Chinch bug damage appears as expanding irregular patches of dead or stunted grass surrounded by a halo of yellowing grass. The damage generally occurs from June into September beginning in hot, sunny locations, often next to pavement. It looks similar to drought damage because both cause the plant to have restricted water intake. Common St. Augustine and ‘Raleigh’ tend to have the most chinch bug problems
Figure 1 - Chinch bug damage to lawn. Photo by Dr. James Reinhart
Chinch bugs feed by sucking plant juices and injecting a toxin that blocks the food and water conducting cells. Detection of significant numbers of the insects themselves is the best proof that chinch bugs are the cause of the damage. Another clue is the patches continue to become larger in spite of watering. Adults are small and slender; 1/6” to 1/5” long with black bodies and whitish wings. Recently hatched nymphs are wingless, pinkish red with a light colored band across their back.
Figure 2 - Chinch bugs feeding on plant juice, and adults and nymphs. Photos by Dr. James Reinhart
Testing for chinch bugs: Chinch bugs live in the thatch layer. Thatch is the layer of dead plant material that builds up between the turf foliage and the soil and is an indicator of poor management practices. The testing is best done early in the day.
- Cut the bottom out of a coffee can and work into soil in the yellowing area on or near the edge of the dead grass.
- Fill with water and continue to refill as needed for 10 minutes; if chinch bugs are present they will surface.
- Try more than one area and if you find between 2-5 chinch bugs in each test area treatment is recommended.
- Check your irrigation program settings and do a run through to make sure each station is running properly.
Least toxic solutions: Monitor regularly. Chinch bugs are relatively easy to control if they are detected early.
- Manage turf to prevent or eliminate the thatch. This includes aerating, mowing with a mulching mower, preventing drought stress and using low rates of slow-release fertilizer.
- Remove thatch with a rake or vertical mowing. Chinch bugs prefer at least ½ inch of thatch.
- Heavily infested lawns may have significant plant mortality because of the toxic effect of chinch bug saliva.
- For minor infestations try spot treating the area with insecticidal soap.
Regardless of the pest, the best prevention is having a healthy lawn. If problems do occur, proper identification is crucial to correctly addressing them. Always read the pesticide label and follow the directions for use and storage.
See the Grow Green Lawn Problems fact sheet for more information.
Article by Denise Delaney, Grow Green Program, Watershed Protection Department