Keep mowing when the grass or weeds dictate mowing. The rule of
thumb is to remove no more than a third of the leaf blade at any
one time. This means that if your desired mowing height is 2
inches, you should be mowing when the grass gets 3 inches tall.
With recent rains (and a good crabgrass crop) it may be
difficult to keep up with the mowing frequency.
I have had some grub samples brought into the office this
past week. This means that the grubs are active. Grub problems
are normally found first along walks, driveways or patios.
Japanese beetle numbers will greatly increase the number of
lawns treated. Treatments are mostly imidacloprid, trichlorfon,
halofenozide or carbaryl insecticides. Many of these are
pre-mixed with fertilizer. The insecticide must get to where the
grubs are, so make sure to water the liquid formulations in as
soon as they are applied. Granular formulations give you some
time to wait on rain.
The other brown grass problem is either disease or heat
stress on chiefly Kentucky bluegrass lawns. This tends to be in
open sun, where there are traffic areas, where water may have
stood with heavy rains and other similar stress areas. In any
case, these areas appear dead. They may have just had the top
portions die back, and further growth may occur from the root or
crown areas when some cooler temperatures return. If diseases
were present, it won't do any good to spray them. If areas don't
start greening up by Sept. 10, see the section below on seeding.
Seeding of grass should be accomplished by Sept. 10. This is
a tried and true date, but the end of the world won't come about
if you are a week later. The goal is to give the seed enough
time to germinate and become established before bad weather
arrives. Seed at the rate of 4 pounds of seed per 1,000 square
feet on bare spots, or half that rate on overseedings.
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If you have a compacted yard or a deep thatch layer, now is also
an ideal time to dethatch or aerate. Thatch layers should not be
over 1/2-inch deep for optimum growing conditions. When aerating,
make sure you use a core-type aerator.
Fall fertilization is also a good practice. If you haven't
fertilized in the last month, consider applying a fertilizer
treatment now. Use about 8 pounds of 13-13-13 fertilizer per 1,000
square feet of lawn. Try to avoid the high nitrogen fertilizers this
late in the year. It's hard enough to keep up with the mowing as it
is, and nitrogen promotes top growth. The even analysis fertilizers
will also promote root growth, which is what we want going into the
late fall and winter.
Crabgrass and other annual grass weeds can be seen about
everywhere. They will die with the first frost, so treatment is not
available or recommended in the fall. Make a note of where these
grasses are for possible treatment next spring. An overseeding to
thicken up the grasses you want in these areas may help crowd out
Last, but not least, is broadleaf weed control. Fall is a
particularly good time to treat problem perennial weeds since they
are sending food down to the roots to overwinter. A spray about the
third or fourth week of September (making sure to use the
appropriate product) can do a world of good on the perennial weeds.
Remember to be very careful with herbicides around perennial plants
since they are also getting ready to overwinter. By waiting until
late September, you will minimize damage to neighboring gardens and
Fulton, unit leader,
University of Illinois Extension,
Logan County Unit]