A warm season turfgrass, zoysia grass spreads through stolons and rhizomes to form a dense, green lawn. It has low water requirements and can tolerate periods of drought. The grass does go through a period of dormancy during the winter, when it will loose its green coloration. Highly disease resistant, the major threat to the overall appearance of zoysia grass are Southern chinch bugs (Blissus insularis).
The Southern chinch bugs thrives in areas of zoysia grass that receive full sunlight. The insects enjoy sucking the nutrients and water from the grass blades, leaving areas of the zoysia grass yellow and dead. The insects live and feed in large colonies, so ever-growing areas of the grass will begin to appear dead. During voracious feeding, the insects inject a toxin into the grass blades with their mouth, making the grass unable to absorb nutrients, according to the University of Missouri. The most severe turf grass damage from Southern chinch bugs occurs from April to October.
Three to four generations of chinch bugs will prosper on zoysia grass if not controlled. The eggs of the bugs are laid beside the grass sheaths and pushed just beneath the soil to afford protection. In 10 days the eggs hatch into tiny nymphs that feed heavily on the zoysia grass. The nymphs pupate into adults after approximately four weeks and the cycle is repeated. The adult chinch bugs also feed on the grass prior to breeding.
In areas of the zoysia grass where chinch bug infestations are suspected the homeowner can pull up sections of the dead lawn to look for the insects. The adult insects appear glossy black with patches of white on their wings. Each adult measures only 3/16 of an inch long. The newly hatched nymphs measure only 1/16 of an inch long and are orange in coloration with a white band around their back.
All varieties of zoysia grass are susceptible to chinch bug infestation. Chinch bugs prefer hot, dry grass, which is why they thrive in zoysia grass that receives full sunlight. Excessive watering of cinch grass will help prevent chinch bugs. Fall removal of thatch also will reduce the incidence of chinch bugs, since they overwinter in the thatch accumulation in the lawn.
If the zoysia grass suffers from a heavy infestation of the southern cinch bugs, pesticide applications may be required. The insecticides bifenthrin, carbaryl and lambda-cyhalothrin have shown success at controlling cinch bugs, according to the University of Nebraska--Lincoln. The zoysia grass should receive ample irrigation after the insecticide application.