Brown Soft Scale

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DESCRIPTION

Adult-
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, 2.5 to 4 mm in length and slightly convex in profile. The shape tends to vary according to position on the host plant. Males look like tiny two-winged wasps or flies and are rare.

Other Stages-
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.

Fig. 123: Brown Soft Scale
Coccus hesperidium Linnaeus, Coccidae, HOMOPTERA
A, Mature female. B, Side view of female. C, Crawler. D, Infested spider plant.

BIOLOGY

Distribution-
Brown soft scale is cosmopolitan in tropical and subtropical regions and in greenhouses in northern regions. In North America it occurs out of doors in the deep South, and north along the eastern seaboard to Virginia and as far north as southern Vancouver island on the west coast.

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

Damage-
Brown soft scale is probably the most 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.

Life History-
Females are ovoviviparous and retain the 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

Brown soft scales are surprisingly difficult to control even though there is no external egg stage and only a few very young nymphs are protected by the body of the mother. Although reported as a pest species of many host plants in many countries, outdoors it may be suppressed by natural enemies in many areas. Scutellista cyanea Motschulsky is a common parasite and Metaphyous luteolus Timberlake controls brown soft scale in California. For specific chemical control recommendations, see current Cooperative Extension publications on ornamental plant pest management or consult your county Extension agent.