The Bugwood Network

Insect Pests of Christmas Trees

Sucking Insects

Pine Needle Scale

Pine needle scale, Chionaspis pinifoliae (Fitch), is found on a variety of conifers throughout the United States. It attacks several species grown as Christmas trees.

Description - The waxy covers of mature females are white, elongate, about 3 mm long and usually wider toward the back end. Male covers are also white and slender but are only about half the length of the females. Crawlers (immature scales) are very small, somewhat oval and reddish to straw-colored.

Damage - The scale sucks sap from the needles, causing yellowish, then brownish discoloration. Heavy infestations may result in needle drop, loss of vigor and twig death. Infestations are usually easy to identify because the mature white scales stand out against the green needles (Fig. 13). Scales may infest a single limb or the entire tree.

Life History and Habits - In cold years, the eggs spend the winter under the scale coverings of dead females. During warm winters, especially in south Georgia, crawlers (immature scales) and adults may be present year-round.

Figure 13. Pine Needle Scale.
Figure 13. Pine Needle Scale.
Crawlers hatch from the eggs, emerge from beneath the mothers' scale coverings and move to new areas on the needles. There they settle down, begin to feed and form their own scale coverings. Crawlers are spread from tree to tree by wind, other insects, birds or mammals. Later, winged males emerge from beneath their coverings fly to the females and mate. Females remain under their scale coverings throughout their lives, laying eggs beneath the covers. There may be several generations each year.

Control - The scales can be controlled by insecticide sprays directed at the exposed crawler stages. Careful monitoring of emerging crawlers of emerging crawlers is required to pinpoint emergence peaks and properly time sprays. Also apply oil sprays, to kill overwintering forms, just before new growth begins in early spring. A two percent superior oil solution ( 2 gals. 70-sec superior spray oil over per 100 gals. water) is normally suggested. The oil kills by suffocation, so complete coverage of infested trees is critical.

Pine Tortoise Scale

The pine tortoise scale, Toumeyella parvicornis (Cockerell), and similar, closely related scales such as the striped pine scale, are frequently a serious problem in Christmas tree plantings. They attack Virginia pine and various other pine species.

Description - Mature female scales are brown, about 6 mm long, roundish-oval and convex (Fig. 14). They resemble small tortoise shells – hence their common name. Male scales are smaller, whitish, elongate and flat. Mature males are tiny, somewhat oval, orangish to reddish and may develop a powdery substance on their margins soon after hatching.

Damage - The scales infest twigs and branches feeding on plant juices. Feeding injury results in yellowing of needles and reduced growth. Heavy infestations can kill branches or even entire trees. The first sign of a heavy scale population

Figure 14. Pine Tortoise Scale with Honeydew and Sooty Mold on Needles.
Figure 14. Pine Tortoise Scale with
Honeydew and Sooty Mold on Needles.
is often black-looking trees. The insects excrete a sugary substance called honeydew, which supports a black sooty mold fungus that may partially or entirely coat infested trees interfering with photosynthesis. The honeydew is also very attractive to bees and ants, which use it as food.

Life History and Habits - Depending on location, weather conditions and the season, the pine tortoise scale may be found year-round in all life stages or may overwinter as immature females on twigs and branches. In most of Georgia, the scale has an overwintering phase but in extreme south Georgia it is sometimes possible to find crawlers during warm periods in winter. When mature, each female lays several hundred eggs. The eggs hatch within a few days, beneath her scale covering. Crawlers emerge, move about for a day or two, then settle and begin feeding on new growth. The crawlers may emerge over several days. Once they settle and begin to feed, they go through a series of molts and develop their own scale coverings. Small winged males emerge from under their coverings, seek out females nas mate. There are several generations per year. Four distinct crawler emergences commonly occur inmost of Georgia between April and October.

Control - Heavy infestations of pine tortoise scale are often wiped out by various species of lady beetles. Avoid unnecessary chemical applications for all insects to conserve these lady beetles. If pine tortoise scale controls are needed, they are the same as for pine needle scale. Inspect trees regularly throughout the growing season to pinpoint crawler peaks. Adult scales are very hard to control with insecticide sprays, but the exposed crawler is relatively easy to kill. It's especially important to control the first crawlers t emerge in the spring because controls for first emergence are easiest to time and you can reduce problems fr the remainder of the year. Mark infested trees and those nearby for superior oil sprays during dormancy. Two sprays are normally needed.

Aphids

Several kinds of aphids (Homoptera:Aphididae) may infest conifers grown as Christmas trees. The white pine aphid, Cinara strobi (Fitch), and others in the same genus, including C. pini (Linn.) and C. carolina Tissot, are sometimes a problem. Others include Eulachnus spp. and Essigella spp. The giant bark

aphid, Longistigma caryae (Harris), although not normally a pest of conifers, has also been found in Christmas tree plantings in late season.

Description - Depending on the species, aphids may be white, green, gray, black or brown. Some may have stripes or spots. All are usually small (1 - 6 mm long), soft-bodied and somewhat pear-shaped, and they may or may not have wings.

Most have rather long antennae and a pair of cornicles (tail-pipe-looking structures) on the fifth or sixth abdominal segment. Nymphs (immature forms) look much like the adults but are generally smaller and never have wings.

