Don’t Want Those Pearls
Ground pearls, that is. Ground pearls are scale insects that suck fluids from the roots of bermudagrass, bahiagrass, St. Augustinegrass, and zoysiagrass, but prefer centipedegrass. They may be associated with acidic soil and are some of the most damaging pests of turf throughout the southeast. It’s the ground pearl nymphs that do the damage by extracting juices from underground plant parts.
Ground pearl injury shows up first as a yellowing of the grass, followed by browning in roughly circular patterns from a few inches to a few feet. Attack to the roots may cause circular dead areas that resemble fairy ring. The damage becomes most evident when the grass is under stress due to drought, nutritional deficiencies, etc. Stressed out lawn plants may not be able to tolerate ground pearl feeding damage and die as a result. The dead areas expand slowly, by up to a foot each year. If grass is replanted in these spots it usually dies within a year.
Turf infested with ground pearl is often impossible to get healthy again because there are no biological and chemical controls management strategies, including, that are currently available for ground pearls. Even taking out the top few inches of soil or killing the grass with herbicide in an infested area won’t be enough to reduce ground pearl infestations. The waxy coating surrounding the insect helps it to survive almost any adverse condition.
Keep in mind that there are other factors, such as disease, nutritional imbalances, drought, and nematodes (especially in centipedegrass) that can cause off-color areas in lawns. The lawn should be carefully examined to determine what the actual problem or problems are in order to apply the corrective measures needed.
Verify that ground pearl infestation is the actual problem by digging in the soil 3” to 4” deep around the edges of dead areas. Look for small, round insects that are pearly white to tan in color, similar in appearance to the pellets of slow release fertilizer found in container grown plants. Ground pearls occur in clusters, so check several locations before ruling ground pearl out.
As weeds tend to invade infested areas, there are some tactics that you can employ that will be of use. Well managed lawns often do not show noticeable damage, even though they may be heavily infested with these insects. Reduce the amount of stress the grass plants experience and keep up appropriate fertility and irrigation to help grass tolerate the damage. Additionally, you may consider redesigning the landscape in the infested area with more garden beds, and less susceptible grass varieties to remove the ground pearls’ food source. Practice good sanitation and clean- up of your tools and equipment. The movement of soil and contaminated equipment is the main way ground pearl are spread over large areas.
While all of the turf grasses grown in our area are susceptible to ground pearl, centipede is the most sensitive. Centipede lawns infested with ground pearl should be redesigned or converted to a more tolerant lawn grass. NCSU turf trials indicate that ‘El Toro’ zoysia tolerated ground pearl damage better than other species in the study. Though often considered a weed, bahiagrass has also been found to be relatively resistant to ground pearl damage. Very vigorous turf grasses like ‘Celebration’ bermuda can be grown in ground pearl infested areas if they receive supplemental irrigation and fertilization. This is more effective in heavy or clay soils. In deep sandy soils it is much more difficult to maintain a dense lawn if ground pearl are present, even when vigorous turf species are planted.
For more information about lawn care, ground pearls or other turf issues, visit www.Turffiles.ncsu.edu or the following sites: https://www.ces.ncsu.edu/depts/ent/notes/O&T/lawn/note64/note64.html
PLEASE help us better understand your needs as a gardener! Take an online survey at http://go.ncsu.edu/leecountygardensurvey. Targeted training and other programming will be developed based on your input. Let us know how we can best serve you.
Disclaimer: The use of brand names and any mention or listing of commercial products or services in the article does not imply endorsement by North Carolina State University nor discrimination against similar products or services not mentioned.
Minda Daughtry is Horticulture Agent for North Carolina Cooperative Extension in Lee County.