Description: Adult juniper webworms are small, brown moths (5/8 inch long) with white wing margins. They are rarely noticed, because they fly only when disturbed. Female moths lay tiny white or pinkish eggs that darken with age.

The juniper webworm caterpillar is a small (3/4 inch long), whitish or light brown worm with noticeable reddish-brown stripes. The pupa is light to dark reddish brown and is about 1/4 inch long.

JUNIPER WEBWORM CATERPILLAR
Photo courtesy of Dr. Jim Baker, North Carolina State University

The leaf-mining by newly hatched larvae is inconsequential. Feeding by larger worms may seriously damage ornamental junipers. Large masses of dead needles appear, and the shrubs look unthrifty. Small shrubs may be completely webbed.

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 50 to 200 eggs singly in the axil of new needles. About 10 days later, tiny larvae hatch, puncture the leaf and feed as leafminers, causing the leaves to 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 formed around the infested leaf. As the worm grows, the web is expanded 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 2 weeks to continue the infestation. There is one generation per year.

Control.

When practical, webbed masses should be pruned and burned. Braconid and ichneumonid wasps parasitize the larvae and pupal stages of juniper webworms.

Consult the current North Carolina Agricultural Chemicals Manual for insecticide recommendations.

MATURE BAGWORM
Photo courtesy of Dr. Jim Baker, North Carolina State University

Description. Female bagworms are wingless, legless and grub-like (they never leave the bag). Males are small, brown, hairy moths with dark wings that clear with age. Eggs are spherical or oblong and about 0.8 millimeters by 1.0 millimeter. Eggs are found in the mother's bag inside her pupal exuviae. The bagworms are 2 to 52 millimeters long, depending on age. The head and forward parts are dark and sclerotized and the rest is paler and soft. The bags are made of white silk with bits of the host plant spun onto the outer surface. The pupae are dark brown. Male pupae are slender and female pupae are fatter. The pupal stage occurs inside the bag.

Biology. Bagworms occur throughout North Carolina. Bagworms have a very wide host range but are usually associated with arborvitae or juniper. A single bagworm does relatively little harm as it feeds on leaves. Excessive defoliation may kill conifers within one or two seasons. Damage is most noticeable in landscapes rather than woodlands. Occasionally, prior to pupation, the silk band with which the bagworms attach themselves to a twig will cause twig girdling as the twig grows.

The worms spend the winter as eggs (500 to 1000) in the mother's bag. They hatch in May and June. The newly hatched larvae spin down on silken threads and are blown about by the early spring breezes. Most of the larvae land on the original host plant but some small worms may be "ballooned" for some distance on the silk thread.

Upon reaching a suitable host, the worm begins to spin its bag. As the bagworm grows, it enlarges the bag by incorporating fresh plant foliage to the outside of the bag for camouflage. In August, the worms mature and molt into the pupal stage. The bag is firmly attached by a sturdy silk band wrapped around a twig.

Male moths emerge to mate during August and September. After mating, females lay their eggs inside the pupal exuviae and die. Newly hatched larvae often have difficulty adapting to plants different from their parents' host plant, and may die or may produce few offspring. After several years of struggle, the population may hit on the right combination of genes for the "new" plant and "suddenly" cover the new plant with bagworms.

Control. When practical, bagworms can be removed with scissors or a sharp knife. Bagworms are parasitized by several kinds of parasitic wasps. Insecticides are effective when applied in June or early July when the bagworms are small and relatively sensitive. The North Carolina Agricultural Chemicals Manual should be consulted for current recommendations.

SPRUCE SPIDER MITE DAMAGE
Photo courtesy of Dr. Jim Baker, North Carolina State University

Description. Spruce spider mites are cool weather mites. They are black in color and, with their legs extended, no larger than the period at the end of this sentence. Eggs are red or brown, round and a little flattened. They have a tiny hairlike "stripe" sticking up in the center. The eight-legged larvae are slightly larger than the eggs. Nymphs are similar to adults although some nymphs are smaller.

Biology. Spruce spider mites are found throughout North America feeding on junipers, spruce, arborvitae, and other coniferous evergreens.

Spider mites hatch from eggs and develop through larval and nymphal stages before maturing into adults. Males mate with females as soon as the females molt into the adult stage and females soon begin laying eggs. Mites overwinter as eggs usually laid at the base of needles.

In April and May the eggs hatch and larval mites begin feeding. Most feeding damage and reproduction takes place in spring and fall. At higher elevations, the spruce spider mite may be active all summer.

Control. Because these mites are active in cool weather, infestations should be treated at the end of winter or summer. Spruce spider mites tend to feed on older leaves. If pesticides are used, thorough coverage is essential for good control. The North Carolina Agricultural Chemicals Manual should be consulted for current recommendations.

JUNIPER SCALE ADULT
Photo courtesy of Dr. Jim Baker, North Carolina State University

Description. The juniper scale is a fairly damaging pest. Infested conifers often have dead or stunted twigs and uneven growth. The juniper scale insect is a very small (up to 1 mm) armored scale insect. The armor of females is circular to oval and is white and parchment-like. In the center is a light yellow cast skin of the earlier female nymph stages. The armor of the male scales is oblong, white and about 1 millimeter long. At one end is the pale yellow cast skin of the crawler stage. Adult males are tiny, gnatlike insects with four eyes and a tiny waxy tail filament.

Biology. Little is known of the biology of juniper scale insects. Other armored scales hatch from eggs laid by the mother under her armor. The tiny crawlers emerge to seek a suitable place to feed. Female scales molt twice before maturing and male scales molt three times. Males emerge from their armor and seek females with which to mate. Females soon lay eggs for another generation. Males die after mating; females after laying eggs.

The armor of both males and females clings to the infested shrubs long after the scales inside die (females) or leave (males). They are found on the needles and bark of Cedrus, juniper, cypress, spruce, and Leyland cypress. Because they are so small, juniper scales are easily overlooked. The juniper scale is a debilitating pest of junipers and is considered an economic pest.

Control. Horticultural oils should give adequate control of the juniper scale. Consult the current North Carolina Agricultural Chemicals Manual for control recommendations.

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