Lawn: insect pests
Scout for problems before you treat.
Lawns are home to many, many insects. Very few of them are harmful, and many are even beneficial.
Healthy grass plants can tolerate some feeding by the harmful insects. But when the number of pests reaches a certain level – called a threshold – the quality of your lawn can be hurt. The open spaces the pests create in turf can be ugly, vulnerable to erosion, and invaded by weeds.
Most pesticide applications made to home lawns aimed at killing insect pests are either unneeded or ineffective. To make sure that you need a pesticide, you must first “scout” for the pests to see if there are enough of them to justify the treatment. If you do treat, you need to make sure that you apply the pesticide correctly and at the right time.
For example, treatment for Japanese beetle grubs isn’t justified unless there are more than 10 grubs per square foot. Unless someone peels back the sod at several locations and checks to see how many larvae are feeding on grass roots, you won’t know if the pesticide is needed.
In spring, grubs are usually too mature to be controlled by pesticides. Scout for grubs in late summer and early fall to determine if treatment is necessary while the grubs are still small enough to control. (If treatment is justified, August is usually the best time.) Because they feed below-ground, insecticides need to be watered in before they dry on grass leaves to be effective.
Similarly, scout for surface feeders (such as cutworms, sod webworms, chinch bugs and bluegrass billbugs) before treating.
Regardless of the pest, the best way to minimize damage is through prevention:
- Keep turf healthy through proper mowing, watering and fertilizing. Healthy turf will tolerate more pests.
- Plant the right grass for your location. Choose grasses that resist pests, such as endophytic varieties of perennial ryegrass, fine leaf and tall fescues. (Endophytes are beneficial fungi that live on the grass and discourage surface feeders.)
- Scout before you treat. If you use pesticides, treat when the pest is most vulnerable, and follow all directions carefully. To prevent water pollution, never apply pesticides when ground is frozen or saturated. To prevent drift and volatilization (which releases pesticides into the air), do not apply when temperatures are high or it is windy.