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Conifer pests
Many pest problems can be prevented by keeping trees healthy and vigorous. Tree
pests are usually attracted to and do more damage to stressed, weakened trees.
In forests, environmental stresses can sometimes be alleviated by thinning
stands to reduce competition among trees. In urban landscapes, trees are often
planted in areas where they would not grow naturally and thus may suffer from
too much or too little moisture, soil compaction, alkalinity, air pollution, and
exposure to sun and wind. In urban areas throughout New Mexico, conifers need
supplemental water during the windy spring and at other dry times during the
year.
Transplanting wild grown conifers to urban areas poses other
problems. Conifers growing in New Mexico’s dry soils have extensive root
systems. Generally, few of the roots remain intact when the trees are dug so
many transplanted trees die. The larger the tree chosen to transplant, the less
likely it will survive. Younger trees are more vigorous, have smaller root
systems, are easier to dig, and will quickly grow to a size equal to that of
larger, more costly transplants. You can double the survival rate by pruning
roots 12 months or more before digging. Cut them with a narrow pointed shovel
from 1 to 3 feet out from the tree to a depth of 12 to 18 inches. Prune roots in
November, December, or January while the tree is dormant. Conifers must be moved
with a ball of soil held firmly intact around the roots. Use tightly wrapped
burlap to keep the soil from crumbling during transportation and handling. It is
important to remove burlap, chicken wire, or any other material used to wrap the
root ball when resetting the plant in the ground. These materials don’t rust or
rot away in dry Southwestern soils and the trees will remain root bound. Please
note that white pine wildlings from Southern New Mexico should not be
transplanted elsewhere to prevent the spread of white pine blister rust.
State law prohibits removing any
plant within 300 feet of a public thoroughfare. The law also requires that
before removing any plants, you first obtain a written permit from the landowner
or land manager. If you plan to dig or sell plants, first apply for a Collected
Plant Inspection Certificate and/or a Dealers License from the New Mexico
Department of Agriculture.
Pinyon Needle Scale
Matsucoccus acalyptus
(Herbert)
Pinyon needle scales are small, black, bean-shaped bumps on the surface of one-year-old pinyon needles. These tiny, sap-sucking insects kill the needles and seriously weaken pinyon pines in forests and used as ornamentals. Reduced new growth and stunted needles are common on trees suffering repeated attacks. Heavy infestations frequently kill small trees and predispose weakened larger trees to attack by other insects, especially bark beetles, which can kill trees.
Scales infesting one-year-old needles.
BIOLOGY: Adult, wingless females emerge from scale coverings in late winter or early spring and mate with winged males. Emergence time in Southern New Mexico communities is mid to late February; in Albuquerque it is early to mid March; and in Santa Fe and Los Alamos it is mid-March to early April. Most males emerged the previous fall and spent the winter as pre pupae in silk webs in litter beneath the tree. A few males don’t enter the pre pupal stage until early spring. Mated females lay yellow eggs in clusters held together by white, cottony webbing around the root collar, on undersides of large branches, in branch crotches, or in cracks of rough bark. Occasionally, egg masses are found several feet from the base of the tree on a rock or log. About four weeks after eggs are laid, tiny, red eye spots can be seen in the eggs with the aid of a hand lens. Nymphs, called crawlers, emerge about 7 to 10 days after eye spots appear. They climb to the ends of branches and settle on the previous year’s new growth. After inserting tube like mouth parts into the needle, they become immobile, cover the body with wax, and turn black.
Heavily infested pinyon. Only the new growth remains green.
CONTROL: Potential damage from these pests can be drastically, reduced by destroying eggs before they hatch. Dislodge egg masses from the tree with a strong stream of water from a garden hose. After washing down the tree, rake up all the material around the base of the tree and destroy or remove it. Chemical insecticides are registered to control the pinyon needle scale, but timing of the spray application is critical for success. Apply insecticides to the bark and branch crotches as soon as crawlers begin to emerge. Examine eggs with a hand lens and be ready to spray shortly after the crawler’s red eve spots are visible. Once scales hi\ C established themselves on the needles, they become more difficult to control. Additional direct control information.
female scales migrating to egg-laying Sites in the cracks of rough bark.
Female scale emerging from scale covering and being mated by winged male.
Cottony webbing and eggs laid at the base of the tree trunk.
Pine Needle Scale
Chionaspis pinifoliae (Fitch)
Pine needle scale is a common pest of most pine species, spruce, and Douglas-fir. Damage is especially noticeable on ornamental pine and spruce trees growing along dusty roads. Insects feed by sucking sap from needles, causing the needles to yellow and eventually drop. Heavy infestations over several years can kill young trees and severely weaken larger trees, predisposing them to attack by other pests.
