The Chinch Bug Invasion

Entomology News and Information:
Turfageddon: The Chinch Bug Invasion

The Utah Plant Pest Diagnostic Lab received numerous turfgrass samples this summer. The drought of 2012 stressed some lawns, making pest issues common this year. Out of 163 samples submitted between April 1 and September 20, 2012, 37 (23%) were turf-related. Some of the diagnoses included necrotic ring spot (13 samples), summer patch (5), snow mold (4), moss encroachment (1), sod webworm (2), and Banks grass mite (1). The lab also identified chinch bugs in four separate samples; the first the lab has seen of this pest in over 6 years. Chinch bugs may be responsible for undiagnosed turf damage this year, and may be a continuing issue next year.

In general, chinch bugs rarely reach damaging numbers, but in severe heat and drought, they can become a problem in turfgrass. Chinch bug damage is most prevalent on perennial ryegrass, fine fescues, red fescue, bentgrass, and Kentucky bluegrass. Periods of drought and heat, coupled with under-irrigation, direct sunlight, and thick thatch can cause chinch bug numbers to soar from mid-summer into early fall.

Typical damage is patchy dieback that forms larger patches and in severe cases, complete lawn loss. Chinch bugs kill turf through mechanical damage to grass stems and by injecting saliva during feeding (piercing and sucking), which inhibits the transport of water within the plant. Feeding damage can often mimic drought stress; however, chinch bug damage will not respond to increased watering as a drought-affected lawn would. Feeding damage is often worse on plants that are already affected by drought.

The black and white chinch bug adults are very tiny, about 1/6 of an inch, and are not readily seen without close inspection. The nymphs are very small and bright orange with a pale strip across their backs. As they increase in size, wing pads develop and the orange coloration begins to disappear. By the time nymphs reach their 5th and final instar (developmental stage), they are mostly the same black color as the adults. Note that some individuals and populations of chinch bugs have small, or reduced wings as adults. Adult chinch bugs look similar to, and can easily be mistaken for, beneficial insects like the big eyed bug and the minute pirate bug.

Chinch bug turf damage can be severe in hot, dry conditions, as happened in Utah in the summer of 2012.

Adults overwinter in the turf thatch, along driveways, in foundation cracks, and in other hidden areas. They become active in the spring when temperatures start to climb above 50°F. Females lay eggs in turfgrass blades or in the thatch layer. One female can lay 300 eggs in her adult life, which can last several weeks. Egg hatch can take 20 to 30 days if temperatures are below 70°F, but less than a week when temps are over 80°F. The second generation will begin in July-August and numbers of chinch bugs can reach up to 300 per square foot in areas where conditions are ideal. Because eggs are laid continuously, almost every life stage can be seen at any time in the turf throughout the summer and fall.

Chinch bugs can be monitored by visually inspecting grass blades at the soil level and looking for all life stages. Because they are so small, a hand lens or magnifying glass may be needed to see them. On hot days, adult chinch bugs are often seen scurrying across concrete or brick surfaces or foundations. A monitoring trap can be made from a 6-inch diameter coffee can or similar object with both ends removed to create a metal cylinder. Push the can into the soil approximately 2 to 3 inches, enclosing the turf. Fill the can about ¾ full of water. Poke or stir the turf and thatch that is under water. Keep a constant depth of water in the can for about 10 minutes by pouring in extra water to replace the lost/leaching water. Count the number of chinch bugs that float to the surface. Treatment threshold is about 20-25 bugs per square foot, or about 4-5 per can. If numbers are below this threshold, regular irrigation and fertilization can mitigate chinch bug damage.

In Utah, chinch bugs seldom need insecticidal treatment unless the population has exceeded threshold levels and damage is evident. Effective insecticides include bifenthrin and other pyrethroids. For best results apply an insecticide in the spring during adult emergence from overwintering sites. Killing emerging bugs will limit the number of eggs laid in the first generation and help reduce the population size throughout the summer.

Preventive management practices include proper irrigation, regular fertilization, reducing thatch via power raking and core aeration, avoiding the use of broad-spectrum insecticides that can reduce beneficial insects, and overseeding or replanting a lawn using endophyte-enhanced grass seed. Endophyte-enhanced grasses have been inoculated with a beneficial fungus that grows within the grass, making it more resistant to certain insects and diseases through the production of alkaloid compounds. Endophytic perennial ryegrass is especially resistant to chinch bug feeding. If you suspect chinch bug, collect samples for identification. They could easily be confused with look-alike insects that are beneficial, including the big-eyed bug and minute pirate bug.


-Ryan Davis, Arthropod Diagnostician

References:

Cranshaw, W. 2004. Garden Insects of North America: The Ultimate Guide to Backyard Bugs. Princeton University Press, Princeton and Oxford.

Niemczyk, H.D., and Sheltar, D.J. 2000. Destructive Turf Insects: Second Edition. H.D.N. Books, Wooster, Ohio.

Heller, P. 2007. Chinch Bugs in Home Lawns. Penn State University Extension.

University of Rhode Island Fact Sheets: Chinch Bugs. 1999. University of Rhode Island Extension.

National Pesticide Information Retrieval System. 2012. Accessed on 9-17-2012.