June Beetles and White Grubs
While walking across a grassland or turfgrass in the early parts of the growing season a person may occasionally observe some dead patches of grass. Some of these patches of dead grass even appear to have been dug up by some animal. What is going on here?
Some of those dead spots may be due to June beetles, or what some of you know as June bugs. I have noticed a few in our area recently. Most everybody is familiar with this insect, but not so much when it comes to their life cycle and ecology.
Most species of June beetles have a three-year life cycle in which the larvae spend most of three growing seasons underground feeding on the root systems of plants. As the common name indicates, the adults are active around early June. Following mating, the females lay their eggs in the soil. After the eggs hatch, the larvae spend the better part of the next three years, chewing up plant roots while passing through three instars or developmental stages. The final stage of these larvae is commonly known as a “white grub.” They are white to cream colored with a dark posterior, a little over an inch long, and curled up, or “C-shaped.”
Adult June beetles feed on the foliage of various trees and shrubs. In pastures in our state, a common food item is western snowberry, also known as buckbrush. Kentucky bluegrass is often associated with patches of western snowberry, and because the adults are weak fliers, the eggs are often deposited in areas with an abundance of Kentucky bluegrass. Kentucky bluegrass, of course, is the ubiquitous lawn grass and has invaded extensive areas of our native prairies.
White grubs can do a lot of damage, in pastures, parks, lawns, and other areas. Larval density in the top few inches of soil may approach 5 or more per square foot. Most of these heavily damaged areas are almost bare of vegetation with most of the roots having been consumed. A person can work their fingers into the ground and roll back the top few inches of this dead sod like a carpet. And as you might expect, skunks, raccoons, and some other animals find the grubs quite tasty, further disturbing the site with their digging.
So, as you travel about, be on the lookout for evidence of these white grub infestations. You may even be able to dig a bit and expose the white grubs, or larvae, of these June beetles.
- Chuck Lura