling insects on the undersides of scales in mid June. The best time to spray is when almost half of these crawlers have emerged. If timing is incorrect, a second treatment may be needed.
• Control mound ants because they may protect scales from predators.
• Wash off the black discoloration caused by sooty mold by spraying affected tree parts with a solution of 4 ounces liquid detergent mixed in 100 gallons of water. Apply under high pressure, preferably in late afternoon. Leave overnight and rinse with water the next morning.
• Do not ship infested trees because scales hitchhike to new areas this way.

NEXT CROP
• Plant only pest-free stock.
• Do not plant susceptible pines next to a scale-infested stand or windbreak without first treating to control scales. Jack pine is a common host, so avoid jack pine windbreaks.
Pine Tortoise Scale
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Hosts: Scotch, Austrian, and red pine


Porcupine Title Banner
Porcupine damagePorcupine
Erithizon dorsatun L.

Hosts: All Christmas tree species.

Importance: Porcupines eat the inner bark of limbs and trunks, girdling them, and may clip off tree limbs.

Look For:
Limbs or trunk that is debarked and girdled.
Smooth, clean, slanted cuts on high branches snipped by porcupines.

Pests that cause similar symptoms: Voles, hares, and rabbits.

Monitoring and Control:
Examine trees of all ages for evidence of porcupine feeding, especially in winter.
Porcupines can be trapped with wire box traps baited with salted corn cobs.
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Hosts: All Christmas tree species


Saratoga Spittlebug Title Banner
Saratoga Spittlebug
Aphrophora saratogensis (Fitch)

Hosts: Scotch and red pine; occasionally eastern white pine, Fraser fir and balsam fir.

Alternate Hosts: Sweetfern; brambles (raspberry and blackberry); broad-leaved weeds.

Importance: Spittlebug adults feed on shoots of conifers and can discolor foliage, stunt or kill branches, and leave trees unfit for Christmas tree sale. Heavy feeding for 2 or 3 years can kill Scotch and red pine Christmas trees.

Look For:
Reddish or reddish-brown (flagged) branches, particularly in the upper part of the tree. Severely injured trees brown up and die.
Tan or brownish flecks on the wood under the bark of older portions of branches. Peel bark away with a knife to see the flecks.
Dense ground cover with sweetfern or other alternate hosts.
MID MAY TO EARLY JULY
Frothy masses of spittle-like bubbles at the base of sweetfern, brambles or other alternate hosts.
Small, red and black or chestnut-brown insects in these spittlemasses.
LATE JUNE TO SEPTEMBER
Tan and white boat-shaped insects, 1/3 inch long, on the tree. Each has a white arrow-shaped marking on its front end. Spittlebug adults will jump away when disturbed.
Saratoga Spittlebug spittlemass

Pests that cause similar symptoms: Sphaeropsis shoot blight, meadow spittlebug (green insects in spittlemasses in the tops of weeds and grasses, not a Christmas tree pest), northern pine weevil, Pales weevil, jack pine tip beetle, pine shoot beetle, pine root tip weevil, pine spittlebug, or Scleroderris canker on pine.

Biology: Nymphs hatch in spring and drop from trees to feed on alternate host plants. They cover themselves with the characteristic spittlemass made of fluids from the host plants. In late June or early July, adults return to the trees to suck sap from the shoots and lay eggs. This feeding scars the inner bark and wood and blocks vessels that carry water and nutrients to the rest of the tree.

