The Bugwood Network

Insect Pests of Christmas Trees

Shoot, Limb and Trunk Pests

Pine Tip Moths

Tip moths are the most serious insect pests attacking Christmas trees in Georgia. Two species commonly occur; the Nantucket pine tip moth Rhyacionia frustrana (Comstock), and the pitch pine tip moth, R. rigidana (Fernald). The Nantucket pine tip moth is the most common pest. They attack loblolly, shortleaf, Virginia pine and other pines except white pine.

Description - Adults are small (9 - 15 mm wingspread) gray moths with brick-red to brownish patches on their wings (Fig. 1). Fully grown larvae are orange-brown and about 10 mm long.

Damage - Injury is caused by larvae tunneling in new growth, buds and shoots. Infested twigs die, resulting in loss of main-stem terminals, poor tree shape, and poor tree growth.

Life History and Habits - Tip moths pass the winter as pupae inside infested tips (Fig. 2). Adults begin to emerge with the first warm days of spring. Emergence has been recorded as early as late January in south Georgia, but the first significant emergence is usually in late February or early March. It often continues through April.

Figure 1. Nantucket Pine Tip Moth Adult.
Figure 1. Nantucket Pine Tip Moth Adult.

Adults are rarely seen during the day, being most active at night, dawn or dusk. A few days after emerging, moths mate and begin laying eggs on needles, in needle sheaths, on developing tips or on buds. First generation eggs normally hatch 25 - 30 days after the moths emerge. Newly hatched larvae feed on the bases of needles (Fig. 3) and often construct delicate webs in needle axils or between buds and needles.

Figure 2. Nantucket Pine Tip Moth Pupal Case and Damage.
Figure 2. Nantucket Pine Tip
Moth Pupal Case and Damage.
  Figure 3. Nantucket Pine Tip Moth Larva Feeding at Base of Needles.
Figure 3. Nantucket Pine Tip Moth
Larva Feeding at Base of Needles.

After molting, the second instar larvae bore into and consume buds. A bead of resin exuding from a bud is often the first sign of larval entry (Fig. 4).

As they grow and develop, each larvae continues to feed within the bud and shoot, boring down the center of the shoot after it has consumed the bud. Eventually, infested tips turn brown and die.

The larval period lasts two to four weeks, and pupation occurs within infested tips. The pupal stage lasts one to

Figure 4. Resin Droplet on Bud Indicating Entry of Tip Moth Larvae.
Figure 4. Resin Droplet on Bud Indicating
Entry of Tip Moth Larvae.
two weeks; then moths emerge to begin the cycle again. There are usually four generations per year in south Georgia, and three in north Georgia. Developmental time depends largely on temperature.

Control - Tip moth suppression in commercial Christmas tree plantings requires chemical controls. Time sprays to kill the small, newly hatched larvae when they are exposed on the outside of shoots (before they penetrate the buds). Larvae are most vulnerable immediately after egg hatch. Sprays can best be timed by monitoring adult emergence with pheromone traps, recording daily maximum - minimum temperatures and predicting egg hatch using a temperature "degree-day" program. This technique was described by Gargiulllo, et.al. (1983, 1985). An alternative method is to monitor adult emergence from pupal cases. When empty pupal cases are found in terminals, moths have emerged and egg-laying can be expected within a predictable range of days.

First Adult
Emergence
  Expected First
Egg Hatch
Generation 1 ......................... 25 - 30 days
Generation 2 ......................... 10 - 20 days
Generation 3 ......................... 5 - 10 days
Generation 4 ......................... 10 - 15 days

This method of determining egg hatch requires careful, frequent, and accurate monitoring of adult emergence from pupal cases within the tips.

Dioryctria spp.

Several moth species of the genus Dioryctria injure Christmas trees in Georgia. They are variously called coneworms or pitch moths. One of the more common is D. amatella (Hulst.). They attack almost all species of Southern pines.

Description - The forewings of the adult moth are dark gray-brown to black, marked with patches and zigzag lines of white. The wingspan is 25 - 30 mm. Mature larvae are greenish-white underneath and reddish-brown to almost black on top. They are about 25 mm long.

Damage - Overwintering larvae may attack buds or elongating terminals in the spring, causing death or distortion of tips. Later, larvae attack second-year cones or enter damaged areas on the limbs or tree trunk. Pitch masses containing frass (worm droppings) normally mark

Southern pine coneworm larva and adult on loblolly pine cone, a seed orchard pest.
Southern pine coneworm larva and adult
on loblolly pine cone, a seed orchard pest.
infestation sites. Mechanical wounds such as pruning scars and fusiform rust galls are favorite places of attack. When larvae attack woody portions of trees, they feed beneath the bark and can girdle and kill small trees.