BIOLOGY: The pine needle scale has two generations per year. The eighth-inch-long mature female scales are most conspicuous. They are almost pure white, slender at the front end, and wider at the rear end. Males are smaller, more slender, and rarely seen. Twenty to 30 eggs are laid in the fall and winter beneath the dead female scale. Eggs hatch in May and the nymphs or “crawlers” move to the new green needles to feed. Nymphs mature by early July, adults mate, and new clusters of eggs are laid. Scales of this second generation mature by fall and lay the over wintering eggs.
Pine needle scale on ponderosa pine needles.
Enlarged view of female scale on a single needle.
CONTROL: Inspect trees for scales before digging or purchasing for transplant. On established trees, apply a foliar systemic insecticide in May and early June to provide some control of heavy infestations. Insecticides should be applied just before eggs hatch and then once or twice more at 7-10 day intervals to control nymphs hatching later. Adult insects are protected by a waxy covering and almost impossible to kill with contact insecticides. Summer or horticultural oils may improve effectiveness but they can discolor or burn plants if not applied correctly. Cutting or burning small infested trees is the only effective cultural control alternative to chemical insecticides. Ladybird beetles and a few species of parasitic wasps usually keep populations of this pest below seriously damaging levels.
Pinyon Spindle Gall Midge
Pinyonia edu!ico!a Gagne’
Pinyon spindle gall midge produces a spindle-shaped swelling from the needle base that is about a half-inch long. The insect is a common forest pest that rarely causes serious damage. However, in urban settings heavy infestations can cause serious defoliation as galls dry and needles drop prematurely.
CONTROL: Controlling this pest usually isn’t necessary. Landscape trees under stress that develop heavy infestations, may require treatment with a registered systemic insecticide. Apply the insecticide when eggs are laid and hatching starts in late June and early July.
BIOLOGY: The pinyon spindle gall midge is a tiny fly about 1/16-inch (3-4 mm) long. Adults lay eggs on needles in late June and early July. Larvae hatch soon afterward and mine into the current year’s needles, causing galls to form. Each gall contains from 5 to 40 small, orange, legless maggots. Larvae over winter in the galls and pupate in the spring.
Needle gall.
Tiny, orange maggots inside gall
Needle Miners
Pinyon Needle Miner
Coleotechnites edulicola Hodges and Stevens
Ponderosa Pine Needle Miner
Coleotechnites ponderosae Hodges and Stevens
Needle miners are locally common on pinyon and ponderosa pine. Species resemble one another in appearance and damage but have different life cycles. Damage first becomes evident as foliage browns. Closer examination reveals hollowed-out needles. Early needle drop, reduced growth, and tree mortality can all result from needle miner infestations. The severity of the infestation varies significantly from tree to tree, suggesting that individual trees have some resistance to these pests.
BIOLOGY: Pinyon needle miners lay eggs from early June through mid-July. Larvae emerge soon after eggs are laid and bore into uninfested needles where they feed until fall. They over winter inside the needles as dormant larvae. Feeding resumes in the spring and larvae grow to about 3/8-inch (5 mm) long. Pupation occurs in late May. Ponderosa pine needle miners lay eggs in late summer inside previously mined needles. The newly hatched larva bores into the tip of a green needle and mines slowly through the winter, developing more rapidly as the weather warms and then pupating in mid-summer.
Ponderosa pine needle miner inside needle.
Pinyon needle miner exit hole.
CONTROL: Trees usually recover from needle miner damage without suffering serious injury. For direct control, use a foliar systemic insecticide after eggs have hatched.
Pinyon needle miner damage.
Tiger Moth
Halisidota spp.
Tiger moths are most often encountered on ponderosa and piñon pines and occasionally on juniper and Douglas-fir. Natural enemies generally prevent them from becoming a serious forest pest. Webbing and branch defoliation caused by tiger moths is unsightly on ornamentals.
BIOLOGY:
Tiger moths produce one generation per year. Adult moths emerge from mid-July to
late August. Females lay clusters of light green eggs on needles and twigs of
host trees. Eggs hatch in 3-6 weeks. The small gregarious larvae are dark brown
to black and quite hairy. Groups of young feed on current needles and form webs
or tents enclosing a portion of the branch. Feeding continues through the fall
and larvae over winter in tents. Tents are usually located in the topmost
branches or on the trees’ south and west sides. Larvae will feed outside the
webbing on warm sunny days throughout winter, returning to the tent before
nightfall. By early spring, tents are large, conspicuous, and filled with masses
of dead needles.
