species of grubworms typically have one generation per year except the
black turfgrass Ataenius may have two per year. Most species live
through the winter in the thatch or soil as larvae in the third instar
grubworm stage. An exception is the Black Turfgrass Ataenius, which
lives through the winter as an adult beetle.
Over-wintering grubworms will move up to feed in the spring and then
move down into the soil to pupate. Adult beetles emerge, mate and lay
eggs. First instar grubworms hatch and begin feeding before the molting
process begins. The seasonal timing of the complex metamorphosis life
cycle varies with each species.
The larvae white grubworm live below the soil surface and feed on the
roots of the turfgrass. Turf damage consists of wilted, dying or dead
patches of turf. Damage to the turf can also occur from birds, skunks
and moles digging for grubworms.
Adult beetles are commonly seen in flight around lights in the evening.
Signs of predator damage digging for grubworms is a valid signal of
larvae presence. Grubworm damage severs the root structure, allowing one
to easily pull up or roll back dead sod. Doing this often exposes
grubworms curled up in a C-position. The various species of grubworms
can be identified by the pattern of spines on the raster. Their raster
is the underside of the tip of their abdomen, which is at the end of the
Generally population levels of 5 to 10 grubs per square foot in poorly
irrigated turf or 15 to 20 grubs per square foot in properly irrigated
lawns will need control measures to minimize damage. Insecticides are
most effective when the larvae have just hatched and are their first
instar. The more mature the grub the more difficult it is to control. It
is very important to water the insecticide treatment down into the soil.
Contact us if these bugs are causing you a problem, and discuss which
insecticides would be most effective for controlling these lawn pests.