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Chinch Bugs

These destructive lawn insects love sunny areas

By: Sandy Feather ©2010
Penn State Extension


Q. My sunny front lawn has a big brown patch in it. At first, I thought it was just the hot, dry weather, but I discovered these insects scurrying around in the dead grass. Could they be to blame?

A. The writer enclosed a sample of insects with the question. They are hairy chinch bugs (Blissus leucopterus hirtus), a common pest of lawn grasses, wheat, sorghum and other cereal grasses. They are classified as true bugs in the order Hemiptera (not all insects are “bugs” even though the term is frequently used that way). They undergo incomplete metamorphosis, which means that nymphs hatch from eggs, and undergo five instars (growth stages) until they molt into adult insects. They do not pupate. Nymphs are generally more susceptible to control than the adults.


CHINCH BUG IDENTIFICATION

Adults are roughly one-eighth of an inch long, with gray-black bodies and white wing covers sporting a black spot in the middle front edge. Nymphs start out reddish-orange with a white band across their abdomens, and darken as they grow. Depending on the instar stage, nymphs range in size from one-thirty second of an inch to adult size.

Chinch bugs are always worst in full sun, and in areas where heat is reflected from pavement and buildings. They really thrive in hot, dry weather. When infestations are severe, they can reach populations of 150 to 200 chinch bugs per square foot; researchers recommend treatment when populations reach 15 to 20 chinch bugs per square foot. Being true bugs, chinch bugs feed with piercing-sucking mouthparts. They inject a toxin into the grass blades as they feed which causes the grass to die. Injury is particularly severe when turf is dormant due to drought stress.

 


OVERWINTERING

Chinch bugs overwinter as adults in thatch, along the edges of paving and close to buildings. They begin actively feeding when temperatures reach 70°F. Adult females begin laying eggs roughly from mid-April until June. The eggs hatch anywhere from one to four weeks, depending on temperatures. First generation nymphs mature by mid-July. Their eggs hatch and a second generation matures from the end of August through September.

Before applying any insecticide, monitor your lawn for their presence. You can easily see chinch bugs scurrying around in the turf by getting down on your hands and knees and parting the grass. You will find the most activity where damaged turf goes into healthy turf. Another technique for monitoring their presence is to take a coffee can and remove the top and bottom lids. Push and twist one end into the ground where you think the chinch bugs are active. Fill the can with water and count the number of chinch bugs that float to the surface in 10 to 15 minutes. If the water drains into the soil before then, refill the can. If you find 20 adults per square foot, treatment is warranted.


WEATHER CONDITIONS

Mother Nature can help keep chinch bugs in check. When we have cool, wet spring weather, or cool, wet weather in summer, chinch bugs are often infected with a naturally occurring fungal disease known as Beauvaria bassiana. Infected chinch bugs appear covered with a white mold. You can help this process by keeping your lawn irrigated during hot dry weather. The added moisture favors the spread of Beauvaria and can help keep chinch bug populations down.

Other cultural controls include replacing susceptible grasses with endophyte-enhanced varieties. These grasses are infected with a beneficial fungus that make the grass unpalatable to surface-feeding insects such as chinch bugs. Avoid using endophyte-enhanced grasses if there is chance that livestock might graze there.


BEYOND PESTICIDES

Another least toxic option recommended by Beyond Pesticides is to apply diatomaceous earth to the affected area of your lawn. Diatomaceous earth works by piercing insects’ exoskeletons, causing them to dehydrate and die. Be sure to use diatomaceous earth labeled for insect control, rather than that sold for swimming pool filters. It is important to wear a dust mask when applying this product to avoid inhaling the particles.


CHEMICAL CONTROLS FOR CHINCH BUGS

If chemical control is required, carbaryl (Sevin), cyfluthrin (Bayer PowerForce Multi-Insect Killer), and imidacloprid (Bayer Advanced Season Long Grub Control, Spectracide Grub Stop Once & Done and others) are labeled to control or suppress chinch bugs in home lawns. Scout for chinch bug activity regularly and apply your insecticide of choice if they exceed the threshold of 20 per square foot as soon as possible. If you get good control of the first generation, you may not need to treat for the second generation. This is especially true if we are having adequate rain and Beauvaria helps keep them in check. Conversely, if we are having a very hot and dry summer, a second application may be necessary mid- to late August.


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