Although all indications are that larval annual
white grubs should be present now in large numbers,
we have yet to find any in central Illinois or in any
other part of the state.
The adult beetles emerged later than usual,
probably because of the cool spring. We normally first
see adults in east central Illinois on the evenings of July
2 or 3, but we did not see them until July 7, almost
one week later. July 18 was the last time that we
saw beetles in central Illinois.
Because the beetles do not feed, they normally
live for only about two weeks. At The Morton
Arboretum in northeastern Illinois, annual white grub adult
flight peaked on July 22, and a few were still present in
the first week of August. In most years, annual white
grub flight is over in northern Illinois near July 25.
Beetle flights ranged from normal in some areas of the
state to above average in many areas, including
When turf is dry and dormant, the adults migrate
to irrigated turf to lay their eggs. Unirrigated
turf throughout most of Illinois was dry and dormant
in July. This should have resulted in large numbers
of eggs being laid in watered turf.
The eggs that the masked chafers or annual
white grub adults lay usually hatch in two to three
weeks. High soil temperatures around 90°F and
above will reduce hatching. However, soil temperatures
have been in the 70s during this time. The resulting
white, C-shaped grubs are easily noticed against dark
soil, even the newly hatched ones, which are
approximately 3/16 inch long. They are present in the
root zone of turf if the soil is damp. Dry soil will cause
the grubs to move downward in the soil column.
With the late flight of the beetles, we do
not anticipate damage to occur until late August
in southern Illinois and until almost mid-September
in northern Illinois. Grub numbers of ten or more
per square foot are likely to cause turf damage.
If raccoons, skunks, or birds feed in the area,
turf damage will occur at much lower numbersthree
to five grubs per square foot. Raccoons peel back
four- to twelve-inch-wide sections of turf to feed on
the grubs. Skunks tear out divots of turf that are three
to six inches in diameter. While a raccoon usually
tears out six or fewer sections of turf in an area, a
skunk usually makes 30 or more holes. Birds pick at the
turf, tearing out the sod in one-inch pieces. Such
feeding causes the affected areas to turn brown from
the removed thatch and sod.
If treatment for grubs is needed at this time,
use faster-acting insecticides such as trichlorfon
(Dylox, Proxol), bendiocarb (Turcam, Intercept), or
isozofos. Triumph is labeled for use only on home lawns,
sod farms, and golf course tees, greens, and
aprons. Diazinon is not labeled for use on golf courses or
sod farms. Grubs treated with diazinon will stop
feeding but will take about three weeks to die.