As caterpillars reach their full growth, they feed alone
away from the tent, often migrating to another tree. Full-grown caterpillars are
about 1-1/2 (3.5-4 cm) inches long and covered with yellow-brown to dark brown
hairs that can cause a skin rash on people sensitive to them. In June, mature
caterpillars spin brownish cocoons of silk and body hairs. These cocoons are
attached to branches, limbs, and trunks of the host trees and occasionally to
debris on the ground.
CONTROL: Chemical insecticides and the bacterial insecticide, B. t. (Bacillus thuringiensis), are available but not usually necessary. Remove tiger moth infestations by simply pruning and destroying branches with tents while larvae are resting inside.
Tiger moth caterpillars.
Tiger moth tent.
Douglas-fir Tussock Moth
Orgyia pseudotsugata (McDunnough)
The Douglas-fir tussock moth is one of the most destructive pests on ornamental Douglas-fir, white fir, and blue spruce in New Mexico. Needles in the upper portion of infested trees may be completely removed after one or two years of feeding. In Southwestern forests, tussock moth outbreaks have generally been confined to overmature, multi-storied stands of white fir and Douglas-fir.
BIOLOGY:
Eggs
hatch from mid-May to early June and caterpillars feed on the current year’s
developing foliage. Young larvae are 1/8 to 1/4 inches (4-7 mm) long and covered
with long, thin body hairs that later develop into tufts. Because the female
moth is wingless, the primary means of dispersal from tree to tree is by
windblown larvae. Young larvae congregate on the tops of defoliated trees and
drop on silken threads that may be over 10 feet long. These threads eventually
break from the tree and give a ballooning effect to the larvae. If caught by a
strong wind, some larvae may be blown great distances. Many of the larvae will
never find a suitable host and perish during dispersal.
Mature larvae are up to 1-1/4 inches (31 mm) long and very
colorful. Behind the head are two long, dark tufts of hair that resemble horns
projecting forward. On the posterior is a longer tuft of hair projecting
backward. In the middle of the back are four dense, buff-colored tussocks. Short
hairs radiating from red, button like centers cover the rest of the body except
for the head and legs. Some people develop an itchy rash from exposure to the
frequently airborne caterpillar hairs.
Older caterpillars do the most damage. After they are about
half-grown, they feed on new and older foliage lower in the crown and farther
back on the branches.
Pupation occurs inside a thin, silk cocoon spun on the
undersides of branches from late July to the end of August. Adults emerge within
10 to 18 days, depending on temperature.
Wingless female laying eggs in frothy mass.
Mature larva.
The female moth has only rudimentary wings and cannot fly. She emits a chemical sex attractant and soon mates, If undisturbed, all of her eggs will be deposited in a single mass on top of the cocoon from which she emerged. From 150 to 300 eggs are laid in a dry, tough, frothy substance covered with hairs from the female’s body. Over wintering occurs in the egg stage.
CONTROL: Without some form of control, ornamental trees can be completely stripped of all needles and die. Both chemical and biological insecticides are registered for use against the Douglas-fir tussock moth. The microbial insecticide, B.t. (Bacillus rhuringiensis), can provide an effective alternative to chemical control although results have been variable. Early treatment and multiple sprays improve results. B.t. is a bacterium that produces a toxin lethal to many kinds of moth larvae. Spray it during dry weather on small larvae when the egg hatch is finished and leaf extension 40 to 50 percent complete. Chemical insecticides are also most effective when applied to the small larvae. Don’t use these chemicals near water or bee hives; they’re toxic to both fish and bees. Egg and larval parasites, a virus, general insect predators, and birds also help control outbreaks of this pest.
Cocoon on underside of branch.
Defoliation by Douglas-fir tussock moth often kills the top of the tree.
Western Spruce Budworm
Choristoneura occidentalis Freeman
The western spruce budworm is a serious forest pest that also damages ornamental and Christmas trees growing at higher elevations. The budworm attacks Douglas-fir, white fir, and spruce. Outbreaks are periodic and can last from several years to over a decade. Damage from budworm outbreaks includes tree mortality, top-killing, and growth loss. Defoliation in recreation areas is unsightly and camping and picnicking can be discouraged by large numbers of dispersing larvae.
BIOLOGY: Western spruce budworm moths are about an inch long (22 to 28 mm) and mottled gray to orange-brown in color. Eggs are laid on the undersides of needles throughout the crown of host trees from early July through mid-August. About 50 (range 15 -120) pale green eggs are laid in two or three rows. Like fish scales, each egg overlaps the preceding one. Hatching usually occurs within seven to 10 days.
