Chinch Bugs
The southern chinch bug, Blissus insularis Barber, is one of the most important insect pests of St. Augustine grass in Texas. It can be a problem anywhere St. Augustine grass is grown, causing most damage in the Gulf Coast region and in the southern half of the state.
Although it is a serious pest only on St. Augustine grass lawns, the southern chinch bug occasionally may feed on zoysia grass, centipede grass, bahia grass or bermuda grass. The common chinch bug, Blissus leucopterus leucopterus (Say), is a closely-related species that is a pest of grain crops in Texas and throughout the Midwest. This species also occasionally damages turfgrass and may be responsible for infrequent reports of chinch bugs in bermuda grass, fescue and zoysia grass lawns.
Identification
Chinch bug damage
Expanding, irregular patches of dead or stunted grass surrounded by a halo of yellowing, dying grass often provide the first clue of chinch bugs. These islands of dying grass tend to increase in size and merge as insect numbers increase. Damage can develop rapidly, especially in sunny locations during hot, dry weather.
Chinch bug damage can be confused with certain lawn diseases or other physiological disorders. For example, brown patch is a common disease affecting the leaf blades of St. Augustine grass. Brown patch symptoms, however, usually occur in a circular or semi-circular pattern, as opposed to the irregular-shaped areas of dead and dying grass that result from chinch bug feeding. Chinch bug damage also can be difficult to distinguish from that caused by drought. Detecting significant numbers of the insects themselves is the best proof of chinch bug damage. Chinch bugs are piercing sucking insects so normally you will see the blades have a twisted look like all the juice has been sucked out of them.
Adult southern chinch bugs are small and slender, measuring 1⁄6 to 1⁄5 of an inch long. They have black bodies with white wings, each of which bears a distinctive, triangular black mark. Normally, some of the adults at any given site will have full-sized, functional wings. Other ones will be short-winged and cannot fly. Recently hatched nymphs are wingless, yellow or pinkish-red with a light-colored band across their backs (abdomen). After each molt the nymphs more closely resemble the adults. Before the last molt, nymphs are black or brownish-black, and have a white spot and two small wing pads on their backs.
Biology and habits
Adult chinch bugs in Texas are inactive during the winter. Reproduction begins with warmer weather in the spring. Under optimal conditions, each female can deposit up to 300 eggs, which hatch in approximately 2 weeks.
The nymphal (immature) stage lasts less than 30 days during warmer weather, while the entire life cycle lasts 7 to 8 weeks. This rapid development allows time for three to five chinch bug generations each year. However, as the season progresses, generations tend to overlap, so all stages are found at the same time.
Mouthparts of the southern chinch bug consist of a long, slender beak, which is held close to the midline of the insect’s underside when the bug is not feeding. Chinch bug damage is probably due not just to the direct effects of feeding, but also to phytotoxic effects of the saliva.
Chemical control
Good cultural practices include water and fertility management, and thatch control. They dramatically reduce the need for insecticides to control chinch bugs. However, when dead and dying zones of turfgrass have chinch bugs, some corrective action is needed. While chemical insecticides can rapidly reduce chinch bugs when used according to label directions, most labeled materials do not last long and may require repeat application.
First determine whether a problem truly exists when considering pesticides for chinch bug control. If your neighborhood is prone to chinch bug problems, inspect your lawn weekly during the spring, summer and fall. Look for off-color areas, especially in direct sun, and along sidewalks and driveways. When there are numerous chinch bugs, they will cause grass to yellow. You can often find them by parting the grass at the edge of affected areas and by examining the soil and base of the turf. You should check areas with suspected infestations several times. When chinch bugs are numerous, you might see them on leaves or scurrying about on adjacent sidewalks during the day.
Liquid sprays are usually applied using a hose-end sprayer that can apply 15 to 20 gallons of water per 1,000 square feet. To ensure even coverage, spray back and forth across the same area. Watering the lawn before application can help the pesticide penetrate the turf, but irrigation is not recommended following application of liquid insecticides.
Use spot treatments where chinch bugs are restricted to isolated areas of the lawn. Treat the off-color turf and all surrounding infested areas. Inspect the site every 3 to 5 days for at least 2 weeks to determine if the infestation is under control. Spot treatments help prevent environmental contamination. They also minimize the impact of pesticides on beneficial insects.
Products that provide satisfactory control of chinch bugs include those containing carbaryl or any of the pyrethroid insecticides, such as bifenthrin (Maxxthor SC). Resistance to the insecticide bifenthrin has been identified among southern chinch bugs in parts of Florida, but has not yet become a problem in Texas.
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