Contrary to popular belief, insects are not a common cause of residential lawn damage in California. Poor lawn care, especially improper watering and planting inappropriate grass species, are more likely causes of unhealthy or dying lawns. Disease-causing agents, excess or inappropriate use of chemicals such as fertilizer and herbicides or dog urine also produce lawn damage resembling that of insects. Many insects in the lawn are beneficial. Never apply an insecticide unless a damaging level of a known insect pest is confirmed. Insecticides are only effective if applied at the right time and in the right matter. Some insecticides may kill good buys too.
How do you know if insects are causing damage?
- Brown spots in lawns can be caused by over – or under – irrigation, plant disease, improper use of chemicals, or dog urine as well as insects.
- Confirm presence of insects before applying an insecticide. For grubs dig around roots and for other insects perform a drench test.
How to Perform a Drench Test:
- Mix 3-4 tablespoons of dishwashing liquid to 2 gallons of water.
- Evenly apply the 2 gallons to 1 square yard of your lawn.
- Monitor the area for 10 minutes and count the number of armyworms, cutworms, or lawn moth larvae that rise to the surface.
- Treat the area only if insect numbers exceed 5 armyworms or cutworms or 15 lawn moths per square yard.
If a Damaging Level of Insects is Confirmed, Do the Following:
- Choose an insecticide based on the pest you’re targeting
- Find out which insecticide ingredients target specific lawn insects:
- Bacillus thuringiensis (bt) kills only caterpillars, including cutworms, lawn moths, and skippers.
- Insect-attacking nematodes control caterpillars of grubs.
- Azadirachtin controls cutworms, armyworms, and larvae of lawn moths.
- Imidacloprid is effective against young lawn grubs.
- Pyrethroids (e.g. cyfluthrin, bifenthrin) are broadly toxic insecticides that kill chinch bugs, lawn moths and cutworms, but also kill beneficial insects and should be avoided.
Keep Your Lawn Healthy By:
- Planting grass species that do well in your area.
- Irrigating deeply and infrequently.
- Doing routine maintenance on sprinkler heads.
- Appling only 3 to 6 pounds of actual nitrogen per 1000 square feet per year when fertilizing.
- Aerating your lawn annually; remove thatch if it exceeds ½ inch.
- Cutting only one-third to one-half of grass height at each mowing and keeping lawnmower blades sharp.
And thank you for making me Your Orange County Real Estate Connection.
Michael Caruso, Broker ABR ABRM CLHMS CRB CRS GREEN GRI
Past President, Orange County Association of Realtors (949) 753-7900