During the hot summer months in Florida we often receive questions regarding dead brown patches in St. Augustine lawns. It is often incorrectly assumed, since our summers are so wet, that fungus is to blame. Most residents are unfamiliar with the following symptoms of a chinch bug infestation.
Chinch bugs are tiny, about 1/10 to1/8 inch long (Chinch bug pictured above). They often scurry out of sight when the grass is disturbed, making them difficult to spot. Chinch bug damage usually appears first in hot sunny areas as small brown areas that gradually enlarge as the bugs move out of dead spots and into green turf, especially in grass that has been over-fertilized and contains more thatch. At this stage it is recommended that the chinch bugs be spot treated with a pesticide specifically labeled for chinch bugs. When spot treating, always treat a 10 to 15 ft. buffer area around the affected turf rather than blanketing the entire lawn with pesticide. Be sure to follow label directions when using any pesticide.
Most populations of chinch bugs have developed some level of resistance to most homeowner pesticides making a single application ineffective. Additionally, chemicalsthat are effective against chinch bugs do not kill the Chinch Bug eggs so a new population may emerge anytime up to 6 weeks after application of a pesticide. It is important to rotate use of pesticides with different modes of action to prevent resistance. While natural enemies such as the Big-Eyed Bug (pictured below) do exist, they are usually not abundant enough to provide a satisfactory level of suppression.
For more information on chinchbug management in St. Augustinegrass lawns, please see the UF/IFAS publication at the link below: