What is killing my lawn? That is the million-dollar question, and the one most frequently asked since lawns have greened up. I’m sad to report that the most common diagnosis I have made with dead or dying lawns has been the dreaded ground pearl. Ground pearls, also known as pearls, pearl bugs, earth pearls, pearl scale, and a host of other names I’d rather not have printed, are scale insects that infest and damage lawns across Sampson County and North Carolina. They attack the roots of Bermuda, St. Augustine, Zoysia, and quickly decimate Centipedegrass.
Ground pearl nymphs extract juices from underground plant parts which cause circular dead areas that resemble fairy ring. The damage is most apparent during dry spells in summer. Most homeowners first notice irregular patches of grass which quickly turns yellow, and dies by fall. The spots enlarge each year and only weeds grow in the infested areas. Overwintering takes place in the pearl stage. Females usually mature in late spring and emerge from their cysts.
After a brief period of mobility, females tunnel 2 to 3 inches into soil and secrete a waxy coat. Within this protective covering, females develop eggs (without mating) and deposit them throughout early summer. Approximately 100 eggs are laid by each female. The slender nymphs emerge in mid-summer and infest grass rootlets. Once they initiate feeding, nymphs soon develop the familiar globular appearance. There is usually one generation each year. However, if conditions are not favorable for emergence, female nymphs may remain in the pearl stage for several years. Ground pearls are circular in shape, colored from pearly white to light tan, and look similar to slow release fertilizer pellets.
An easy way for homeowners to check for ground pearls is to dig a six inch square of sod three to four inches deep in the transition area between living grass and dead grass. Carefully sift through the soil with your hands and look for these pearl-like insects. Some may not fall out in the soil and can still be attached to the roots, so look closely at the root structure. If you fail to find any, try several more places as ground pearls occur in clusters.
Currently there is no treatment for ground pearls, and the best recommendation is to maintain a healthy and vigorous growing lawn to compensate for the ground pearl damage. Take routine soil samples and follow fertilization and liming recommendations accordingly. Since ground pearls only affect turf, you can also redesign your landscape and install flower beds, shrubbery or plant trees in infested areas.
On a positive note, some species of grass can tolerate ground pearl damage better than others. In trials conducted by North Carolina State University (NCSU), “El Toro” zoysia tolerated ground pearl damage better than other species in the study. Other vigorous turf grasses like “Celebration” Bermuda and varieties Bahiagrass also did well when managed under best management practices.
According to Dr. Rick Brandenburg, Professor and Extension Turfgrass Entomologist at NCSU, some success has been achieved with the use of a mixture of imidacloprid (Merit), a horticultural oil, and wetting agent applied twice a year when the pearls are in nymph stage. NCSU has conducted trials in previous years and although they were not able to document a reduction in ground pearls, they did see an increase in turf quality in bermudagrass. This suggests that in the future some combination of treatments may prove useful in reducing the impact of this pest.
To learn more about lawn care, ground pearls and other lawn problems, visit the N.C. Cooperative Extension’s TurfFiles website at www.TurfFiles.ncsu.edu or https://sampson.ces.ncsu.edu/categories/lawn-garden/.
Disclaimer: The use of brand names and any mention or listing of commercial products or services in this publication does not imply endorsement by North Carolina State University nor discrimination against similar products or services not mentioned.
Brad Hardison is an agricultural extension agent specializing in horticulture. Contact Brad by calling the Sampson County Extension Center at 910-592-7161 or by emailing [email protected]