Blackwelder column: White grubs grow up to be June beetles

Thursday, October 01, 2009 9:53 AM  |  Printer friendly version | E-mail to a friend |

The Cooperative Extension Office had 10 large, white grubs in the hallway after the rains this weekend.

Wet soils forced them out of the ground to a drier location — unfortunately, under the doors and into our hallways.

These large grubs that were forced out of the ground with the rains were green June beetle larvae. These are the most common grubs found in lawns and plant beds, although there are many other types of beetle grubs lying just beneath the soil.

June beetle larvae are easy to identify because they crawl upside down on their backs with their feet upward.

Adult beetles lay eggs in late June and July which quickly hatch to small grubs. Japanese beetle grubs feed on grass roots, causing large dead spots in lawns. But June beetle larvae feed on decaying plant matter in the upper surface of the soil.

June beetle larvae are large, off-white grubs about the size of a person's thumb. Japanese beetles and other beetle larvae are much smaller and curl into a C-shape.

As these grub mature and grow larger, they burrow deeply into the soil, up to 8 inches, escaping cold, freezing temperatures. The deeper these insects burrow, the more difficult the control.

Now is the best time to control grubs while the soil is still warm. Beetle grubs can also be controlled in early spring in March and April, however, higher rates of insecticide must be applied.

Another reason to control grubs now is to eliminate the food source for moles. Moles feed almost exclusively on white grubs and other soil insects. Even though moles do not really do that much damage to the turf itself, most prefer not to have them in their lawn and shrub beds.

There are quite a few granular insecticides labeled for grub control in lawns and landscapes. Homeowners should use a fertilizer spreader to evenly apply the pesticide as you would any granular fertilizer on lawns and shrub beds.

It's best to apply granular insecticides just before a rain or irrigate after application. There is one exception: June beetle larvae can be controlled with Sevin wettable powder and should not be watered in after application.

After treatment, June beetle grubs may be found on the soil surface, whereas other grub species will die in the soil.

Darrell Blackwelder is an agricultural agent in charge of horticulture with the North Carolina Cooperative Extension Service in Rowan County. Call 704-216-8970.

http://www.rowanmastergardener.com

http://rowan.ces.ncsu.edu

http://rowanhorticulture.blogspot.com/