Blackwelder column: Grubs coming out due to recent rain

Published 12:00 am Thursday, September 29, 2011

SALISBURY — Many homeowners have called complaining about grubs. 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.
In late June and July, adult beetles lay their eggs, which quickly hatch to small grubs. Japanese beetle grubs feed on grass roots, causing large dead spots in lawns. However, 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 grubs 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 it is to control them. 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, but 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. The insecticide is easily applied with a fertilizer spreader that evenly applies the pesticide as you would any granular fertilizer. It’s best to apply granular insecticides just before a rain or to irrigate after application. However, 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.
There are products that use bacteria to kill grubs, but it only kills the Japanese beetle grub. Milky spore bacteria infects the grubs and produce a disease killing the grub. These spores work best when applied in late September or early October to soil with a pH level between 6 and 7. This product is available at many garden shops and retail outlets. Go to http://www.turffiles. ncsu.edu/articles/tf00506.aspx for more in-depth information about grubs and their control.
Darrell Blackwelder is the County Extension Director with horticulture responsibilities with the North Carolina Cooperative Extension Service in Rowan County. Learn more about Cooperative Extension events and activities by calling 704-216-8970 Facebook or online at www.rowanextension.com

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