As summer begins its transition into fall, a persistent pest is again taking up residence in many area lawns. Grubs. Just the mere mention of the name strikes an emotional cord. The emotion may be anger, frustration, disgust, but these white crescent-shaped insects have been a pain in our lawn for decades.
Grubs go by several names, including European chafer, white grubs, or just plain grubs. Entomologists call them Rhizotrogus majalis. Most homeowners call them a royal pain.
A new generation of grubs is just starting life. Remember those June bugs you heard and saw? They are the last generation of adult grubs, and they live in that stage just long enough to mate. The females then lay eggs a few inches into the soil. In two or three weeks, the eggs hatch and the tiny grubs begin feasting on the roots of your lawn. As they grow, and the soil turns cooler, they burrow deeper. After overwintering deep in the soil, the large grubs come back up in spring and feed until May when they pupate in the soil.
We recommend checking for grubs in your lawn in August. Cut one foot square sections of sod at several places in the lawn. Roll it back to reveal whether you have any grubs. If you have up to six or seven in per square foot section, they do not present a treatable threat. Treatment is recommended for eight or more per square foot. If you have a lawn service, they will check for grubs, and treat if necessary, as part of their service.
Imidacloprid (Merit) and trichlorfon (Dylox) are labeled for treatment of grubs in New York State. Beneficial nematodes are also available if you do not want to treat with a chemical. Treat early while the grubs are still small, and you will need less chemical to achieve control. As the grubs grow, more aggressive treatment will be required to manage them.
Control measures should be applied only in the fall, unless you have a very high grub population. In spring, the grubs are large and strong, and only feed for a short time before pupating. We may treat for those with a high population in the spring.
A note about June bugs. They are pesky but not harmful. They won’t bite or sting. In fact, they eat nothing in this stage of their lifecycle. Their size makes them intimidating to some people, and they fly in swarms. That, too, makes some people fear them. Then there is that noise as they collide with your closed windows and splat on your car windshield. But, rest assured that they will not harm you.