Golf Course Management

JUL 2018

Golf Course Management magazine is dedicated to advancing the golf course superintendent profession and helping GCSAA members achieve career success.

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07.18 GOLF COURSE MANAGEMENT 63 We turf entomologists pride ourselves on our ability to develop successful manage - ment programs for various insect pests. But in the past 10 years, I have been frustrated and humbled by two pests of warm-season grasses: One is bermudagrass mite and the other, the focus of this article, is ground pearl. e name ground pearl is deceptive and disappointing — ground pearls are not beautiful, and they won't bring riches or happiness to your life as a golf course superintendent. An underground menace For an entomologist, ground pearls are unique and fascinating insects. As a special - ized group of scale insects, ground pearls share two important features with their scale insect cousins: they suck plant sap through a modi - fied, strawlike mouthpart, and they produce a waxy covering on their bodies (described below in the section, "Life stages"). ese two features represent significant challenges to de - veloping a good monitoring and management program for ground pearls. Ground pearls have a subterranean habit, which makes them difficult to detect. ey feed on the roots of grasses and other plants by inserting their strawlike mouthpart into the roots and sucking out cell contents, sap and nutrients. e removal of nutrients from roots gradually weakens the host plants. Unlike fall armyworm, which produces telltale thinning of the turf, ground pearl causes subtle damage that often takes years to show itself. In the early phase of infestation when ground pearl density is low, there are no ob - vious symptoms and infested turf can often tolerate the infestation. However, as ground pearl density increases, root systems become more severely damaged. Symptoms first ap - pear as irregular, thinned, chlorotic patches (Figure 1), which turn brown in the summer and die in the winter or never green-up in the spring. e greatest numbers of ground pearls can be found near the boundary between ap - parently healthy and chlorotic turf (3), and this is where superintendents suspicious of ground pearl infestation should sample. e symptoms of ground pearl infestation are very similar to those of drought stress and grub or nematode infestation. Many turf managers often do not detect the infestation until it is too late, or they incorrectly identify the problem as drought or nematode damage (and, therefore, employ the wrong management tools). A bane of warm-season turf Ground pearls can attack all warm-season turfgrass species, with centipedegrass being the most severely damaged and slowest to recover. I have seen centipedegrass lawns in Myrtle Beach, S.C., devastated while the neighboring bermudagrass, St. Augustine - grass or mixed-species lawns maintained their apparent health and vigor for a short time de - spite infestations. Ground pearl is not restricted to lawns. If golf course superintendents think they do not have to worry about ground pearls because they don't have centipedegrass roughs, they should think again. Ground pearls can be equally at home feeding on bermudagrass and zoysiagrass. If the infestation is not detected, diagnosed and managed in its early stage, ber - mudagrass roughs and fairways can be just as devastated as centipedegrass lawns over time. Although ground pearls can be found worldwide, there are only nine species in the U.S. Two ground pearl species are pests of warm-season turfgrasses, mainly along the sandy plains from North Carolina to South - ern California (2). Dimargarodes meridionalis is known to infest the roots of grapevines and grasses in the southeastern U.S., Arizona and California, and Eumargarodes laingi is a pest of grasses in the southern U.S. and of sugar - cane in Australia (likely introduced from the U.S.). I have found only E. laingi during sam - pling of turfgrass in South Carolina. Both D. meridionalis and E. laingi are native to North America and likely have similar biology. Life stages Ground pearls get their name from the layer of wax the nymphs (that is, immature insects) produce on the outside of their bod - ies. e layer of wax is deposited as yellowish, shiny, hardened balls (Figure 2). ese wax balls, sometimes called cysts, are usually 0.06 to 0.13 inch (0.16-0.32 cm) in diameter and are found 2 to 6 inches (5-15 cm) deep in the soil. e cysts protect ground pearls from ad - Figure 2. Cysts are the waxy balls produced by immature ground pearls for protection against the environment and natural enemies. Cysts also inhibit the contact of insecticide solutions with the ground pearls. Photo by Meg Williamson, Clemson University Plant and Pest Diagnostic Clinic

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