Control Lawn Grubs with Beneficial Nematodes

Is your lawn rolling back in a carpet-like fashion? Grubs could be to blame.

by Jessica Walliser

There’s one garden troublemaker that always seems to be on everyone’s mind this time of year: grubs. Grubs are the larvae of several members of the scarab beetle family, including Japanese beetles (Popillia japonica), May/June beetles (Phyllophaga species), Oriental beetles (Anomala orientalis) and Northern masked chafers (Cyclocephala borealis), to name just a few. Most are pale-colored and shaped like the letter C. Other grub species aren’t harmful to your lawn, but this small handful of species can cause significant damage.

Grubs live in the soil and feed on the roots of turf grass and ornamentals. If found in large enough numbers, they can cause noticeable damage to our lawns, though in most cases, their numbers aren’t significant and control isn’t warranted. Turf grass can handle up to 10 grubs per square foot. If you find fewer than that after digging up a square foot of sod and searching for the grubs, and no visible damage is evident, there’s no need to apply a control product.

When brown patches appear and the turf peels back in a carpet-like fashion, you have a grub problem in need of management. Grub damage is most evident in spring and fall because the grubs feed in the upper layer of the soil.

Although it takes an entomologist with a magnifying glass to tell the difference between each different species of grub, there is no need to actually determine which species is the culprit because one, easy-to-use, natural solution gets rid of all of them: beneficial nematodes.

Applying beneficial nematodes of the species Heterorhabditis bacteriophora to all lawn areas allows you to manage all these turf-munching grub species without resorting to chemical products. This can be done whenever nighttime temperatures are regularly over 45 degrees F and the soil temperature is over 65 degrees F, usually in mid-May where I live. Beneficial nematodes are microscopic creatures that come in a powdered form and are mixed with water and applied to the lawn via a hose-end sprayer. Two yearly applications spaced seven to 10 days apart are all that are necessary for safe, season-long grub control. Because the nematodes do not survive the winter, you’ll have to reapply each spring.

Beneficial nematodes are living organisms, so fresh stock must be purchased each year. Follow all label instructions carefully for best results. Beneficial nematodes are available through several online sources, including Arbico-Organics and Planet Natural, among many others.

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