How to Effectively Eliminate Mealybugs from Your Austrian Pine Tree

Key to Conifer Pests

Included in this section are pests that infest arborvitae, cedar, deodar cedar, fir, hemlock, juniper, pine, and spruce in nurseries and in the landscape. Conifers form a major portion of the shrubs grown by commercial nurserymen. With their amazing variety of forms and shades of green and yellow, conifers are among the most important landscape plants. Although conifers generally require little care, they are occasionally damaged or killed by insects and spider mites in the landscape.

• Arborvitae leafminer – Arborvitae leaves are tunneled and brown; heavily infested shrubs are unthrifty and defoliate prematurely; tiny (1- to 3-mm), greenish or brownish caterpillars are found in tunnels.
• Bagworm – Spindle-shaped silk bags covered with pieces of plant foliage hang from twigs; when bagworms are numerous, much of the plant may be defoliated and may die.
• Balsam twig aphid – Needles of Fraser fir twisted and curled; bark may have a roughened appearance; aphids are bluish gray but are present only very early in the growing season.
• Balsam woolly adelgid – Gouty and twisted new growth of fir; needles defoliating prematurely; small, cottony fluffs on the bark of trunk and branches with small, bluish-black insects underneath; heavily infested trees declining or dead.
• Eastern spruce gall adelgid – Pineapple-shaped galls at the base of new twigs; growth distorted at older galls; small, greenish-white aphids in new galls.
• Introduced pine sawfly – Colonies of grayish caterpillars with rows of black and yellow spots on sides feed on white and Virginia pines. Heavily infested trees may be defoliated.
• Juniper webworm – Foliage of junipers webbed together by silk strands; heavily infested shrubs with much dead foliage incorporated in the webbing and dead foliage below the shrub; slender, whitish worms with brown stripes in webbing.
• Nantucket pine tip moth – Dead buds and shoots are hollowed out; small worms or pupae are inside. Small (up to 6-mm), gray moths may be noticed around dusk.
• Pine bark adelgid – Small (up to 3-mm), dark insects with conspicuous white, waxy filaments feeding on back. Most noticeable in late winter and spring.
• Pine needle scale – Needles of pine (sometimes balsam fir, Cedrus, Juniperus) infested with small (1 to 4-mm), white scale insects with light-yellow exuviae on one end.
• Redheaded pine sawfly – Colonies of yellowish caterpillars with brown spots and orange heads feeding on foliage; small shrubs may be completely defoliated.
• Spittlebugs – Masses of frothy liquid on twigs of pine. Twig dieback common.
• Spruce spider mite – Foliage pale yellowish or whitish; foliage may drop prematurely; spider mites may be present in large numbers; foliage may be webbed with fine silk webbing.
• White pine aphid – Large (up to 6-mm), dark, soft-bodied insects sucking sap from twigs and branches of white pine. Honeydew and sooty molds often present.

Arborvitae leafminer, Argyresthia thuiella (Packard), Yponomeutidae, LEPIDOPTERA

DESCRIPTION

Adult – The adult is a small (about 6-mm-long), light gray (with brown and black spots) moth with a wingspread of about 8 mm. The antennae are long and slender. The legs and abdomen are light brown (Figure A).

Egg – The egg is tiny (0.4 mm by 0.25 mm) and almond shaped with wrinkled sculpturing on one end. It is pinkish but turns darker as the embryo matures.

Larva – The larva is a small (0.75- to 3-mm), green (sometimes with a reddish tinge) or brownish caterpillar with a black head and cervical shield.

Pupa – The 3.5- to 4-mm-long pupa is greenish but turns brownish red as it matures. The tail segment has a group of six to eight short, stout hooks (the cremaster).

BIOLOGY

Distribution – The arborvitae leafminer is known from New England and eastern Canada south to the Middle Atlantic states and west to Missouri.

Host Plants – The arborvitae leafminer apparently confines its feeding to all varieties of arborvitae but seems to prefer American pyramidal, globe, and golden arborvitae (about in that order).

Damage – Mined leaves detract from the appearance of infested arborvitae (Figure A). Heavily damaged leaves may drop from the plant prematurely, and in extreme cases the plant may be killed.