Newly hatched larvae are often dispersed by the wind to other branches. After a few days, they seek over wintering sites under bark or cone scales, between needles, or in other protected spots on the tree. They emerge the next May and chew paths through buds or feed at the base of new needles on expanding shoots. As they feed, they produce a silk webbing that catches uneaten needles. These needle remnants dry, turn red, and make the tree look scorched. The final two larval stages may be 25 to 32mm long and account for most of the defoliation. As new needles become scarce, larvae disperse on silk threads to the under story or adjacent trees.
Pupation occurs from late June to mid-July and lasts about 10 days. Adult moths emerge between late June and early August, depending on locality and weather conditions.
Larvae hatching from egg masses on needles.
CONTROL: At least 40 species of insect parasites attack the budworm; however, when weather and stand conditions are favorable, artificial controls may be necessary to keep budworm populations in check on high value trees. Both chemical and biological insecticides are registered for use against the western spruce budworm. The microbial insecticide Bacillus thuringiensis (B.t.) provides an effective alternative to chemical control. B.t. is a bacterium that produces a toxin lethal to many kinds of moth larvae. Spray it on small larvae during dry weather. Chemical insecticides are also most effective when applied to early larvae. In forests, reduce budworm potential by thinning stands to remove Douglas-fir and white fir and by heavy regeneration cuts that favor the establishment of pine and aspen. Thinning to reduce stand density will also increase vigor and reduce stress on remaining trees.
Infested, expanding shoot.
Conifer Sawflies
Neodiprion spp., Zadiprion spp.
Conifer sawflies can be divided into two groups—the “spring” and “summer” sawflies. Spring species generally feed on old needles so the new foliage remains and trees are never completely defoliated. However, summer sawflies feed on new needles first and then attack older needles. Defoliation by summer sawflies results in greater growth loss and more frequent tree mortality.
BIOLOGY: Adult sawflies are wasp like insects less than a half inch (11mm) long. The female uses a saw like ovipositor to cut slits into needles where eggs are laid. Most sawfly larvae feed in groups of 50 or more. Young larvae skeletonize the needles. Older larvae consume needles entirely. Larvae resemble caterpillars but have six or more pairs of abdominal prolegs and one pair of eye spots on the head. There is wide variation in color; many species are dark green or black.
Typicalsawfly feeding damage.
CONTROL: Since the insects feed in colonies, simply wash the larvae off with a high pressure hose, prune infested branches, or pick the larvae off by hand. For larger outbreaks, you may need to use a registered insecticide.
Adult female sawfly and eggs laid in slits on needle.
Gregarious sawfly larvae clustered around branch.
Conifer Aphids
There are
many species of conifer aphids in New Mexico that attack pines, true firs,
Douglas-fir, and spruces. Many of these are specific to a particular genus of
tree, some even to a particular species. Conifer aphids are rarely a concern in
the forest but often an annoying pest on ornamentals around homes. Heavy
infestations cause foliage to yellow and stunt the growth of young trees. Needle
growth is reduced, twigs dry, and heavy defoliation occurs with excessive
feeding. Occasionally, even larger trees are so weakened that they die in a few
seasons or are attacked by other insects.
Aphids feed by piercing the bark of branches and twigs and
sucking out large amounts of sap. Because they can’t use all of the liquid
portion of the sap, they expel much water, sugar, and other compounds. This
sweet, sticky substance is called honeydew and is often covered with a black
fungus called sooty-mold. Ants, bees, and wasps are attracted to the honeydew.
When aphid populations are high, honeydew rains down, covering lower branches
and objects below the tree. Sometimes it appears as though the tree and adjacent
area were sprayed with crude oil.
Aphid eggs on ponderosa pine needle.
Cinara spp.
Spruce aphid defoliation on Colorado blue spruce.
BIOLOGY: Most species are quite large for aphids, up to 1/4 inch (6mm), and are generally dark in color. In the fall, females lay shiny, black eggs that resemble very tiny jelly beans on the twigs and needles. Eggs hatch in the spring and the females soon begin producing live young without mating. There are a number of generations per year with both winged and wingless forms.
CONTROL: Several chemical pesticides and insecticidal soaps effectively control conifer aphids. The timing of spray application or other chemical control measure isn’t as critical to successful control as with other insects. Damaging populations should be present before taking any control action. Low populations are effectively controlled by a host of natural enemies.
Aphid on spruce branch.
