Ground Pearls are an insect classified as part of the scale family of insects although they secret a waxy like substance instead of scales. In the early summer the tiny pink females will hatch from their bulbous waxy like covering which resemble tiny pearls and lay eggs underneath your sod grass. The nymphs then hatch given the right conditions and their sharp mandible mouths attach to grass roots and suck out the juices. The nymphs then begin to secrete their own waxy covering and retreat to their ground pearl covering during winter. If the conditions are not conducive to hatching, the eggs can lay dormant for several years.
On the surface, the damage resemble a fairy ring. A large irregular circle of yellowing, then browning, and eventually dead sod grass. The insects are tiny but are large enough to be seen with the naked eye. If you suspect you may have a ground pearls infestation, dig the sod grass up at the outer most edge of the circle where the sod is turning yellow. Ground pearls will be observed attached to the sod grass roots. 
Ground pearls are very hard to eradicate. There are currently no known insecticides which kill the insect, although natural predators like ants may be used to control populations. Proper maintenance of your sod grass helps keep your sod healthy making it naturally more resistant to disease and insects. St Augustine, Bermuda, Bahia and Zoysia Grass are all susceptible to ground pearls. Studies have shown centipede grass is the most vulnerable to a ground pearl infestation. If you live in an area prone to the insect consider installing a different species of sod grass or removing the sod and soil to incorporate a plant or tree into the landscape. Ground pearls only attach themselves to sod grass roots and do not cause damage to plants or trees.