Chinch bugs
Click for larger image Diagram of chinch bug stages (Hemiptera). A. Cushman, USDA; Property of the Smithsonian Institution, Dept. of Entomology, Bugwood.org

Chinch bugs, true bugs in the order Hemiptera, can cause significant damage to Midwest lawns, especially in areas that tend to be hot and dry in summer. Commonly damaged turf grasses in the St. Louis area include perennial ryegrass, Kentucky bluegrass, zoysia grass, Bermuda grass, and tall fescue. Chinch bugs feed by inserting their piercing mouth parts into blades of grass and sucking out the juices. During feeding, they inject a toxin that continues to wilt and yellow the grass even after the chinch bugs are no longer present.

Symptoms and Diagnosis

The first sign of damage is the appearance of 2- to 3-foot diameter irregular shaped yellow patches in areas of the lawn that tend to become stressed by heat and drought. Sunny, south facing slopes and areas bordered by pavement are particularly vulnerable to attack. A heavy infestation can cause the entire lawn to develop a droughty, brown appearance.

Life Cycle

Adult chinch bugs emerge from winter hibernation in spring and mate when air temperatures reach 70° F. The adult is 1/5 inch in length with light colored, crossed forewings and a conspicuous black triangle midway along the thorax (shoulder). Newly hatched wingless nymphs are smaller, with red and white bands along the back, and darken in color from red to brown to black during their 3-4 week transition to mature adult. Adults and nymphs feed on turf grasses until cold weather arrives in fall, when the adults prepare for hibernation by burrowing into plant debris along building foundations and in the thatch layer of the lawn.

Integrated Pest Management Strategies

1.Supplemental watering. Since they prefer hot, dry conditions for optimum feeding, irrigating the lawn during hot, dry weather periods can reduce chinch bug populations. One to 2 inches of water/rainfall per week is considered adequate.

2. Plant resistant turfgrass varieties. If it becomes necessary to reseed damaged lawn areas, seed with chinch bug resistant varieties. Those supplemented with endophyte (beneficial fungi) may have even greater resistance to chinch bug damage.

3. Remove excess thatch from the lawn in fall. This destroys winter hibernation sites, decreasing adult and nymph populations and egg laying.

4. If necessary, use chemical insecticides. Do not use chemical insecticides as a preventive measure, but if lawn damage is not manageable with cultural means, insecticides are a viable option. Trichlorfon (Dylox), bifenthrin, and carbaryl, are recommended for home use. Always be careful to read the label directions fully before applying any pesticide, and follow directions completely. Other products are registered for use by commercial applicators.

Organic Strategies

Strategies 1, 2, and 3 are strictly organic approaches.

More images:

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Young chinch bug nymph (Hemiptera) on rice (Oryza sativa). N. Hummel, LSU AgCenter, Bugwood.org
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Older stage chinch bug nymphs (Hemiptera) on rice (Oryza sativa). N. Hummel, LSU AgCenter, Bugwood.org
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Chinch bug (Hemiptera) damage on zoysia grass. Image from "Issues with zoysiagrass lawns," Missouri Environment and Garden, (April 30, 2012).
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Chinch bug nymph (Hemiptera), a pest of zoysia grass lawns. C. Olsen, USDA APHIS PPQ. Bugwood.org