Life History and Habits - Dioryctria usually overwinter as young larvae at the base of first-year cones, in fusiform rust galls or under expanded terminal needles. Older larvae may also occasionally overwinter in second-year cones or in galleries under bark. Adult moths emerge in the spring and lay eggs on shoots, tree wounds or cones. Larvae normally feed, mature, and pupate in the original infestation site but may occasionally migrate to new feeding sites as the develop. They usually pupate in the resinous mass associated with feeding. Developmental time varies depending on several factors; there may be one to four generations a year.

Control - Tip damage by overwintering larvae can be suppressed by an early spring insecticide application. Where a problem is known to exist, spray as soon as trees begin to grow in the spring. Spray infestations of woody portions of trees with a recommended insecticide. If only a few trees are infested, the larvae can be removed and destroyed by hand.

Black Turpentine Beetle

The black turpentine beetle, Dendroctonusterebrans (Oliv.), ranges over most of the eastern United States and attacks all species of Southern pines. They cause occasional problems in Christmas tree plantings, especially on damaged or recently pruned trees near woods or freshly cut timber stands.

Description - Adults are dark, reddish-brown to black beetles, 5 - 10 mm long. Elytra (wing covers) are entire, with scooped-out area at the rear. They are the largest of the bark beetle species in Georgia. Larvae are white to cream-colored, about 12 mm long, marked with brown tubercles along each side of the body.

Damage - Adults puncture the bark and larvae feed on the inner bark. Resin flows out of the entrance holes, and mixed with boring dust, forms large reddish to whitish pitch tubes. Pitch tubes are often the first indication of attack (Fig. 5). Only a few beetles may kill sections of the inner bark. Heavy infestations, where larval tunnels overlap, can girdle and kill small trees.

Life History and Habits - All life stages may be present throughout the year in the deep South. Eggs are laid in the basal parts and large roots of weakened or dying trees and

Figure 5. Black Turpentine Beetle Pitch Tube.
Figure 5. Black Turpentine Beetle Pitch Tube.
in freshly cut stumps. Freshly cut stumps are preferred for breeding. Adults excavate an egg galley up to 1 inch wide and 20 inches long underneath the bark on the face of the sapwood. They deposit eggs in a linear group of 50 to 200 eggs on one side of the gallery. Eggs hatch in about 10 days, and the white, grub-shaped larvae feed into the phloem, excavating large often fan-shaped galleries. Larval feeding lasts five to seven weeks. Pupation occurs within pupal cells in corky bark or between bark and wood. The pupa stage lasts 10 - 14 days. Adults emerge through holes chewed in the bark and fly to trees or stumps to start a new generation. Several adults may emerge through a single hole. The life cycle takes two and a half to four months depending on the temperature. There are tow to three generations per year.

Control - Infestations can often be avoided by quickly removing injured, dead or felled timber near Christmas tree plantings. Spraying stumps of timber cut near plantings will also reduce chances of infestation by reducing breeding sites. If infestations become established in Christmas trees, thoroughly spray infested trees and surrounding trees with a recommended insecticide.

Pales and Pitch-Eating Weevils

The pales weevil, Hylobius pales (Herbst), and the pitch-eating weevil, Pachylobius picivorus (Germar), can be very destructive pests of young pines. All species of pines are considered susceptible to damage, and either insect may be an occasional pest of pines grown as Christmas trees.

Description - Adults of the pales weevil are 6 - 10 mm long, black to reddish-brown, with patches of yellow hairs appearing as bars across the wing cover. Pitch-eating weevils (Fig. 6) are slightly larger (10 - 12 mm) and brownish-black with yellowish spots on the wing covers.

The larvae of both species are typical weevil grubs. They are white with brown heads, legless and somewhat C-shaped. Mature larvae are 6 - 7 mm long.

Damage - The most serious injury occurs to small seedlings or to the branches of larger trees as a result of adult feeding. The weevils feed by chewing small, irregular holes in the bark. When feeding is heavy, the holes run together, effectively girdling small trees or the branches of larger trees. Even if the terminals of larger trees are not

Figure 6. Pitcheating Weevil Adult.
Figure 6. Pitcheating Weevil Adult.
girdled, "flagging" or distorted terminals can result, making the tree less marketable. Damage is usually more serious in or near freshly cut timber areas.