Life History – Arborvitae leafminers overwinter as larvae in the mined leaves. Pupation occurs and adults appear in late spring and throughout the summer. After 2 or 3 days, females deposit eggs in the axils of branchlets or along leaf margins. A female may oviposit for 4 or 5 weeks. Most of the eggs are laid around the first of June. Newly hatched larvae bore into the leaves and feed for the rest of the season. The larvae mine from the tips of branchlets toward the bases and allow the frass to collect in the tunnels until winter. When mining is resumed the following spring, the frass is expelled from the mine. Larvae will sometimes leave old mines and begin new ones. Pupation occurs in the new portion of the mine after an exit hole has been chewed and takes place from March to May. The pupal stadium is 3 to 5 weeks. Pupae face the exit hole.

CONTROL

Some control may be obtained by pruning out infested tips in the fall. Hymenopterous parasites also help control the population. If a spray is used, it should be applied in early June or late May. For specific chemical controls, see the current state extension recommendations.

Bagworm, Thyrirlopteryx ephemeraeformis (Haworth), Psychidae, LEPIDOPTERA

DESCRIPTION

Adult – The female is wingless and grublike with tiny, useless legs. The male is a small, brown, hairy moth with clear wings.

Egg – The yellow egg is slightly oblong or spherical, about 0.8 mm by 1.0 mm. It is found in the mothers bag, usually in her pupal exuviae.

Larva – The male is 2 to 43 mm long; the female, 2 to 52 mm. The head and forward parts are dark and sclerotized the remainder is pale amber. Larval bags grow to about 5 cm long and 12 mm wide (Figure G).

Pupa – The pupa is dark brown. Males are slender posteriorly, and females are cylindrical. The pupal stage is spent inside the bag.

BIOLOGY

Distribution – Bagworms occur throughout the eastern United States.

Host Plants – Bagworms feed on many trees including maple, boxelder, sycamore, willow, black locust, elm, linden, poplar, oak, apple, wild cherry, sassafras, and persimmon; but the preferred hosts are conifers. Arborvitae is highly susceptible.

Damage – A single bagworm does relatively little damage. Yet because females do not fly, populations are often very dense; and excessive defoliation may actually kill conifers within one or two seasons. Damage is most noticeable on ornamental plantings rather than in forests and woodlands.

Life History – The bagworm is sometimes called the evergreen bagworm. Populations vary, but occasionally bagworms become extremely abundant, alarming homeowners. The winter is spent as eggs (500 to 1,000) in the mothers bag. They hatch in May and June, and the young worms drop from the bag on a slender silk thread. Such small worms may be “ballooned” for short distances on this long thread. In August, the worms mature and change into the pupal stage. During August and September, male moths emerge from their bags to mate, living 1 or 2 days. Female bagworms, living 4 to 9 days, do not leave the bag until the eggs are laid. Before the young worm feeds, it secretes silk and forms a bag. Bits of plant tissue become enmeshed in this bag when the worm feeds. As the worm grows, the bag enlarges, reaching about 5 cm when complete. It is fastened to the plant by silk manufactured whenever the worm rests or molts.

CONTROL

Where practical, bagworms can be removed with scissors or a sharp knife. Bagworms are parasitized by several ichneumonid and chalcid wasps. Low winter temperatures and bird predation on small larvae are also limiting factors. Chemical control is effective, particularly in June and early July when the bags are small. For specific chemical controls, see the current state extension recommendations.

Balsam twig aphid, Mindarus abietinus Koch, Aphididae, HEMIPTERA

DESCRIPTION

Adult – Stem mothers (fundatrices) are wingless, bluish gray aphids. Sexuparae and egg-laying adults (sexuales) have wings, five dark spots on the thorax, and four sclerites on the top of the abdomen. The honey tubes are indistinct.

Egg – The brown eggs are covered with small, white rods of wax. They are laid in crevices in the bark.

Nymph – The nymphs are small, pale yellowish-green, wingless aphids. Nymphs that develop into egg-laying adults are slender.

BIOLOGY

Distribution – Balsam twig aphids have been found from Maine to Washington and in both the Rocky Mountain and Appalachian Mountain regions. They apparently occur wherever balsam fir, white fir, and spruce are grown.

Host Plants – This aphid feeds on a wide variety of hosts, including balsam, Siberian, alpine, and Fraser firs; white spruce; and juniper.

Damage – Balsam twig aphids cause curled needles and roughened bark of infested Fraser firs (Figure H). Although trees may tolerate large populations, eventually they will decline in vigor. Most serious damage occurs in Christmas tree plantations, where appearance and market value of infested trees are degraded and reduced.

