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Adult- Depending on the host plant, the adult scale may vary in size. The scale varies from 4.5 mm on Cycas to as small as 2.0 mm on Asparagus fern. Relatively hemispherical, brown, smooth, and shiny, the scale may resemble a miniature army helmet. Young females may have a pattern of ridges in the form of the letter "H" on the dorsal surface.
Egg- The oblong, pinkish beige eggs are about 0.7 mm long and are protected by the mother's body in a mass of hundreds
Crawler- The flat, pinkish beige crawler is about 1.0 mm long with two red eye spots. The antennae and legs are short and spindly. There are two setae protruding from the rear.
Nymph- Nymphs are semitransparent, light yellow or fig! pink, and flat (young) to humped (older). They are so closely attached to the host plant that the legs and antennae are concealed. Two pale lines start at the margin on each side and fade in intensity toward the middle. Nymphs and young adults may exhibit the characteristic "H" pattern of the black scale group.
Distribution- From its probable origin in South America, the hemispherical scale insect is now found in greenhouses and interiorscapes throughout the United States.
Host Plants- The hemispherical scale insect has a wide range of hosts including bamboo, camellia, chrysanthemum, crape myrtle, croton, ferns, figs, gardenia, honeysuckle, lily, orchids, and zamia.
Damage- The secretion of honeydew and subsequent formation of sooty mold detracts from the beauty and commercial value of the plant. Feeding causes the plant to become stunted and lose its leaves.
Life History- The hemispherical scale insect is a tropical insect that has become a common greenhouse pest. In warmer temperate areas, the scale can live outside. Unlike many other scales, the hemispherical scale secretes little wax. However, the scales do produce much honeydew which allows sooty mold to grow. Males are unknown and reproduction is by parthenogenesis. Each female may deposit up to 1000 eggs. d After laying the eggs, the female dies and her body shrinks to form a cup or helmet over the eggs. Development for the egg stage and the three nymphal instars requires at least 40 days and may take as long as 105 days. There may be several generations each year in the greenhouse, with all stages being present at any one time. The nymphs do not move much once they have begun to feed. The hemispherical scale insect has a low rate of parasitism indoors, and it often becomes a serious pest.
Hemispherical scale insects are relatively difficult to control because the eggs and young nymphs are protected by the body of the mother. For specific chemical control recommendations, see the current Cooperative Extension publications on ornamental plant pest management or consult your county Extension agent. The most important parasite of hemispherical scale in the United States is Metaphycus helvolus Compere.
University of Florida/IFAS Reference to Pest Control Guides