If you want to panic the homeowner of a well-manicured
lawn, just yell, “Grubs!” White grubs are the most destructive
turf insect pest in Illinois. However, not all turf areas will get grubs,
and the extent of grub damage varies from year to year.
White grubs, which represent the larval stage of
beetles, are creamy-white in color, with a C-shaped body, brown head, and
short legs. The most common grub species are the annual white grubs that
become adult Southern and Northern masked chafer beetles and Japanese
beetles.
Grubs feed on turfgrass roots and other organic matter
in the soil. The damage initially appears as brown areas of the lawn,
similar to the look of drought stress. Continued feeding will cause the
turf to die in irregular patches. This turf can often be rolled back like a
loose carpet.
So do you need to treat your lawn for grubs?
Egg-laying beetles are attracted to well-watered or moist areas of
turfgrass that get full sun. Those of us who didn’t water our lawns
are less likely to have a grub problem.
If you have an irrigated lawn, where you know you
should have a grub problem, July is generally the time to apply an
insecticide. Application of imidacloprid (one brand name is Merit) or
halofenozide (GrubEx) in July to irrigated turf should provide control.
These two insecticides may take as long as three weeks to kill grubs but
last for months in the soil. They are most effective on small, newly
hatched grubs.
If you have not watered your lawn this year, wait to
apply an insecticide until after grubs emerge. In early August, scout for
grubs by sampling square-foot areas around your lawn. Cut through the turf
with a heavy knife on three sides of a square, then peel back the turf.
Grubs will show up in or just below the turf’s root zone. If the soil
is dry, the grubs may be 2 to 4 inches deeper. Check for these deeper grubs
by tilling up the soil with a knife.
A well-managed lawn can withstand a number of feeding
grubs without suffering great damage. Typically a population of 10 to 12
grubs per square foot causes obvious turf damage. Eight to 10 grubs per
square foot may cause injury in heavily used turf. If control is warranted,
apply trichlorfon (Dylox). Grubs must be present when Dylox is applied to
be affected by it. Only treat in and around affected areas.
Once you’ve applied a granular insecticide, you
should apply at least a half-inch of water to move the insecticide into the
root zone, where the grubs will come into contact with it. Before applying
any chemical, read and follow all label directions.
For more information and to view a photo of an annual
white grub, visit the grub page on the University of Illinois Extension Web
site, www.urbanext.uiuc.edu/turf/whitegrub.html.
U of I Extension entomology specialist Phil Nixon
provided information for this article.
Flowers at the fair
Next week, as you make your way through the maze of
tents, livestock buildings, and food stands at the fairgrounds, take note
of the beautiful flowers.
Bright red and orange cannas, yellow marigolds, blue
salvia, and white petunias are just a few of the 150 different kinds of
flowers on display. Flowerbeds — 226 in all — are tucked
in every corner. This year, the flower displays feature for the first time
artfully displayed antique farm equipment.
Look up and see one of the 175 hanging baskets, some
of which contain trailing pink and purple petunias. Along the avenues are
65 concrete planters, some bursting with tall orange cannas and cascading
black sweet-potato vines.
Inmates at the Lincoln Correctional Center started the
150,000 flowers from seed in March. Each day during the fair, a dozen Logan
Correctional Center inmates care for the flowers under the watchful eyes of
corrections officers.
If you need help identifying flowers or have any
gardening questions, see a master gardener at the University of Illinois
Sangamon-Menard Unit, in Building No. 30, along Eighth Street.
They’ll be there each day, 8:30 a.m.-4:30 p.m
This article appears in Aug 4-10, 2005.