Cooley Spruce Gall Adelgid
Adelges cooleyi (Gillette)
Cooley spruce gall adelgid is the most common gall-forming adelgid on spruce in New Mexico. The galls are cone-shaped or pineapple-shaped. The insect is not usually considered a forest pest, but is often troublesome on ornamental spruce and in Christmas tree plantations where large numbers of galls are aesthetically damaging. Galls don’t seriously affect overall tree health.
BIOLOGY: Generally, winged females fly from Douglas-fir to spruce where they lay eggs at the bases of newly expanding buds in early spring. Nymphs hatch from eggs and begin feeding at the bases of growing needles. In response to chemicals injected by feeding nymphs, the tree quickly envelops the insects in rapidly developing galls. Young galls are green to purple and become purplish or reddish brown with age. Galls contain 50 to 350 nymphs and are usually from 1 to 3 inches (25-75mm) long. In mid-July, galls begin to dry and open, allowing the full-grown nymphs to crawl out to the needles. Nymphs molt into winged adults and fly back to Douglas-fir to lay eggs. This generation of nymphs secretes a waxy, woolly covering over their bodies as they feed. The insects look like little balls of cotton clinging to needles. Occasionally, heavy infestations on Douglas-fir will look like snow on the tree. Feeding causes yellow spots on the needles and may cause distorted needles. Eventually, another winged form is produced that migrates back to spruce, completing the life cycle.
Alternate life-stage or "wolly aphid” ~ Douglas-Fir.
Galls on spruce.
CONTROL: There are insecticides to control the adelgid; however, timing of the spray is difficult to determine for effective control. Dormant oils applied before buds swell have effectively controlled the overwintering stages. However, there is a risk of injuring or discoloring foliage when using oils. On small ornamentals, prune off galls before adults emerge. It may also help to plant spruce or Douglas-fir exclusively, rather than planting the species together.
Spider
Mites
Oligonychus
spp.,
Tetranychus spp.
Although these tiny arthropods have six legs when they hatch from the egg, they’re not insects. After molting once, they become eight-legged. There are a number of species that may be green, yellow, orange, or red, often with dark pigmented patterns. Spider mites feed on a variety of conifers but are most likely to be a problem on spruce and juniper. Feeding symptoms resemble those of aphids and scales — spotting, yellowing, and premature dropping of needles. Webbing and associated eggs, cast skins, and live mites are also characteristic. The webbing can become obvious if it becomes covered with dust.
The spruce spider mite, Oligonychus unungius (Jacobi), and the two-spotted mite, Tetranychus urticae (Koch), appear to be the primary species found in New Mexico.
CONTROL: Wash the plants with a strong stream of water to remove many of the mites and help keep the population in check. For large plantings, there are a number of miticides registered as well as insecticidal soaps, and dormant and summer oils.
BIOLOGY: Spider mites have piercing-sucking mouth parts and damage trees by sucking plant juices from needles. Numerous generations can be completed in a single year and the population can explode in hot, dry conditions in the absence of natural enemies.
Comparison of clean (left) and mite infested, dusty foliage.
Close-up of spider mite and eggs.
Pine Tip Moths
Rhyaciona spp.
There are at least eight different species of pine tip moths in New Mexico. All species mine in the buds and terminal shoots. Injury is most severe on trees under 1 2 feet tall that may be stunted or deformed by heavy infestations. Hosts include ponderosa, pinyon, eldarica (Afghanistan), and other pines.
BIOLOGY: Most species have one generation per year; the Nantucket pine tip moth has two to four generations. Eggs are laid on new shoots or terminal buds from March through June depending on the species. Newly-hatched larvae feed for a short time at the bases of needles. They then bore into buds, laterals, and terminals, and mine out the pith from the tip down to the base of the shoot. The point of attack is marked by a small resin flow, but no pitch nodule is formed. The larvae are yellow to orange to brown and are 1/2 to 3/4 inches (10 to 20mm) long when full-grown. Tip moths, depending on the species, over winter as pupae in the tips or shoots, in bark crevices, or in litter below the tree.
CONTROL:
Heavily
attacked ornamentals may require insecticide control. Timing of control is
critical for success. Control the newly hatched larvae before they bore into the
shoots. Use pheromone traps to monitor moth populations to determine times of
peak egg-laying.
The southwestern pine tip moth, which is common in northern
New Mexico, can be reduced by destroying the over wintering pupal stage. Pupae
of this species are found attached to the root collar of the tree in plaster
like cocoons.
Damage to pine shoot.
Severely clamageaponderosa pine.
Nantucket pine tip moth adult.
