Ground pearls are scale insects that are found below the soil surface feeding on the roots of grasses. The adult female is a pinkish, soft-bodied insect with well-developed legs and antennae; the front legs are especially well developed. Adult males are small, gnat-like insects and are only rarely found. Eggs are pinkish white and are laid in clusters enclosed in a white, waxy sac. Nymphs (the ground pearl stage) have a hard, globular, yellowish shell and range from 1/16 to 1/8 inch in diameter. The sucking mouthparts extend through the wall of the cyst and are inserted into grass roots.
Overwintering takes place in the ground pearl stage (nymphs). Females mature in late spring and emerge from their cysts. After a short period of mobility, they settle 2 to 3 inches below the soil surface and secrete a waxy coat. Each female deposits approximately 100 eggs (without mating) inside the waxy coat during the early summer. Nymphs hatch in mid-summer and infest small grass roots. They develop the familiar globular appearance soon after they begin feeding. There is usually one generation per year, but if conditions are not favorable for emergence, female nymphs may remain in the ground pearl stage for two or three years.
Ground pearls infest the roots of grasses. Bermudagrass, St. Augustinegrass, zoysiagrass, and Centipedegrass are the most common hosts.
Nymphs suck sap from underground plant parts. During summer dry spells, irregularly shaped patches of grass begin to turn yellow. The grass in these spots eventually turns brown and usually dies by fall. Cysts are present in larger numbers at the interface between damaged and healthy grass and may be found as deep as 10 inches in the soil.
Inspection & Control
Examine the soil around grass roots, especially in the edges of damaged areas. Look for round, yellowish cysts, which are the only stage commonly found during most of the year.
Insecticides have not been effective against ground pearls, partly because they reside several inches below the soil surface. Good cultural practices such as watering and fertilization may help turfgrasses recover from injury and tolerate feeding by ground pearls, but such beneficial effects may be only temporary.