Monitoring and Control: Examine sites before planting and check between rows of young trees after planting. Look for and eliminate pockets of sweetfern, blackberry, and raspberry if they occupy more than 20 percent of the open ground cover. Randomly select five Christmas trees scattered throughout the plantation. Scrape the bark off the 2-year-old shoot portion of any branch in the upper half of each tree, and look for flecks (feeding scars) on the wood. Consider treating adult spittlebugs if there are more than 20 flecks per 4 inches of branch length.
• Use a herbicide to limit sweetfern and brambles to less than 20 percent of the ground cover within 20 feet of the trees. Spittlebugs cannot complete their life cycle without these alternate hosts.
• Apply a registered insecticide to the trees in early to mid July to kill emerging adults before they lay eggs. The best time to treat trees is when 90 percent of the spittlemasses on sweetfern or brambles are empty.
NEXT CROP
• Use a herbicide to destroy the alternate hosts before planting trees. Limit alternate hosts throughout the growing cycle to less than 20 percent of the ground cover.
• Avoid very dry sandy soils that are prone to drought stress. These areas often have sweetfern growing on them.
Saratoga Spittlebug damage
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Hosts: Scotch and red pine; occasionally eastern white pine, Fraser fir and balsam fir


Scleroderris Canker Title Banner
Scleroderris Canker (=Gremmeniella Canker)
Gremmeniella abietina (Lagerb.) M. Morelet

Hosts: All pines; occasionally spruces, firs, and Douglas-fir.

Importance: The European strain of this disease kills trees of all ages, causing extensive losses in plantations. The North American strain only kills trees less than 6 feet tall and can seriously damage Christmas trees during the first 5 years after planting. Only the North American strain is present in the upper Midwest.

Look For:
Cankers: oblong, sunken areas on the stem and branches, commonly inconspicuous. Remove the bark and look for a slight swelling on the wood surface.
Green discoloration beneath the bark of dead branches.
MAY TO JUNE
Orange discoloration at the bases of needles, usually on the lower 3 feet of the tree. These needles fall off easily.
Dead buds on shoots that have discolored needles.
JULY TO NOVEMBER
Brown needles and branch tips. Needles fall off when touched.
DECEMBER TO APRIL
Dead branch tips with no needles.

Pests that cause similar symptoms: Sphaeropsis shoot blight and canker, drought, pine root tip weevil, pine spittlebug, Saratoga spittlebug on pine.

Biology: Branch tips usually become infected in May and June, but infection sometimes takes place from February through November. Spores are windblown or rain-splashed from infected nursery stock and infected cut Christmas trees.

Monitoring and Control: Examine trees of all ages in May or June when orange needle discoloration is most obvious. Check the lower branches of trees in low spots in the plantation, and remove infected branches immediately. Continue to check branches each year, especially if this canker is present in natural stands within ¼ mile of your plantation.
• Remove all infected branches.
• Do not shear infected foliage during wet weather because spores released at this time can be carried from tree to tree on shearing tools. Sterilize tools after shearing infected trees by dipping in denatured alcohol for 3 minutes.
• Shear healthy trees first so spores will not be carried from infected trees to healthy ones. Note: chemical controls are available to protect nursery stock, but may be too expensive for plantation use.

NEXT CROP
• Plant only pest-free nursery stock.
• Plant resistant species, such as spruce or fir, in areas where Scleroderris canker is present.
• Avoid planting in frost pockets.
Scleroderris Canker
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Hosts: All pines; occasionally spruces, firs, and Douglas-fir


Sphaeropsis Shoot Blight & Canker Title Banner
Sphaeropsis Shoot Blight and Canker (= Diplodia)
Sphaeropsis sapinea (Fr.:Fr.) Dyko and B. Sutton

Hosts: Red, Scotch, and Austrian pine.

Importance: This fungus kills current–year shoots on trees of all ages, and usually kills nursery seedlings within the first year. Repeated infection over several years eventually kills older trees. Girdling cankers are formed when Sphaeropsis infects wounds on the stem and branches.

Look For:
Stunted or curled current-year shoots. Infected tissue will be resin soaked.
Black fruitbodies on dead needles or shoot tissue.
Cankers: oblong sunken areas on branches or stem. The top of the tree above girdling cankers will be killed.
Olive-green streaking on the resin–soaked tissue beneath the bark.

Pests that cause similar symptoms: Adana tip moth, drought, European pine shoot moth, Nantucket pine tip moth, pales weevil, pine root tip weevil, pine shoot beetle, Scleroderris canker, spittlebugs.

