Contrary to popular belief, insects are not a common cause of residential lawn damage in Modesto. Many insects
in the lawn are beneficial. Never apply an insecticide unless a damaging level of a known insect pest is
How to know if insects are causing damage:
- Brown spots in lawns can be caused by over or under watering, plant disease, and improper use of chemicals
or dog urine as well as insects.
- Confirm the presence of insects before applying an insecticide. For grubs, dig around roots, for other
insects perform a drench test.
- For instructions, call the UC Cooperative Extension Office (209) 525-6800 or go to
UC Davis Pestnotes.
Keep your lawn healthy by:
- Planting grass species that do well in you area.
- Watering deeply and infrequently.
- Doing routine maintenance on sprinkler heads.
- Applying only three to six pounds of actual nitrogen per 1000 sq. ft. each year when fertilizing.
- Aerating your lawn annually; remove thatch if it exceeds 1/2 inch.
- Cutting only 1/3 to 1/2 of grass height at each mowing and keeping lawnmower blades sharp.
If your lawn is damaged:
- Find out which insecticide ingredients target specific lawn insects then choose the right product for your pest.
- Bacillus thuringiensis (Bt) kills only caterpillars, including cutworms, lawn moths and skippers.
- Some nematodes control caterpillars or grubs.
- Azadirachtin controls cutworms, armyworms, and larvae of lawn moths.
- Imidacloprid is effective against young lawn grubs.
- Acephate and permethrin are broadly toxic pesticides that kill cinch bugs, lawn moths, and cutworms, but also kill beneficial insects.
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