Life History and Habits - In extreme south Georgia, adults may be active year-round, although numbers are normally low in winter. Adult weevils may also pass the winter in the soil or beneath ground litter around a tree. On emerging in the spring, adults feed on the bark of pine seedlings or the terminals and twigs of larger trees. Trees up to ½ inch in diameter are sometimes girdled and killed. The weevils usually feed at night and hide in the soil around trees during the day. Adults are attracted to freshly cut stumps or weakened pines. Females lay eggs beneath the bark, in the roots of stumps, dead trees or dying trees. Larvae hatch and feed primarily in the roots for six to eight weeks before pupating. The pupal stage lasts two to four weeks, depending on temperature. There are thought to be two generations per year in south Georgia.

Control - Adult feeding damage may be prevented by spraying young seedlings and twigs with an insecticide when adults emerge in the spring. Exact timing is best determined by examining twigs or terminals fro the small circular feeding holes which denote adult activity. Sprays may also be needed for adults emerging during the summer.

Avoid attacks by not planting Christmas trees in or near recently harvested areas and by quickly destroying stumps and weakened dying trees in or near plantings. If planting near a recently cut area cannot be delayed, dip young seedlings in an insecticide before planting to protect them against the weevils. If stumps cannot be pulled, treat them with an insecticide to reduce egg-laying by the adults.

White Pine Weevil

The white pine weevil, Pissodes strobi (Peck), occurs throughout the eastern United States. Its most common host is the eastern white pine, but it also attacks Norway spruce, Scotch pine, and pitch pine, among others. In Georgia, it is a problem only in the northern part of the state.

Description - Adults are elongate, brownish weevils, 4 - 6 mm long, marked irregularly with gray-white patches. They look much like other Pissodes weevils, such as the deodar weevil (Fig. 7). Larvae are creamy white, cylindrical, legless grubs.

Damage - Adults and larvae feed on terminal shoots. The first evidence of attack in the spring is excessive pitch flow from feeding punctures on the preceding year's terminal shoots. Later, new growth

appears stunted, wilts and dies. Trees up to three feet tall may be killed. Dead terminals on older trees are usually replaced by one or more laterals, resulting in crooked or forked trees.


White pine weevil damage. Dead terminal caused by damage.
White pine weevil damage.
Dead terminal caused by damage.

White pine weevil adult.
White pine weevil adult.
 

Life History and Habits - Adults overwinter in litter under the trees. They emerge in the spring (about March) and feed on the succulent trinal leaders. Eggs are aid in small punctures in the bark of the terminal and hatch in 7 to 10 days. Larvae bore downward side by side, feeding on inner bark and outer wood of the terminal. This feeding girdles and kills the leader. Mature larvae pupate in chambers formed in the wood. Adults normally emerge in about two weeks, although they may emerge throughout the summer. Emerging adults feed on old and mature new growth, Only one generation per year has been reported.

Control - In the spring, check new terminal growth closely for sign of injury. In areas of known infestation, apply control measures early (March and April) to protect new terminals from injury by emerging adults. Treatments may also be needed in late summer to early fall for newly emerging adults.

Deodar Weevil

The deodar weevil, Pissodes nemorensis Germar, attacks most species of pines and many introduced cedars in Georgia. It is normally not as serious a pest as some other weevil species, but high numbers can cause serious damage.

Description - The adult weevil is about 6 mm long, grayish-brown to dark brown with whitish spots on its wing covers (Fig. 7). Larvae are C-shaped, creamy white and legless, with brown heads.

Damage - Adults chew holes and feed on the inner bark and wood of twigs and leading terminals. Larvae feed beneath the bark much like the white pine weevil. A swelling of the bark over the feeding area may denote the presence of larvae. Dead or dying seedlings or terminals are often the first symptom of attack.

Life History and Habits - Adults are attracted to weakened, stressed or dying trees. They often breed in logging slash and trees killed by bark beetles. If cutting is done near Christmas tree plantings, the risk of infestation is increased. Eggs are laid in niches in the inner bark of laterals and terminals through holes chewed by adults.

Figure 7. Deodar Weevil Adult.
Figure 7. Deodar Weevil Adult.
  Figure 8. Deodar Weevil Pupa in Chip Cocoon.
Figure 8. Deodar Weevil Pupa in Chip Cocoon.

Eggs hatch in one or two weeks, and larvae feed on the inner bark cambium. The larvae feed for about six weeks, then pupate in small, chip cocoons in the wood (Fig. 8). The pupal stage lasts two to six weeks. Development time depends on the weather. There are probably two generations per year in Georgia.

Control - Attacks can be avoided by keeping trees as healthy and vigorous as possible and by being careful not to injure or damage trees during normal operations. If weevil damage is found, treat infested trees and surrounding trees with insecticide to prevent further infestation.

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Last updated on Wednesday, December 02, 2015 at 09:52 AM
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