Biology: Sphaeropsis overwinters in pine shoots, bark, cones, or litter and infects growing shoots in the spring. Spores are released during wet weather from spring through fall. Trees that are stressed because of poor sites, drought, snow damage, or insect activity are very susceptible to this disease. Wounds, such as those made by hail, shearing, or insects, serve as entry points for Sphaeropsis. For instance, this fungus frequently infects trees that have been wounded by pine spittlebug feeding.

Monitoring and Control: Inspect trees of all ages in late spring or early summer. Randomly select 50 or more trees scattered throughout the plantation and look for stunted or curled current-year shoots. If more than 10 percent of these trees are unsalable because of Sphaeropsis, consider treating the entire plantation next spring. Take other preventive measures immediately to avoid spreading the fungus.
• Control insects that are weakening trees and creating entry points for Sphaeropsis.
• Do not shear infected trees during wet weather because spores released at this time may be carried from tree to tree on shearing tools.
• Apply a registered, preventive fungicide four times, once every 2 weeks during shoot elongation, to prevent shoot blight from spreading to healthy trees.

NEXT CROP
• Plant disease-free stock.
• Avoid planting susceptible species, such as Austrian or red pine, on poor sites where they will be more vulnerable to both insect and fungal attack.
• Do not plant trees next to windbreaks that are affected by Sphaeropsis. Examine windbreaks closely; although shoots may not be infected, cones may still harbor Sphaeropsis.
• Take preventive measures as described above to protect new foliage.
Sphaeropsis Shoot Blight & Canker
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Hosts: Red, Scotch, and Austrian pine


Spruce Bed Scale Title Banner
Spruce Bud Scale
Physokermes piceae (Schrank)

Hosts: All spruces.

Importance: This scale sucks fluids from the shoots and branches of Christmas trees, but usually does not damage trees. Heavy attacks, however, may kill a few trees or stunt new shoots, leaving trees unfit for sale.

Look For:
Discolored needles and dying shoots, particularly on the lower branches.
Dusty red-brown globe-like scales, up to 3/16 inch in diameter, that look like abnormal buds at the bases of current shoots.

Biology: Young females overwinter on the bark of shoots and branches and produce hundreds of eggs in the spring. In June or July, tiny crawlers (nymphs) hatch and crawl out from under the scales. Ladybugs frequently feed on the crawlers at this time. The female crawlers attach themselves permanently to the tree and develop into soft scales.

Monitoring and Control: Examine trees the year before harvest. Ladybugs will usually control light infestations. However, if predators are not effective or if you notice scales on trees that are ready for harvest, consider control options.
• Cut and burn heavily infested trees before mid June to reduce spread of crawlers.
• Coat trees completely with dormant oil before buds break in spring to kill immature scales.
• Or, spray infested trees onceSpruce Bud Scale with a registered insecticide between mid June and mid July to kill emerging crawlers. Use a hand lens to check for pinkish eggs or small crawling insects on the undersides of scales in mid June. The best time to spray is when almost half of these crawlers have emerged. If timing is incorrect, a second spray may be needed.
• Do not ship infested trees because overwintering scales hitchhike to new areas this way.

NEXT CROP
• Plant only pest-free nursery stock.
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Hosts: All spruces


White Pine Blister Rust
White Pine Blister Rust
Cronartium ribicola J.C. Fisch.

Host: White pine.

Alternate Hosts: Gooseberry, currant, Ribes spp.

Importance: White pine blister rust causes cankers that kill branches and lower the market value of Christmas trees. Cankers on the trunk can girdle and kill trees.

Look For (on pine):
Patches of brown bark with yellow borders. This signals the first year of infection.
Spindle-shaped swellings that appear on the branches or trunk during the second year of infection.
Signs of resin flow and rodent feeding on mature yellow-bordered cankers.
Reddish-brown needles on dead branches and tree tops above trunk cankers.
MAY
Cream-colored blisters pushing through the diseased bark. These break open and release orange-yellow spores.
JUNE TO JULY
Yellow-brown blisters on the canker that produce a sticky orange fluid that later hardens and turns black.

