Bermudagrass scale, rhodesgrass mealybugs, and ground pearls are infrequent insect pests of turfgrass and primarily occur in the Sandhills (midlands) and Coastal Plain of South Carolina. These insect pests may be difficult to find because their feeding sites are on roots or lower portions of the turfgrass. If not properly managed, all three can cause extensive damage to turfgrass.
Bermudagrass scale (Odonaspis ruthae)
Bermudagrass scale is an armored scale that is quite small (0.06 inch), white, and clam-shaped. Female scale body covers are rounded, whereas the male scale covers are more elongated. They attach to and feed upon the turfgrass stolons (runners), crowns, and stems of centipedegrass, St. Augustinegrass, and bermudagrass.
The adult female produces pinkish eggs beneath the hard body covering. There may be two generations per year in South Carolina, and the eggs hatch in March to May and July to November. The hatchlings (or crawlers) will seek a new location to settle down and begin sucking the plant sap and its nutrients. Then, they molt into the mature, immobile, clam-shaped form that is more easily seen.
With a heavy infestation, the lawn will be stunted and appear drought-stressed. If the lawn is under other stresses, such as improper fertilization or liming, improper irrigation (especially drought), or shade, the combination of scale injury and stresses may result in the death of the lawn. The build-up of thatch in the lawn provides a more protected and shaded environment for the scales to thrive.
Rhodesgrass mealybug (Antonina graminis)
Rhodesgrass mealybug has a wide range of host grasses but primarily attacks St. Augustinegrass, bermudagrass, and centipedegrass. There are multiple generations per year, and the eggs may hatch from spring through fall. Both the nymphs (immatures) and the adults damage turfgrass by feeding on plant sap beneath leaf sheaths on stem nodes, at the base of stems, and in the crowns. They feed by piercing-sucking mouthparts, which removes a large amount of nutrients and water, leading to poor growth and a stressful condition for turfgrass. Primarily, adults will be noticed because of the white, fluffy, waxy body covers and the long wax filaments they produce. Mealybugs produce copious amounts of honeydew waste (a clear, colorless, sugary exudate), which becomes covered with a gray or black sooty mold. The honeydew is attractive to ants, including fire ants, which feed upon this sugary substance.
Turfgrass infested with rhodesgrass mealybugs will become discolored and wilt. Damage is generally greater with summer heat and drought stress, especially in sunnier parts of the lawn. Heavily infested turfgrass areas under severe drought stress may die.
Ground pearl (Eumargarodes laingi)
Ground pearl is a small scale-like insect that feeds on turfgrass roots and occurs in much of the warmer parts of the Southern U.S. They are a problem on home lawns and may infest bermudagrass, St. Augustinegrass, centipedegrass, and zoysiagrass. Damage to centipedegrass is often more severe than to other grass species. Pinkish female adults appear in late spring or early summer, and eggs hatch over a long time (May through July). Immatures (nymphs) begin feeding on rootlets and then encrust themselves in white or tan, waxy ‘pearls’ that may be as large as 1/16th-inch in diameter.
Turf damage begins in spots as a yellowing of the lawn, followed by browning and death, which may expand slowly each year. If the turf is under stressful conditions due to drought, very low mowing heights, excessive watering, improper herbicide applications, or improper liming or fertilization, this may result in more rapidly expanding dead areas in the lawn. In addition, weeds may invade these dead areas.
Cultural Control: Keep the turfgrass as healthy as possible to reduce stresses. This allows the turfgrass to better tolerate bermudagrass scale, rhodesgrass mealybug, or ground pearl infestations. Mow turfgrass at the proper mowing height. In the shade or during periods of drought stress, mow slightly higher. For the recommended mowing height of each grass species, please see HGIC 1205, Mowing Lawns. Bag the clippings, and then destroy or dispose of clippings after cutting to aid in pest control.