Life History – Balsam twig aphids are unique pests because of their confusing life cycle and short feeding time. Each generation is different from its parent generation, and only one generation each year lays eggs. Most of the year is spent in the egg stage in crevices of the bark. The eggs are laid in early summer, and they remain on the tree throughout the fall and winter. In early spring the eggs hatch and the first generation of nymphs develops into wingless aphids called stem mothers (fundatrices). The stem mothers give birth to live nymphs, which may develop into wingless forms called fundagenae or winged forms called sexuparae. The egg-laying adults (sexuales) are winged and are the offspring of either the fundagenae or sexuparae. All of this happens in the spring and early sum mer. By the end of June, the eggs have been laid and the adult aphids have disappeared.

CONTROL

Control of balsam twig aphids is difficult because the damage occurs in early spring when weather is unpredictable. For specific chemical controls, see the current state extension recommendations.

Balsam woolly adelgid, Adelges piceae (Ratzeburg), Phylloxeridae, HEMIPTERA

DESCRIPTION

Adult – The balsam woolly adelgid is a small (about 1mm), round, bluish-black or purple sucking insect covered by woolly strands of wax (Figure I). The mouthparts are long (1.5 mm) and slender. (They may break off when the insect is removed from the host.)

Egg – The ovoid, amber egg is usually found in a mass of waxy strands and eggs.

Nymph – The newly hatched nymph is called a crawler. It is a small (0.35-mm), amber, flattened insect with red eyes. As it matures, the older nymph generally resembles the adult except for size. The overwintering form (neosistens) of the crawler flattens itself to the bark and secretes a waxy fringe at the body margin.

BIOLOGY

Distribution – Apparently limited in its northern distribution by cold weather, balsam woolly adelgids infest firs in southern Canada, the Pacific Northwest, and the northeastern United States. They also occur in the Appalachian Mountains as far south as North Carolina. They are distributed by wind in the crawler stage. Birds and other animals can also spread this pest. However, adelgids probably reached North Carolina on infested nursery stock.

Host Plants – Balsam and Fraser firs are the host plants for balsam woolly adelgids in the eastern United States. Apparently all species of firs (Abies spp.) are infested by this pest. However, while some species are very tolerant (Noble fir), other species are devastated by the pest (balsam, Fraser, and sub-alpine firs)..

Damage – Balsam woolly adelgids, introduced from Europe or Asia, were first noticed in Maine in 1908. Billions of feet of fir timber have been killed by balsam woolly adelgids in North America. Balsam woolly adelgids secrete an irritating salivary substance, which is injected into the host as they feed. This substance causes unusual growth (swelling or “gouting”), which distorts the normal growth pattern. Branchlets thicken, twist, and bend down at the ends. The main stem tapers rapidly at the top, and the tip bends or becomes flattened. A heavy stem attack may kill an otherwise healthy tree in 3 or 4 years. The wood of heavily infested trees becomes brittle and darkened.

Life History – Balsam woolly adelgids overwinter as first-stage nymphs. In spring, development resumes and the insects mature about the time the buds begin to break (mid-April). Eggs are deposited in spring and summer. Each egg is attached to the bark behind its mother by a waxy thread. In warm weather the eggs hatch in a few days. Up to 248 eggs are produced by each female. By fall all stages may be present. Three generations occur each year in North Carolina. Balsam woolly adelgids feed anywhere on the tree from which they can reach the parenchyma of the cortex (living portion of the bark) with their mouthparts.

CONTROL

Low winter temperatures and a small, brown beetle, Laricobius erichsonii, are important natural agents of control. Silvicultural methods (clean cutting, prompt salvage in winter, short rotation, etc.) will lessen the effect of the pest. For specific chemical controls, see the current state extension recommendations.

Eastern Spruce Gall Adelgid

Eastern spruce gall adelgid, Adelges abietis (Linnaeus), Phylloxeridae, HEMIPTERA

DESCRIPTION

Adult – A close relative of aphids, the adult eastern spruce gall adelgid is a small, bluish-green sucking insect, covered by cottony, waxy strands. The summer generation develops wings.

Egg – The black, oval egg is laid in a cottony mass of waxy strands.

Nymph – The yellowish- to bluish-green nymph grows to a length of about 1 mm. An exposed nymph is usually covered by cottony, waxy strands, which may obscure the nymph.

BIOLOGY

Distribution – The eastern spruce gall adelgid was introduced apparently from Europe before 1900. Since then it has spread throughout the northeastern United States and southern Canada, south at least to North Carolina.

