Issue 12, August 1, 2017

Chinch Bug

Chinch bug damage is being found throughout Illinois. Numbers of chinch bugs build under drier conditions, allowing bugs to survive which would be killed by fungal disease under higher rainfall. Thatchy turf allows the bugs to escape fungus attack by living in the thatch, not coming into contact with the soil where the fungus is living.

Chinch bug is attacked by a naturally occurring fungal pathogen, Beauvaria bassiana. This causes all stages, eggs, nymphs, and adults, to be killed and covered with fine white fungal strands. In Illinois, we typically get enough rainfall throughout the season that the fungus controls the chinch bugs for us, free of charge.

The other factor in chinch bug abundance is nitrogen. Chinch bugs, along with many other sap-sucking insects, are healthier and reproduce more on plants containing high levels of nitrogen. Excess nitrogen fertilization results in many more chinch bugs than would normally be present. In addition, excess nitrogen tends to result in increased thatch.

Damaged turf is light tan in color, looking like straw. Adjoining lawns that have not received as much nitrogen fertilization typically show no damage. To find the chinch bugs, push the grass blades to the side with your fingers to reveal the crowns of the grass plants, and the bugs will be evident at the base of the shoots. Another way to scout for chinch bugs is to push a coffee can or similar can down into the turf and fill it with water. The bugs will pop to the water surface and accumulate around the edge of the can. The threshold for treatment is a solid line of chinch bugs where the water meets the can.

Chinch bug damage to turf.

Two species of chinch bugs attack Illinois turfgrass. Hairy chinch bugs are found in northern Illinois, where they attack Kentucky bluegrass, fine fescues, perennial ryegrass, bentgrass, and zoysiagrass. Common chinch bug occurs in central and southern Illinois and feeds on the same grass species, as well as field grain crops such as wheat, corn, and sorghum. Both are similar in appearance and habits.

Adult chinch bugs overwinter in the crowns of grasses. They become active in the spring. They are about 1/8-inch long, long oval-shaped, and are black and white, due to wing coloration. Some adults have short wings and appear black. Nymphs are bright orange with a white band, turning to black as they go through five instars (stages). First-instar nymphs are about 1/32-inch long and grow up to be 1/8-inch long fifth-instar nymphs.

Common chinch bug nymphs.

Control chinch bugs with a spray of bifenthrin (Onyx, Talstar), deltamethrin (DeltaGard), lambda-cyhalothrin (Scimitar), or trichlorfon (Dylox). (Phil Nixon)

Phil Nixon

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