Cottony-Cushion Scale (redirected from Icerya purchasi)

cottony-cushion scale

Cottony-cushion scales (Icerya purchasi, magnified)

(credit: Robert C. Hermes—The National Audubon Society Collection/Photo Researchers)

Scale insect (Icerya purchasi, order Homoptera) that is a pest especially of California citrus trees. The adult lays bright red eggs in a distinctive large white mass that juts out from a twig. Distributed worldwide, cottony-cushion scale is found on many other plants, including acacia, pittosporum, and willow. Australian ladybird beetles (see ladybug), a natural enemy, have been imported to keep it from destroying the California citrus industry.

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Cottony-Cushion Scale 

(Icerya purchasi), an insect of the family of giant coccids of the suborder Coccidae of the order Homoptera, a dangerous pest of citrus crops. The reddish brown body, which measures 5– mm long, is oval or nearly round. In mature females there is a large (sometimes 25 mm long), white, fluted ovisac. The cottony-cushion scale is native to Australia. As a result of the exportation of seedlings, the insect appeared in all countries in which citruses are cultivated. In the USSR it is found in the Abkhazian ASSR, the Adzhar ASSR, and Krasnodar Krai. The insect harms citrus crops, silver acacia, fig, pomegranate, cypress, and several other plants. There are two or three parthenogenetic generations each year. The larvae winter, and adult females appear in early May. The females soon deposit more than 2, 000 eggs in the ovisac. The larvae hatch in the ovisac and emerge within a few hours. Cottony-cushion scales sometimes congregate in large colonies on shoots, branches, trunks, leaves, and fruits. They suck out the juices of the plant. As a result, plant growth is inhibited and fruit yield is decreased.

The most widely applied control measure is the use of the predatory Australian lady beetle (Rodolia cardinalis), an example of a biological control measure for plant protection. When there is a large population of cottony-cushion scale, insecticides are used (a chemical control measure).

REFERENCES

Borkhsenius, N. S. Chervetsy i shchitovki SSSR. Moscow-Leningrad, 1950.
Rubtsov, I. A. Vrediteli tsitrusovykh i ikh estestvennye vragi. Moscow-Leningrad, 1954.

P. I. MITROFANOV