Damage - Aphids suck sap from the trees. Both nymphs


White pine aphid infestation.
White pine aphid infestation.
and adults do damage. Heavy populations can cause distorted, off-color foliage, reduce tree vigor and even kill limbs. They also produce honeydew which supports sooty mold. The sooty mold, when heavy, turns infested trees black and may interfere with photosynthesis. The honeydew attracts bees and ants – the latter often protect the aphids from predators such as lady beetles.

Life History and Habits - Aphid life cycles vary depending on species, host and weather. Many species lay eggs which overwinter in protected places on the trees. Others spend the winter as adults and reproduce throughout the year in warm areas. Overwintering eggs hatch in the spring, and emerging nymphs mature in a short time. Adults developing from overwintering eggs are usually all female and are commonly called "stem mothers" because they give rise to the summer generations. The "stem mothers" give birth to living young, without mating. Generally, the young are all females and they too give birth, without mating, to female living young. Reproduction commonly continues in this way (parthenogenetically) throughout the summer. Many species can go from birth to reproducing adult in as little as seven days with favorable weather, and populations can increase rapidly. Females of the summer generations may or may not be winged. Winged forms are produced at various times during the season, probably as a response to overcrowding, and winged females fly to other trees to start new colonies. At some point in the succession of generations, usually in the late summer or fall, most species produce males for a sexual generation. The males mate with females, which then lay overwintering eggs.

Control - Aphids are easily killed by labeled insecticides when infestations are discovered, although getting good coverage in the interior of older trees often presents problems. Reduce sooty mold accumulation by adding a small amount of dish-washer detergent to the sprays. The detergent makes the sooty mold more easily washed off by rains once the aphids are controlled. A clean-up insecticide application is normally suggested for marketable trees about two weeks before harvest begins.

Mites

Mites are not true insects since adult mites have eight legs. However, several kinds of mites attack conifers. Among the most common are the spider mite (Acarina:Tetranychidae). The genus Oligonychus

contains several damaging species, including the spruce spider mite, O. ununguis (Jacob).

Description - Mites may be green, yellowish, orangish or reddish. All are tiny, usually less than 1 mm long. Many are not visible without magnification. Adults have eight legs while larvae have only six.

Damage - Mites feed on foliage, destroying chlorophyll-bearing cells. Affected areas appear stippled, flecked or bleached. Heavily infested foliage may turn brown and drop.


Spruce spider mite adults.
Spruce spider mite adults.
Some spin light, delicate webs over their feeding sites, but webbing may or may not be evident, depending on species and population density.

Life History and Habits - Mites normally overwinter as eggs on needles or twigs of host trees. They emerge in early spring and begin new populations. The life cycle of spider mites typically includes the egg stage, a larval stage, 3 nymphal stages and the adult. The reproductive rate is rapid under favorable conditions. Some species go from oviposition (egg laying) to adult in as little as seven days. Damaging population levels can build up fast. Moderately hot, dry weather favors mite build-ups. Cool, rainy weather or extreme heat tend to reduce activity.

Control - Dormant oil sprays for scale insects often reduce overwintering mite populations. Foliar sprays with labeled miticides can be applied when mites and damage appear during the summer. Two or more miticide applications, seven to ten days apart, are usually required to achieve control. Most miticides do not kill the eggs and repeat applications are necessary to kill emerging mites.

Pine Spittlebug

The pine spittle bug, Aphrophora parallela (Say), occurs throughout most of the eastern states. Its favorite host appears to be Scotch pine, but it also attacks Virginia pine and a variety of other pines. It attacks trees of all sizes and ages.

Description - Adults are tan to dark reddish-brown, blunt, wedge-shaped insects somewhat resembling leafhoppers. They have two narrow, light bands, usually bordered by darker bands, on each wing cover and are 8 - 11 mm long. The wingless nymphs are usually found in frothy "spittle" masses (Fig. 15) and have a dark brown to black head and thorax with a cream-colored abdomen (Fig. 16).

Figure 15. Spittle Mass of Pine Spittlebug.
Figure 15. Spittle Mass of Pine Spittlebug.
  Figure 16. Pine spittlebug nymph. Showing the immature nymphal stage of the spittlebug feeding on pine and engulfed in its frothy 'spittle.'
Figure 16. Pine spittlebug nymph.
Showing the immature nymphal
stage of the spittlebug feeding on
pine and engulfed in its frothy "spittle."

Damage - Spittlebugs feed bu sucking plant sap. Heavy infestations can cause yellowing and stunting of new growth. Dieback of plant tips rarely occurs.

Life History and Habits - Spittlebugs usually spend the winter as eggs laid in dead woody tissue or just under the bark of twigs in July and August. Overwintering eggs hatch in the spring (April or May), and the young nymphs feed on twigs. While feeding, nymphs produce a droplet of clear fluid which surrounds their bodies, bubbles of air are incorporated into the fluid, giving rise to the characteristic spittle mass. The size of the spittle mass depends upon the size and number of nymphs congregating at the same feeding site. Nymphs move often and form new spittle masses at each stop. Older nymphs migrate to the trunk where there may be many in a single mass. When full grown, they move back to the needles and transform into adults, which are usually numerous in July and August. They feed without producing spittle masses. There is normally only one generation per year.

Control - Spittlebugs are often controlled by applications for tip moths or other pests. Spittle masses are striking and obvious. The insects can be controlled with various insecticides when masses appear.

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Last updated on Thursday, December 03, 2015 at 09:43 AM
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