What to Do if Grass Has Yellow Spots or Possible Chinch Bugs


Keeping a lawn green and lush requires a lot of time and energy, and the presence of yellow spots can be frustrating. Yellow spots can be remedied if the root cause is identified. Chinch bugs, grubs, iron deficiency and physical damage can all contribute to a yellowing lawn.

Chinch Bugs and Grubs

  • Chinch bugs are black with frosty-white wings that have triangular black patch-like markings at the middles of the outer margins. Adults can be either long-winged or short-winged and may reach a length of 3/16-inch. Nymphs that have just hatched are orange red with a whitish band across their abdomens. As they develop through their five growth stages, nymphs become more orange and grow wing pads. They feed on many different types of grass, including grass, leaving yellow and brown spots in their wake. Grubs are the larvae of Japanese beetles, June beetles and chafers. They are white with brown heads; Japanese beetle grubs and chafers have six legs, but June beetle grubs do not have legs. Grubs are usually seen lying on their sides curled into a C-shape in the soil beneath the grass. They cause grass to turn yellow by feeding on the roots.

Treatments for Chinch Bugs and Grubs

  • The best ways to get rid of grubs is to use beneficial nematodes or milky spore disease. For chinch bugs, a natural spray can be made. Mix equal amounts of a natural biodegradable soap, citrus soap and insecticidal soap. Then add 5 to 10 drops of peppermint essential oil, therapeutic grade. Add ¼ cup of the mixture to a 1-gallon sprayer filled with water and spray on the lawn, preferably in the late afternoon. For best results, water after spraying. Bugs tend to be attracted to unhealthy lawns, so keeping your lawn healthy with proper watering and fertilization can help keep the bugs away. Watering should be consistent and deep, approximately 6 inches into the soil. Fertilizing with organic compost can help to maintain good bacteria and provide needed nutrients naturally. Apply compost every 30 to 60 days during the summer.

Yellow Spots from Iron Deficiency

  • Iron deficiencies can also cause yellow spots to appear in your lawn. If your soil is highly alkaline, your lawn will be extra susceptible to a deficiency in iron. Your lawn’s proximity to driveways, sidewalks or concrete planters can also be a factor, since concrete has a tendency to absorb iron due to its high alkalinity. Grass suffering from an iron deficiency will turn yellow but will retain green veins within its blades. Five to 20 pounds of elemental sulfur per 1,000 square feet can be added to the soil to correct the deficiency. Be careful when applying, because it can stain concrete.

Other Causes of Yellow Spots

  • Keep in mind that most lawn grass will have a period of dormancy when the grass turns from green to yellow or brown. Dormancy is triggered by seasonal temperature changes. For instance, warm-season grasses go dormant in winter and cold-season grasses go dormant in the heat of summer. Turfgrass will also turn yellow due to physical damage, such as too much foot traffic, mowing with a dull blade, over-application of pesticides, gasoline spills and dog urine. If you have a problem with your dog urinating on your lawn, train it to use another area of your yard. The high nitrogen content of the urine causes the grass to turn yellow.

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