Host Plants – Norway and white spruce are the favored hosts of the eastern spruce gall adelgid, but it has been found on red, black, Engelmann, and Colorado blue spruce as well.

Damage – The eastern spruce gall adelgid causes minor physiological damage to its host plants unless the host is severely infested. Severely infested trees may decline in vigor. The primary damage is that of reduced aesthetic value of host plants in nurseries, Christmas tree plantings, or landscapes. The galls are 1.5 to 2 cm long and pineapple shaped. In summer the galls dry out and turn brown. The stem is often distorted at the gall.

Life History – Eastern spruce gall adelgids overwinter as partially grown females (stem mothers) near or at the dormant buds. In early spring the stem mothers mature and lay 100 to 200 eggs surrounded by cottony or woolly wax. The eggs are laid about the time the buds break. About 10 to 14 days later, the nymphs hatch and begin to feed at the bases of the needles. Their feeding causes a pineapple-shaped gall to form in the new twig. The nymphs mature in cells inside the gall until the gall dries out and splits open in summer. Although winged, the females usually stay on the host and soon lay up to 60 eggs in a cottony or woolly wax, usually at the tips of needles. The nymphs from this summer generation of eggs are the overwintering forms. There is one generation per year, and there are no males.

CONTROL

The overwintering nymphs should be controlled in early spring before new growth begins. For specific chemical controls, see the current state extension recommendations.

Introduced pine sawfly, Diprion similis (Hartig), Diprionidae, HYMENOPTERA

DESCRIPTION

Adult – Like a fly in appearance, the introduced pine sawfly differs from a fly in that it has two pairs of wings. The female sawfly is black and yellow with threadlike antennae and averages 8 mm long. The male sawfly is brown and black with broad, feathery antennae and averages 7 mm long.

Egg – When first laid, the egg is pale bluish white and about 1.5 mm long. It has straight sides and blunt, rounded ends. Before hatching, the egg becomes slightly enlarged and turns dark green

Larva – Less than 3 mm long when newly hatched, the young larva is dull gray with black legs. The larva undergoes subtle color changes as it matures and eventually becomes dark gray or black with white and yellow spots, a shiny black head, and a dark, double stripe down its back. A fully grown larva may be as long as 25 mm.

Cocoon – The pupa is enclosed within a dark-brown cocoon 7 to 9 mm long and 3.5 to 4 mm wide. The cocoon of a female sawfly is slightly larger than that of a male sawfly.

BIOLOGY

Distribution – The introduced pine sawfly occurs from Maine, Ontario, and Quebec into the North Carolina mountains and westward through the Central and Great Lakes states into Minnesota. Only recently a problem in North Carolina, this pest has been reported from the Mountains eastward to the Piedmont.

Host Plants – Five-needled pines and soft, two-needled pines are the preferred hosts of this pest. White pine is particularly subject to infestation; Scotch, red, jack, and Austrian pines are also commonly injured.

Damage – Sawfly larvae damage conifers by defoliation. Ragged, shredded edges on the outer tips of needles are the first sign of infestation. Young larvae are responsible for this type of injury. Older larvae consume entire needles and nibble at the bark. If heavy defoliation occurs late in the season after bud formation, branches or entire trees may be killed. Those trees or shrubs that survive infestation often lose much of their top growth.

Life History – Studies of the biology of the introduced pine sawfly in the southern Appalachians are just beginning. Therefore, little is known concerning its life history in North Carolina. The following information is based on life history studies in the more established areas of its range.

Introduced pine sawflies overwinter as prepupae inside cocoons usually hidden among ground litter. First generation adults appear from April to June, the first eggs being laid around mid-May. Depositing an average of 70 eggs, females insert about 10 eggs in a row into single pine needles. Ten to 14 days later, larvae hatch from the eggs and feed on conifers. In late July, larvae begin spinning cocoons among needles, in bark crevices, or at the base of small branches.

Second-generation sawflies first appear in early August. Seven or 8 days after eggs are laid, larvae hatch and feed until September. Cocoons are then spun on trees or among soil litter. Some of these cocoons overwinter, but adult sawflies emerge from others and produce a partial third generation in late fall. However, most of these late larvae, as well as prepupae in cocoons on trees, are killed by low winter temperatures. Cocoons among soil litter have the best chance of surviving the winter.

