The juniper scale, Carulaspic juniperi (Fig. 1), is a sporadic pest of juniper, cypress, and cedar trees in nurseries and landscapes in Georgia. Native to Europe, the juniper scale is now widespread in the eastern US. It is an armored scale where the wax cover is not a part of the insect body but rather can be separated from the insect body. Juniper scale feeds on plant fluid with their piercing sucking mouthparts, after it settles on the needles of conifers. In heavy infestations, plant vigor can be reduced, causing needle drop and twig color change from green to brown, making the plants unhealthy.
Description and biology
The wax covers of the female scale are circular, white, and about 1/16 inch in diameter (Fig. 2). The immature males are smaller, white, and elongated (Fig. 2). The shed skin from the scale body is incorporated into the cover, and it appears yellow-colored. Adult females overwinter on the needles. In the spring, females produce approximately 40 eggs that hatch within two weeks; yellow crawlers are present in late spring. The crawlers are tiny, approximately 2 mm long dark red in color. They are noticeable with naked eyes. The crawlers are dispersed by wind or birds to neighboring trees, where they settle by inserting their hair-like mouthparts into the plant, and molt into immobile nymphs. The female scales have three nymphal stages, whereas males have five. The winged adult males lack mouthparts and die immediately after mating. They undergo one generation per year.
Damage
Juniper scales colonize the needles of the hosts. The adults and nymphs of scales cause the damage. The affected plants lose vigor and rarely produce new growth. The new growth, if present, will not be evenly distributed, and the tree appears stunted. Yellowing and dieback of needles are common symptoms and are clearly evident after infestation (Figs. 3 and 4). Similar to other armored scales, the juniper scale does not produce honeydew.
Host range
The juniper scale attacks various junipers, such as pfitzer juniper, Irish juniper, savin juniper, and Chinese juniper. It occasionally becomes a problem in landscapes and nurseries. They can infest and survive on Leyland cypress, false cypress, arborvitae, cryptomeria, incense cedar, and eastern red cedar.
Management
Insects generally thrive on stressed plants, and the juniper scale is no different. In nurseries, scales can easily find many hosts, often of the same species. Proper irrigation along with timely and adequate fertilizer applications may reduce tree stress. As part of cultural management, the densities of scales can be reduced by pruning severely infested twigs. The pruned twigs can be collected in sealed plastic trash bags and left in direct sunlight. The heat generated inside the bag will kill the scales. A few tiny parasitic wasps and ladybugs were reported from the juniper scale, but the impact of these biological control agents has not been studied thoroughly.
The application of dormant oil spray in the winter can cause substantial mortality of overwintering adults. Contact insecticides, such as horticultural oil or insecticidal soap are effective if used for the crawler stage of the juniper scale. The crawlers are produced during the late spring (May). Still, it is critical to accurately determine the initial crawler activity to time the application of contact insecticides for effective management. Double-sided sticky tape or electric tape with the sticky side facing out can be used to monitor crawler emergence. The crawlers will be caught on the edge of the tape, indicating crawler emergence. Sticky tapes should be visually observed at regular intervals (at least weekly). The horticultural oil or insecticidal soap concentration should be about 1% because some species and cultivars of juniper are sensitive to higher concentrations causing phytotoxicity. The residues of horticultural oil and soap will break down quickly in the environment and are considered an organic management approach. Crawlers can also be controlled with more persistent contact insecticides, but contact insecticide application on adult female juniper scales is ineffective because they are protected from the thick waxy cover.
Systemic insecticides, such as dinotefuran, can be used in the fall and spring as a soil drench or granular application when a severe infestation occurs. If a systemic insecticide is chosen, the application of contact insecticide can be avoided. Contact your local Extension office for the most up-to-date control recommendations. Please carefully read the insecticide label because the label is the law. After application, the tree’s health should improve with new growth vigorously appearing with standard color.
