Dealing with Beetles & Grubs
The larvae of several beetle species – commonly known as white grubs – are major pests of turf grass throughout much of the U.S.
Significant species include
- Japanese beetles
- Oriental beetles
- Northern & Southern masked chafers
- Asiatic garden beetles
- European chafers
- May or June beetles
Grubs live in the sub-surface layer of soils and in thatch layers in the lawn. They live in sunny lawn areas and especially on sloped, well-drained areas, preferring heavily-thatched layers. Generally, grubs can be found in soils most times of the year, but usually in small numbers (0 - 5 per square foot) and aren't considered a problem. When grub populations become heavier, their larva will feed on the root system, causing injury to turf grass. Infested areas will first turn pale, then yellow, then brown, finally dying. Areas of affected turf can be lifted easily from the soil (like a piece of carpet). In addition, moles, raccoons, skunks, birds, and other animals love to feed on white grubs, and as they forage for them in the infested turf, they can cause significant turf damage.
While the larval grub stages are similar in appearance and can be characterized by the C-shaped position when found in the soil-thatch area of the turf, when in the final, adult, beetle stage they'll differ in size, color markings and life cycle. Typically, the adults emerge in mid-summer, often after significant rainfall or watering, after which they'll mate and lay eggs. Depending on species and region of the country, the beetles may lay eggs at various times during the season, but it usually begins in late June or early July, and continues through summer. After hatching, the small larvae begin feeding on roots, but most of the feeding damage is caused by the comparatively large, third-instar larvae (there are 3 'instar' larvae stages), and it's this stage that visible turf damage usually occurs.
During late October or November the third-instar stage larvae will move deeper into the soil for protection from cold weather, and they'll stay there for the Winter. The following Spring, they'll move closer to the surface to feed and replenish food reserves lost during the winter months before moving back down and transforming into the pupil stage. Little if any visible turf damage occurs at this time. This one-year cycle is complete when the beetles emerge from this pupil stage a short time later.
Ways to control white grubs
- • Relieving compacted soil, decreasing thatch, and improve root system through annual core aeration
- Maintaining good soil fertility to help improve the health and competitive ability of your grass
- Applying grub preventative treatment to the lawn at the appropriate time
- Watering (irrigating) your lawn the right way, giving your lawn the right amount of water at the right time
- Beetles are attracted to certain dark-foliated (and flowering) trees and plants (roses, crepe myrtle, rose-of-sharon, etc.)
- Inspecting suspicious turf by grasping the turf firmly with two hands and trying to pull it up.
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