Armored scales

Armored scales get their name from the hard, waxy coating that covers their bodies.They are not as economically damaging in greenhouses as are other scale insects because armored scales infest limited types of plants, mainly trees and shrubs, and they don't produce honeydew.They can be important pests in conservatories.

Damage

The plant damage caused by armored scale feeding is similar to that caused by soft scales.They inject toxins while feeding on leaf tissue.The toxins kill cells around the feeding site, causing a yellow or brown halo. Heavy feeding results in premature leaf drop. However, since armored scales don't produce honeydew, sooty mold is not a problem.

Description and life cycle

Armored scales are soft-bodied insects that live beneath a hard cover made of wax and protein.They are smaller than soft scales, varying in size from V25-V32 inch (1-4 mm). Armored scales vary in shape from circular to elongated (elliptical or like an oyster shell), in texture from smooth to rough, and in color.The insect body beneath the covering is usually yellow or orange.The males'cov-erings tend to be smaller and more elongated than those of the females. Most females lay eggs beneath their scale, but certain species produce live young under the scale.The crawlers move to other plant parts and settle for the remainder of their lives. A waxy covering that incorporates the shed skin of the crawler and subsequent stages builds up around the immature insect. Unlike soft scales, the scale covering on armored scales is easily removed from the scale's body.The adult female, which is legless, remains under its covering. Up to six overlapping generations may be produced in a year, depending on the species and environmental conditions.

Monitoring

Visual inspection of plants is the best way to detect armored scales.They are generally smaller than soft scales, not raised and bumpy, and are more easily overlooked.You can find them on lower leaf surfaces and stems, often forming thick crusts. New plant shipments should be checked carefully.

Natural enemies

Of the many parasites and predators that are known to attack armored scales, only a few have been utilized in greenhouse biological control efforts.

Parasites

Many parasites attack armored scales, including various Aphytis species that have been used against several armored scales in the greenhouse.The two species mentioned are in the families Aphelinidae and Encyrtidae, respectively.

Aphytis melinus. This ectoparasitic wasp from India and Pakistan attacks certain species of armored scales, including especially California red scale, but also ivy scale, San Jose scale and oleander scale.The tiny yellow wasp lays its eggs on the soft body under the waxy scale of third-instar nymphs. After developing as a larva for 2-3 weeks, the adult parasite emerges through a round exit hole cut in the scale.The adults can live 3-4 weeks, with each female killing more than 30 scales.This wasp does best at temperatures of 76°-85°F and relative humidity of 40-50%.This wasp is produced commercially for control of California red scale in citrus groves, but has not been evaluated for use in greenhouses. Pesticide-resistant strains are available. Another species,Aphytis ling-nanensis, sold commercially in Israel and Australia for California red scale control, has not been evaluated in greenhouses.

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