AUGUSTA—With melting snow and ice, rising temperatures and the arrival of lawn and gardening season, the Department of Agriculture, Conservation and Forestry (DACF) is advising homeowners to do their homework before attempting to manage lawn grubs. DACF is seeking to reduce unnecessary, ineffective pesticide use to manage these pests. Many resources are available through the University of Maine and the Maine YardScaping Partnership to make this homework light.
As lawns begin to turn green, homeowners often notice patches and larger sections of grass that are brown and dead looking. Frequently, they conclude the browning is caused by grubs and run out to purchase grub control products. Even if the damage is, in fact, being caused by grubs, the latest scientific research indicates that spring is not the best time to manage a grub problem.
“Springtime is not the best time for grub control,” says Jim Dill, manager of the University of Maine Cooperative Extension Pest Management Office. “As they emerge from winter, grubs are mature and this is when they are least susceptible to pesticides. Wait until early-May to mid-June to apply chlorantraniliprole (AceleprynTM and GrubEx1TM) and early-June to early-July to apply the other grub-control products, depending on the product and the location in Maine. This will allow the insecticide to be fully incorporated into the soil to control the new grubs which are just hatching, are closer to the surface, and are more susceptible to the effects of pesticides. Homeowners trying to control grubs in the spring are simply wasting their time and money. And, when they don’t seem to be working, there’s a tendency to over apply control products, and that’s when excess chemicals run off into our water supplies, and can be harmful to human health and the environment.”
Browning lawns can have a number of different causes:
“Before you do anything, there are some important points to consider,” adds Dill. “First, you must be sure that grubs are the problem. Browning lawns can also be caused by drought, poor soil, disease, or other organisms. And, even if the grubs are positively identified, are they in sufficient numbers to really cause significant damage? Sometimes, reseeding the brown patches is all that can be done. There are also biological controls, like beneficial nematodes, that may have some limited success. If you contact us at the Pest Management Office, we can help you identify your problem, provide many options for solving it and give you the proper timing to apply a specific control product in your area.”
Grubs—the white, immature, C-shaped form of beetles, most notably Japanese beetles and European chafers—feed on the roots of grass and cause the browning that we see. Knowing the grub’s life cycle is critical in determining if you have a problem, what to do about it, and when. From beetles emerging from the ground in early summer, through three distinct stages of grubs ending in the fall, keeping track of grubs can be difficult. The lawn damage you see in the early spring is actually the result of late summer, fall, and winter feeding. When the grubs are fully grown in the spring, they continue to feed for a short time and change into the pupal or resting stage which is not susceptible to insecticides.
Because it can be so tricky to figure out precisely what time is best for controlling grubs and which of the many available products to use, enlisting the services of a lawn care professional may be the surest course to take. They are specialists in treating just this type of problem and will identify exactly what’s going on with your lawn. They know what works, what doesn’t, and what is the best time for treatment—or if it’s needed at all.
“When grub-control products are applied at the wrong time, not only do they not work, but many, many pounds of pesticide products are being applied that don’t need to be and they can end up where they shouldn’t,” says Deven Morrill, member of the Board of Pesticides Control and arborist at Lucas Tree Experts, a Portland-based company that also does lawn care. “Just as professionals do, when homeowners apply products to their lawns, it is most important to read the label carefully, follow it exactly, and be sure it’s the right product for the problem at hand, applied at the most effective time. Licensed applicators stay tuned to the latest research and only apply products when they are proven effective.”