Test the soil to determine proper fertilizer and lime requirements. For best growth, the soil pH should be between 5.5 and 6.0 for centipedegrass and between 6.0 and 6.5 for bermudagrass, St. Augustinegrass, and zoysiagrass. For soil test directions, please see HGIC 1652, Soil Testing.
Fertilize each turfgrass based on soil test analysis and recommendations, and typically fertilize turfgrass about May 1st and again in early July.
During periods without rainfall, water the lawn one time per week during the spring and fall with 1 inch of irrigation water. Watering may need to be a little more frequent during the intense heat of summer, with ¾ inch of irrigation water every 3 to 4 days on sandy soils. Always water the lawn in the early morning. For more information on home lawn irrigation, please see HGIC 1207, Watering Lawns.
If needed, dethatch warm-season lawns once the lawn completely greens up in early May. However, with insect infestations by these pests, dethatch any time during the growing season after determining that one of these three is causing the lawn damage. The dethatching physically helps remove some of the adult insects. Dethatch and remove the debris from the uninfested portions of the lawn first. Then dethatch the infested portion but be careful not to spread the removed thatch from infested into uninfested areas. For more information on dethatching lawns, please see HGIC 2360, Controlling Thatch in Lawns.
Do not apply post-emergence herbicides to damaged lawns unless needed, as this causes additional stress to the turfgrass. Do not apply preemergence herbicides during the latter part of spring to weak lawns that need to fill in, as these herbicides will inhibit the rooting of turfgrass. For more information on turfgrass weed control, please see HGIC 2310, Managing Weeds in Warm-Season Lawns.
Turfgrasses grow best in full sun. If necessary, limb up nearby trees and prune back overhanging shrubs to increase light levels.
Proper cultural care of the home lawn will help the grass outgrow or survive a bermudagrass scale, ground pearl, or rhodesgrass mealybug infestation. If ground pearl damage is severe on centipedegrass, consider replacing it with bermudagrass, bahiagrass, or carpetgrass, which are less sensitive to this pest. An alternative to battling weakened or dying turfgrass areas is to convert them into mulched shrub and flower beds.
Chemical Control: Currently, no insecticides are specifically labeled for the control of ground pearls. Bermudagrass scale and rhodesgrass mealybug are best controlled by applying a systemic insecticide (absorbed by the turfgrass) and a contact insecticide. Examples of products labeled for use on residential lawns that contain both types are:
- Aloft LC G, which contains clothianidin (systemic) and bifenthrin (contact),
- Allectus G, which contains imidacloprid (systemic) and bifenthrin (contact).
Aloft LC G is a granular product (40 lb bag), and applied at the rate of 3.6 lbs per 1000 sq ft. Allectus G is also a granular product (50 lb bag), and is applied at 2.9 lbs per 1000 sq ft. Make an Aloft or Allectus application in spring after total green-up of the lawn and again a month later. Apply ½ inch of irrigation water within 24 hours following each application to dissolve the granules. Aloft LC G and Allectus G are products that can be purchased at landscaper supply stores.
Alternatively, apply a systemic insecticide containing imidacloprid. Examples are:
- Ferti-lome Systemic Insect Spray RTS,
- Bayer BioAdvanced Complete Insect Killer for Soil & Turf RTS,
- Hi-Yield Systemic Insect Spray RTS,
- Martin’s Dominion Tree & Shrub Insecticide Concentrate (also labeled for use on the lawn with a hose-end sprayer)
These ready-to-spray (RTS) products are hose-end spray applicators that cover 3500 to 5500 square feet per bottle and allow for a thorough saturation of the turfgrass. An imidacloprid RTS product may also be sprayed on the turfgrass during the time of crawler activity (for bermudagrass scale or rhodesgrass mealybug) to lessen the infestation.
It may be difficult to totally eliminate bermudagrass scale or rhodesgrass mealybug from the lawn, but with proper cultural care, coupled with chemical treatments in the spring after total lawn green-up and again a month later, this will help the lawn outgrow and survive the infestation.