CONTROL

Parasites, predators, and low winter temperatures kill well over half of the overwintering sawfly population; yet heavy infestation inevitably recur. The treatment of large areas of trees is not practical, but small, localized infestations can be controlled. Pesticides are available for applications to infested yard trees, shrubs, or nursery stock. Since generations overlap and all life stages may be present at once, repeated pesticide applications may be necessary to control new sawfly larvae as the emerge. For specific chemical controls, see the current state extension recommendations.

Juniper webworm, Dichomeris marginella (Fabricius), Gelechiidae, LEPIDOPTERA

DESCRIPTION

Adult – The juniper webworm is a small, brown moth (6 to 7 mm) with white wing margins. It is rarely noticed when flying unless it is disturbed.

Egg – The whitish, pinkish, or dark reddish-orange egg is 0.5 mm by 0.3 mm. It is subcylindrical with rounded ends. The surface has many longitudinal, waxy lines.

Larva – The larva is a small, whitish to light-brown worm (0.5 to 15 mm) with reddish-brown stripes (Figure Y).

Pupa – The light or dark reddish-brown pupa is almost as long as the adult (5.5 mm).

BIOLOGY

Distribution – The juniper webworm was first reported on juniper in Europe in 1775. It also occurs in northern Asia except Siberia, the eastern and midwestern United States, California, Oregon, and Idaho. Southern areas of Canada adjacent to infested areas in the United States are infested as well.

Host Plants – Irish juniper is the preferred host, although Chinese juniper, red cedar, and Juniperus communis varieties aurea, horizontalis, depressa, hibernica, suecia, and squamata meyeri are also infested. Juniperus procumbens and J. squamata are infested only occasionally.

Damage – The leaf-mining by newly hatched larvae is inconsequential. The feeding of larger worms in the fall and following spring may seriously damage ornamental junipers. Large masses of dead needles appear, and the shrubs look unthrifty. Small shrubs may be completely webbed (Figure Y).

Life History – Juniper webworms overwinter as partially to nearly grown worms inside webbed masses of foliage. Adult emergence occurs from May to July, peaking in June. Males live about 12 days; females, about 14. After mating, females lay from 50 to 200 eggs singly at the base of new needles in the axil. About 10 days later, tiny larvae hatch, puncture the leaf surface, and feed as leafminers, causing the leaves to turn brown. The mined leaf is used as a protective retreat from which the tiny worm emerges to feed on fresh foliage. A tiny, white web is soon formed around the infested leaf. As the worm grows, the web expands to encompass dead leaves. Silken tubes are then constructed in which the worms retreat when not feeding. The worms mature throughout the summer, fall, and winter. By the following spring, they feed gregariously and form a community web. Considerable amounts of foliage may be spun together, and small trees may be completely webbed. The worms pupate inside whitish silken cases, and new adults appear in about 14 days to continue the infestation. There is one generation per year. Braconid and ichneumonid wasps parasitize the larval and pupal stages of juniper webworms.

CONTROL

Where practical, the webbed masses should be pruned and burned. For specific chemical controls, see the current state extension recommendations.

How to Get Rid of Mealybugs – Part 1 of Logee’s “Pest Prevention” Series

FAQ

What is the fastest way to get rid of mealybugs?

What is the best killer for mealybugs?

Can I spray vinegar on mealybugs?

How do I get rid of mealy bugs on my plants?

If you see mealy bugs on your plants, there are several control options: Wash them away. Mealy bugs can be dislodged with a steady stream of water. Repeat the treatment as necessary. This is best for light infestations. Neem oil for outdoor plants. Neem oil is an organic oil derived from the neem tree. Use according to label instructions.

What plants are affected by mealybugs?

Some of the most common plants that are affected by mealybugs include: Citrus trees: Mealybugs are a common pest of citrus trees and can cause damage to the leaves and fruit. Houseplants: Many types of houseplants, including tropical plants like pothos and philodendron, are susceptible to infestations.

Are mealybugs hard to get rid of?

A light mealybug infestation is easy to get rid of, but heavy infestations can be more difficult. Light infestation: Light mealybug infestations are when you detect a few mealybugs and their white, cottony egg masses on the plant.

How do you get rid of mealybugs?

Adult mealybugs’ waxy coating is like armor that is difficult to penetrate, but there are a couple of systemic chemical insecticides that can be effective against mealybugs: Dinotefuran for landscape plants, and imidacloprid for houseplants. These have to be applied to the soil and taken up by the plant.