Adult southern chinch bugs are small and slender, 1 /6″ to 1 /5″ long with black bodies and white wings. Each wing has a distinctive, triangular black mark. Normally, some of the adults at any given site will have full-sized, functional wings, whereas other individuals will be short-winged and incapable of flight. Recently hatched immatures are wingless, yellow or pink, with a light-colored band across their backs. After each molt the nymphs more closely resemble the adults. Before the last molt, nymphs are black or brown, and have a white spot and two small wing pads on their backs. Chinch bugs are found most readily in the weakened, yellowing grass around a dead spot in the lawn.
Biology And Habits
In Texas, adult chinch bugs are inactive during the winter. Reproduction begins with warm weather in the spring. Under optimal conditions, each female can deposit up to 300 eggs, which hatch in 2 weeks. The nymphal stage lasts about 30 days, while the entire life cycle lasts 7 to 8 weeks. This speed of development allows time for three to five chinch bug generations each year. However, as the season progresses generations tend to overlap, with all stages found together. Mouthparts of the southern chinch bug consist of a long, slender beak, which is held close to the midline of the underside of the insect when not feeding. Chinch bug damage is due not just to the direct effects of feeding, but also to phytotoxic effects of the saliva.
Control of chinch bugs starts with proper lawn care. Proper irrigation is crucial to Chinch bug population control. Chinch bugs prefer hot, dry environments. Dry weather enhances survival of chinch bug nymphs and eggs by reducing the incidence of disease. Also, drought-stressed lawns are more susceptible to chinch bug injury. Keeping thatch to a minimum, for example, reduces chinch bug numbers and makes other control methods more effective. Thatch provides a protective home for chinch bugs, and chemically binds with many insecticides, making such controls less effective.
Excessive thatch forms when soil microbes are unable to break down dead plant material as fast as it is added. Proper mowing practices can help reduce thatch build up. For optimum turfgrass health, no more than 35 to 40 percent of the leaf blade should be removed at a time when mowing. This means that lawns generally should be mowed no less often than once a week during the growing season. Mulching- or recycling-type mowers tear grass clippings into small pieces that are decomposed more easily by soil microbes. Research has shown that proper use of mulching mowers reduces the need for fertilizers and does not contribute to excessive thatch. When thatch exceeds 1 inch in thickness, it may be necessary to have your lawn “vertically mowed.” Vertical mowing can temporarily harm your lawn’s appearance because it destroys the tightly woven stolon system of St. Augustine.
Lawn aeration with top-dressing also can help reduce thick layers of thatch. Aeration is performed by punching holes in the turf to increase air and water penetration. Lawn aeration machines can be obtained from many equipment rental stores, or aeration can be performed by a professional lawn care company. Aeration, in combination with top-dressing, helps correct moderate thatch problems by increasing soil-to-thatch contact, thus speeding up microbial decay. Too little or too much water also can cause chinch bug problems. St. Augustine lawns should be watched closely during the summer for signs of drought stress. The lawn should be watered immediately when edges of grass blades begin to curl, grass fails to spring back quickly when walked on, or the turf takes on a dull bluish-gray color. Due to the variety of soil types and depths in Texas, the amount of water needed will vary.
The most commonly planted St. Augustine-grass varieties are highly susceptible to chinch bug attack; however, research has identified several resistant types. The varieties ‘Floratam’, ‘Floralawn’, and ‘Floratine’ show varying degrees of resistance to feeding by chinch bugs. ‘Floratam’, however, is the only variety that is commonly sold in Texas. ‘Floratam’ generally provides a high level of resistance to both chinch bugs and St. Augustine Decline (SAD), a viral disease; however, it should be planted only in the southern half of the Texas because of it lacks cold-hardiness.
Chinch bugs are attacked by many predatory insects, such as big-eyed bugs, minute pirate bugs, and ants. Repeated insecticide applications can reduce populations of beneficial organisms and actually lead to increased chinch bug numbers. To preserve beneficial insects, apply insecticides only when necessary.