Pinyon Pitch Nodule Moth
Petrova arizonensis (Heinrich)
Pinyon pitch nodule moth attacks pinyon pines throughout New Mexico. Attacks are characterized by fading branch tips and nodules of pitch formed at the insect’s feeding sites. The pitch nodules are hollow balls of pitch 1/2 to 1 inch (10-25mm) long, round, smooth, and often light purple or red. They’re most often found at the crotch of two or more twigs. The fading twigs eventually lose their needles and fall off. Leaders are occasionally damaged and forked trees may result.
BIOLOGY: The pinyon pitch nodule moth has one generation per year. The small, rusty-brown moths emerge through holes in the pitch nodule in late June and early July. Eggs are laid on needle sheaths of the current year’s growth. Newly hatched larvae feed on young needles before boring into the bark at nodes or whorls of twigs or branches. Full-grown larvae are about 1/2 inch (10mm) long, reddish yellow with a black head and a dark area behind the head. Pupation occurs inside the pitch nodule in June. Pupae move just below the surface of the pitch before they emerge as adults.
CONTROL: There are no registered insecticides to control this insect. In the forest, top-killing of pinyon is rarely important. On valuable ornamental trees, control the insect by pruning and destroying the infested tips as they fade in May or early June before the adult moths emerge. On branches and stems, destroy larvae by crushing them within the pitch nodule.
Reddish-brown “pitch nodule4 and fading needles characterize new attack.
Dead tips and crusty pitch nodule with adult exit hole.
Spittlebugs
Aphrophora spp.
Clastoptera spp.
Spittlebugs feed on many conifer species in New Mexico but those found on juniper are most often noticed. The insects are characterized by spittle like froth produced by feeding nymphs. The insect’s feeding causes no significant damage to forest or ornamental trees. Scattered twig mortality may be seen in the crown of infested trees.
BIOLOGY:
Adult spittlebugs (froghoppers) are very active and superficially resemble
leafhoppers. Most species lay eggs in midsummer in rows on the foliage. Eggs
hatch the following spring. Nymphs of some species drop from the trees and feed
on under story shrubs while those of the juniper spittlebug remain on the trees.
Nymphs are soft-bodied and white to brown. As they feed, they
produce masses of “spittle” by internally blowing air through a viscous sugar
solution and releasing froth through the anus. The spittle serves both as a
protective device and as a means of reducing evaporation. Nymphs shed their skin
five times before molting into winged adults. Adults continue to feed all summer
on sap from twigs but do not produce a spittle mass.
CONTROL: Spittlebug injury isn’t serious in New Mexico and doesn’t warrant control, but spittle masses on ornamentals can be unsightly. Use a strong stream of water from a garden hose to dislodge nymphs and wash away the spittle masses.
Juniper spittlebug spittle mass.
Bark Moths and Pitch Moths
Dioryctria spp. and Vespamima spp.
Bark moths and pitch moths have similar habits and effects on trees. Pinyon pine is the primary host in New Mexico, although ponderosa pine and occasionally Douglas-fir and the true firs are attacked. Larger branches, limbs, and trunks of young trees are attacked. Repeated attacks can seriously weaken trees and kill branches. The most severe damage is to trees under 20 feet, especially in urban areas. The insects are rarely a problem on larger trees or in the forest environment. Pitch moth attacks appear as large, ugly masses of pitch that form at the wound site. Bark moth attacks typically produce less pitch.
BIOLOGY: Pitch moths (Vespamima spp.) require two years for one generation and over winter as larvae each winter. Bark moths (Dioryctria spp.) require only one year for a generation and over winter as eggs or larvae. Eggs are laid in bark crevices or near mechanical wounds on the bark. Newly hatched larvae tunnel under the bark, forming irregular galleries or elongated gouges in the sapwood. Pitch moth larvae feed on pitch the tree produces in response to their tunneling. Oozing pitch masses 1 to 3 inches (25-75mm) in diameter cover entry holes and conceal larvae and their destructive tunneling. Full-grown larvae are 3/4 to 1 inch (15-25mm) long, dirty white, yellow, orange, light green, or light brown. Bark moth larvae feed on the inner bark and when full-grown, are marked with rows of dark spots.
Pitch moth attack on the underside of pinyon branch.
Fresh pitch moth attack on pinyon.
CONTROL: No insecticides are registered for use on these insects. The only effective control is removing larvae from the pitch mass or from under the bark with a knife or similar tool. Avoid pruning or mechanical injury to the bark during the summer months when adult moths are seeking egg laying sites.
Bark moth larva mining under ponderosa pine bark.
Twig Beetles
Pityophthorus spp., Pityogenes spp.
