Grass roots attract grubs

By George McVey, Ph.D.
Contributing Writer
Union County Post

Grub

Q. As a new homeowner, I am trying to take care of my lawn and landscape with limited knowledge. I have heard about lawn grubs and that they can be devastating. What are they, when are they out, how do I find them, and how do I kill them?
A. Grubs are the immature stage of several beetles (Japanese beetles, June beetles, masked chafer, etc.) that can infest lawns and cause damage by feeding on the roots. Grubs are about an inch long, whitish in color with a tan-colored head, and can be found curled in a "c-shaped" position on the soil surface, just below the thatch. Grass that is damaged by grubs can be easily lifted since the roots are gone, and irregular brown patches will appear in the lawn. Injury usually appears in late August, September and into October.
Grubs seem to be periodic pests, attacking lawns irregularly from year to year. Rainfall and soil moisture are major factors that influence whether there will be damaging numbers or not. In summers with normal or above normal rainfall (and in irrigated lawns) grub populations increase. Well-maintained lawns next to ornamental plantings favored by Japanese beetles (such as roses or grapevines) are also more frequently attacked.
Lawns with heavy thatch may also contribute to large, localized populations of grubs. Japanese beetle grubs do not need to feed on grass roots to survive; they can also feed on decaying organic matter - thatch.
Preventive treatments for grubs are not recommended; populations may be low in a particular season. However, if you have determined you will need to treat for the next generation of grubs, there are two relatively new insecticides on the market that are quite effective.
One product contains the active ingredient imidacloprid (Merit), which can be applied from early June to mid-August for control of Japanese beetle and masked chafer grubs. Merit has to be applied before the new generation of grubs is discovered in August, and is therefore useful in lawns with a history of grub problems. Do not apply Merit earlier than mid-May, or it may not be effective by the time eggs hatch in late July to early August.
The other product is halofenozide or MACH2 (molt-accelerating compound halofenozide). Wait to apply this insecticide until early June. An advantage of this product is that it can be applied after the new generation of grubs is discovered in August, mid to late in the month. This is a more integrated pest management approach; targeting the pest population directly once it is discovered, and determined that control is needed. Several companies manufacture these products under different brand names.

Q. What are those scary-looking insects I am finding in abundance under the mulch? They are brown, have a big pincher on the rear end, and move fast! They are everywhere!
A. The insects you are describing are earwigs. Earwig populations build in wet springs, and this insect is now attacking various plants in gardens. Earwigs are nocturnal insects, and hide under mulch, low-lying leaves, containers, and debris during the day. If you suspect plant damage from earwigs, you may want to check your garden very early in the morning (1 a.m.-2 a.m.) to see if they are present and feeding. Earwigs are about one-half inch in length, and have a pair of pinchers on the rear end. Damage usually appears as irregular holes eaten in plant foliage or flowers, such as daisy and daylily. There are several species of earwigs, and not all are damaging to gardens; in fact, some are beneficial and prey on other insects.

Q. How can I control mosquitoes?
A. When heavy rainfalls cause standing water in lawns and gardens, mosquitoes may become a problem. Remove anything from the yard that allows water to collect and stand, thus eliminating mosquito-breeding sites. Change water in wading pools and birdbaths once or twice a week. Consider improving drainage in the lawn and garden where water may stand.
A natural "Bt" product is available to control mosquito larvae in standing water; Bacillus thuriengensis Berliner var. israelensis. This product targets larvae specifically, and is easy to use. It is available through some specialty gardening catalogs under several brand names and at some local garden centers.

Information submitted by George McVey, PhD. Union County Extension Program Assistant, Horticulture and Master Gardener Coordinator.
The information was taken from The Ohio State University Plant Facts Website.
The Master Gardener offers horticulture advice and tips, focusing on current issues, by volunteers who are with The Ohio State University Extension, Union County Master Gardener Program. For answers to gardening questions, call 937-644-8117 or e-mail mcvey.22@cfaes.osu.edu. Hours are 8 a.m. to 4:30 p.m. Monday through Friday.