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Stormwater Pollution Prevention

Lawn Insects

Stormwater Pollution Prevention

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 confirmed.

Lawn Pests

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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