Twig
beetles are frequent pests of pines and occasionally spruce and other conifers.
In forests, they attack shaded-out and storm-damaged twigs and branches.
Occasionally, high beetle populations develop in drought-stressed, injured, or
recently felled trees. Generally, breeding is restricted to twigs and small
branches, but larger branches and thin barked portions of the trunk of stressed
trees may be attacked. In urban areas, recently transplanted pines may be killed
by trunk infestations.
Trees attacked by twig beetles can be identified by fading branches throughout
the crown. Tan sawdust is produced around the attack site. On smaller twigs and
branches, most of the cambium will have been mined beneath the bark. Small,
star-shaped egg galleries can be seen under the bark on larger branches and
small trunks.
BIOLOGY: Adult twig beetles are 1/16 to 1/8 inch (1.5 to 3.0mm) long and dark brown. Most species have rounded rear ends but a few have a pair of short spines. The larvae are fat, white, “C”-shaped grubs with light brown heads. Most species have 2 to 4 generations per year, depending on local conditions.
CONTROL: Control infestations of twig beetles by hand-pruning infested twigs and branches and by keeping trees vigorous with supplemental food and water.
Twig beetle damage to pinyon tips.
Tiny exit holes on pine twigs and branches.
Bark Beetles
Ips spp.
Dendroctonus spp.
Ips beetles, also called engraver beetles, attack ponderosa and pinyon pines as well as other conifers. Dendroctonus beetles attack medium to large ponderosa pine, blue spruce, Engelmann spruce, and Douglas-fir trees in New Mexico. Different species within the genera are difficult to distinguish based on body shape alone. Host species attacked, location, and shape of tunnels (egg galleries) they excavate are all important clues in identifying the pest species.
Ips adult.
Dendroctonus adult.
Full-grown bark beetle larvae and pupae. Note blue stain to wood caused by introduced fungus.
BIOLOGY: Details of the life cycle vary with each species but some generalizations can be made. Initial attack on a tree is made by a few adult beetles. Once a tree is selected, the beetles produce an “aggregation” pheromone, drawing many beetles to the tree. The attack on the tree may be initiated by the male (i.e. Ips spp.) or by the female (i.e. Dendroctonus spp.) beetle. The beetle chews through the bark and excavates a chamber in the moist tissue beneath the bark. The opposite sex then enters the chamber and mating occurs. The female beetles then excavate distinctive tunnels or egg galleries under the bark. Eggs are laid in niches along the lateral walls.
Boring dust at the base of a tree.
Adult beetles may introduce a number of microorganisms to
the tree when they attack. Some species have evolved specialized pockets for
carrying such microorganisms as fungi, yeasts, and bacteria. Introduced
blue-stain fungi are particularly important in killing the tree and may provide
nutrition for the developing brood.
After hatching, larvae bore away from the egg gallery at
right angles. They molt three or four times and then construct a pupal cell
either in the phloem or in the bark.
Bark beetles usually attack severely weakened or damaged
mature or over mature trees. Trees damaged by lightning or harsh weather and
trees stressed from transplanting, logging slash, and recently cut firewood are
prime candidates for bark beetle colonization. Vigorously growing trees have
active resin systems that deter such colonization. When the beetle bores into a
healthy tree, resin exudes through the wound and may prevent the beetle’s entry.
The resin may also inhibit spread of the fungus that aids the beetles in killing
the tree. When populations of bark beetles are very high, particularly around an
outbreak, trees may be attacked by so many beetles that even healthy trees
succumb.
Time between generations varies considerably for different
species of bark beetles. Some species of Ips can complete their life cycle in
six to eight weeks during warm summer months. Others require two years for a
single generation, such as the spruce beetle (Dendroctonus rufipennis
Kirby), which lives at high elevations. Most species will have one or two
generations per year.
Ips gallery showing central mating chamber and radiating egg galleries.
Pitch tubes from Dendroctonus
SYMPTOMS: Foliage high in the tree begins to fade, turning from green to yellow or red after the tree has been attacked. Boring dust, a sawdust-like material pushed out of beetle galleries, can often be found around the base of the tree, in bark crevices beneath entrance holes, and on tops of branches where they intersect the trunk. Globules of resin called “pitch tubes”, produced as the tree’s defense, may or may not be present. Woodpecker activity on the trunk is also a good indication that the tree has been attacked.
PREVENTION AND CONTROL:
Once a tree has been successfully colonized by bark beetles, it cannot be saved. Infested trees should be removed, burned, or buried as soon as possible to protect surrounding trees from attack by emerging beetles.
Fading crowns of bark beetle infested trees.