Look For (on gooseberry and currant):
JUNE TO AUGUST
Orange spores on the undersides of leaves.
AUGUST TO OCTOBER
Brown hair-line fungal growths on the undersides of leaves.

Pests that cause similar symptoms: Pales weevil, pine root collar weevil.

Biology: This fungus needs both pine and an alternate host to complete its life cycle. It spreads from pine to gooseberry or currant, but cannot spread from pine to pine. The disease is usually most severe in regions where weather is cool and moist in August and September. Thus, the farther north, the greater the hazard of blister rust.

Monitoring and Control: Inspect 5- to 10-year-old trees in May. Randomly select 50 or more trees scattered throughout the plantation, and look for branch flagging and orange blisters on branches or trunks in May. If more than 10 percent of these trees are infected, remove cankers and control alternate hosts before August.
• When shearing Christmas trees, prune off all brown branches that have cankers. This prevents the fungus from entering the trunk and killing the tree.
• Destroy and remove trees with trunk cankers.
• Remove or kill alternate hosts with a registered herbicide.

NEXT CROP
• For best results, plant white pine in low-hazard southern zones where trees are less likely to be killed by white pine blister rust.
• Avoid planting white pine where alternate hosts are abundant, especially in high-hazard northern areas. If you do plant in these areas remove alternate hosts to reduce the likelihood of infection.
• Avoid planting white pine in areas where cool air congregates, such as at the base of a slope or in a depression.
White Pine Blister Rust
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White Pine Weevil Title Banner
White Pine Weevil
Pissodes strobi (Peck)

Hosts: Eastern white and Scotch pines, spruces; other pines are also susceptible.

Importance: The larvae of this common pest deform and degrade Christmas trees by killing the terminal leader and the top 2 to 4 years of growth. Damage will delay harvest for 1 to 3 years until those trees recover enough to be suitable for sale.

Look For:
Dead or dying terminal leader (topmost shoot on the mainstem), curled into the shape of a shepherd’s crook. Lateral (side) branches on the upper whorls may also die.
MARCH TO APRIL
Small round holes or pitch flow on terminal leader where adult weevil is feeding or laying eggs.
JUNE TO AUGUST
Slightly curved white larvae, up to ¼ inch long, under the bark or in the wood of the damaged terminal.
Clumps of fine white slivers of wood under the bark in late summer. These woody chip cocoons may contain white pupae or brownish weevils, ¼ inch long.

Pests that cause similar symptoms: Frost injury on tree tops, white pine blister rust, eastern pine shoot borer.

Biology: On warm spring days overwintering adults move from the litter to the tree tops to mate and lay eggs in feeding wounds on the bark of the terminal leader. The larvae soon hatch and bore downward under the bark, eventually girdling the top of the stem and the upper one to three whorls of branches. Larvae pupate in woody chip cocoons and emerge as adults from late July to late August. Adults feed on the bark of small branches before dropping to the litter to overwinter.

Monitoring and Control: Begin checking for dying and dead terminals in late June and concentrate on trees that will be harvested in 3 or 4 years. Treat entire plantation when injury becomes too severe to correct with pruning.
• Prune and burn infested leaders before mid July to kill the insects. Cut back all but one live lateral (side) shoot by at least half their length to maintain single-stem dominance.
• Spray the terminal leader of trees with a registered insecticide as soon as weather warms to control egg-laying weevils. Eggs are usually laid in early May in the Lake States and April in the Central White Pine WeevilStates. A second spray between mid August and late September may be needed to control newly emerged adults. The second spray should be applied to the upper half of the tree canopy.

NEXT CROP
• Avoid planting highly susceptible white pine and Norway and Colorado blue spruce. If you do plant these species, isolate them from less susceptible pines and spruces.
• Plant resistant varieties of Scotch pines, such as the Swedish variety, if available.
• If practical, remove old stands of eastern white pine or jack pine in and around plantations before planting.
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Hosts: Eastern white and Scotch pines, spruces; other pines are also susceptible