BROWN SOFT SCALE

James R. Baker, Extension Entomologist, Emeritus

General Information

Living adult female brown soft scales are pale yellowish-green to yellowish brown, often mottled with brown spots. Older females are brown. The body is usually oval in outline, up to 3/16 inch in length and slightly convex in profile. The shape tends to vary according to position on the host plant. Males are rare, but resemble tiny wasps or flies.

Crawlers and young nymphs are yellow and almost flat in profile. Parasitized nymphs are dark brown to black and convex. Crawlers have well developed legs and antennae and are quite active until settling. Older nymphs are sessile.

Biology

Brown soft scale has been reported feeding on hundreds of different plants. It can survive on most greenhouse plants, but seems to prefer perennials to annuals. Ferns are a favored host.

Brown soft scale is a frequently encountered scale on plants indoors. Infestations of brown soft scale can become so heavy as to encrust the stems and petioles of their host plant. They also settle on leaves, usually along midribs and occasionally on the fruit. Large colonies remove large quantities of plant fluids and can cause wilting, but they seldom kill their host. Immatures and adults produce much honey dew that serves as a medium for the growth of sooty molds. These fungi inhibit photosynthesis and make infested plants unsightly. Obnoxious insects such as ants and wasps are also attracted to feed on the honeydew.

Females retain their eggs in the body until hatching. Brown soft scales are born as active crawlers but remain under the body of the female for a short time before emerging and selecting a feeding site to settle and complete their development. Females molt twice before reaching maturity. Males undergo four molts before emerging as winged adults, but are rarely seen. All stages are found throughout the year in warmer regions and in greenhouses. Brown soft scales can complete three to seven generations per year depending on temperature. It takes about 60 days to complete a generation.

Control

The following pesticide formulations should control brown soft scales if applied to infested plants thoroughly. A second application may be necessary. Wait about 10 days between applications. Never set an ornamental plant out in the sun to treat it. Pesticide injury may result. Keep treated plants in the shade or treat during the cooler parts of the day so the foliage will dry before the plant is exposed to direct sunlight.

* Suitable for home use.

Useful Links:
Key to Families of Scale Insects of Florida
Hawaii Note http://www.extento.hawaii.edu/kbase/crop/Type/c_hesper.htm

Recommendations for the use of chemicals are included in this publication as a convenience to the reader. The use of brand names and any mention or listing of commercial products or services in this publication does not imply endorsement by the North Carolina Cooperative Extension Service nor discrimination against similar products or services not mentioned. Individuals who use chemicals are responsible for ensuring that the intended use complies with current regulations and conforms to the product label. Be sure to obtain current information about usage and examine a current product label before applying any chemical. For assistance, contact an agent of the North Carolina Cooperative Extension Service in your county.

Other Resources

• Back to Insect Notes
• Horticulture Information Leaflets(HILs)
• Plant Disease Notes
• North Carolina Agricultural Chemicals Manual
• North Carolina Cooperative Extension Service

ENT/ort-32
August 1994 (Revised) April, 1998

Web page last reviewed January, 2011 by the webperson.