Check green firewood for bark beetles. Bark beetles emerging from infested firewood account for many tree losses near homes and in urban settings. If firewood has been stored for at least one season, the beetles won’t be present. Green firewood collected or purchased in summer when temperatures are high should be stacked in direct sunlight and covered with clear plastic. Don’t use black or other opaque plastic because it prevents sunlight from entering. Piles should be no larger than 4x4x4 ft. or 1/2 cord. The edges of the plastic should be buried in the ground. This creates a greenhouse effect, raising temperatures under the plastic up to 160 degrees (F). After two or three weeks of sunny weather, the beetles should all be dead. Bark beetles can also be prevented or controlled in firewood by peeling off the bark. This exposes the phloem, rendering it useless to the beetles. The method is difficult but effective.
Green firewood piles are often bark beetle breeding grounds.
Green firewood should be stacked in the sun and covered with clear plastic.
Roundheaded and Flatheaded Wood Borers
Family Cerambycidae Family Buprestidae
Roundheaded and flatheaded wood borers attack recently dead and dying trees, often riddling them with tunnels. In the forest, they become especially numerous after fires. Roundheaded borers are often the most destructive, tunneling deep into the wood. Fresh-cut logs left in the forest or in storage for a year can be seriously damaged. These beetle larvae can often be heard chewing in infested firewood or vigas. Adults feed on cambium of twigs and small branches and on needle bases. Shoot tips occasionally flag above adult feeding sites. Adult feeding damage can be heavy along edges of recent clear cuts, in groups of seed trees left in clear cuts, or in residual blocks of timber left in harvested areas.
BIOLOGY: Generally, the life cycle is complete in at least two years. Eggs are laid in slits in the bark throughout the summer. Young larvae feed on wood beneath the bark, creating tunnels filled with frass and wood chips. In late summer, they tunnel deeper into the wood and over winter. The next year they continue tunneling through the wood. Full-grown
Adult roundheaded borer, a long-horned beetle.
roundheaded larvae are legless, with cylindrical, segmented bodies. Flatheaded larvae are similar but are broad and flat behind the head. They pupate at the end of a tunnel beneath the bark. Adults emerge through circular (roundheaded) or oval (flatheaded) holes cut in the bark and feed on needles and tender bark of twigs.
CONTROL: Wood borer damage to logs cut for lumber or vigas can be prevented by using wood soon after cutting it. Other guidelines for preventing damage are as follows:
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Before spring, remove wood cut in the winter from the stand.
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When storing wood in the forest, piles should be as large as practical and a long distance from cutting areas.
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Wood cut in summer should be used immediately.
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Wood stored in the forest in summer should not be stored in the mill wood yard.
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Wood piles in the wood yard should be as large as possible.
Cross-section of borer infested log.
Western Cedar Borer
Trachykele blonde/i Marseul
Western cedar borer is an aggressive pest of juniper and Arizona cypress in New Mexico. It belongs to the buprestid beetle group also known as metallic or flatheaded wood borers. Unlike most other buprestids, the western cedar borer will attack and seriously injure or kill seemingly healthy trees. Considerable damage is found in some juniper stands; older, larger trees appear to be favored by the beetles. Larval galleries degrade lumber from logs, making them useless for products requiring sound wood, such as furniture.
Cross-section of damage.
BIOLOGY: Adults range from 1/4 to 1/2 inch (11 to 17mm) long and are bright emerald with several dark areas on the wing covers. Females lay eggs under bark scales on branches of living trees. Flatheaded larvae bore from branches into the main bole. They feed primarily in the heartwood for several years. Full-grown larvae move near the surface and pupate. Adults emerge in the spring, leaving oval or rectangular exit holes in the tree.
CONTROL: No practical controls or preventive measures have been developed for this insect pest.
Adult exit hole.
Juniper Twig Pruner
Styloxus bicolor (Champlain and Knull)
Juniper twig pruner causes twig dieback on junipers and Arizona cypress growing throughout New Mexico. The insect is a small cerambycid or long-horned beetle.
BIOLOGY: The juniper twig pruner adult is 1/4 to 1/2 inch (7 to 11mm) long and has a reddish-orange head and brownish to black body. Eggs are laid on branches, often near an intersection of twigs, one to two feet from the branch tip. Larvae are small, white, cylindrical, legless grubs that kill twigs by boring through the centers. The life cycle may take as long as two years to complete.
CONTROL: No chemicals are registered for control of this pest. Damage can be unsightly when populations are high but trees are rarely seriously injured by the juniper twig pruner.
Juniper twig pruner damage.
Cross
section of injured twig.