WHY DO I HAVE CRABGRASS NOW?
BY GEORGE EDGAR
“Why do I
have crabgrass now in August when I put crabgrass preventer on in
March?” There are three possible reasons why:
Pre-emergent products must be watered in thoroughly (at least ½ inch)
within 24 hours to be effective.
If a pre-emergent was put on in March, it was applied about a month too
early and by the 4th of July was worn out and the crabgrass
The pre-emergent crabgrass preventer you used may have been put on at
the right time but was worn out by the middle of July. Some products
keep working longer than others. Products with Balan or Benefin (Team)
as the active ingredient, has a residual or lasts only about 60 days.
Pendimethalin (Scotts Halts, many box and hardware store brands, and
Miracle Gro Pre-emergent) also lasts about 60 days. Barricade (Earl May
Crabgrass Preventer with Barricade) and Dimension (Crab & Spurge
Preventer with Dimension by Monterey) lasts about 90 days.
year, do not apply a pre-emergent weed herbicide until mid to late April
because crabgrass will not germinate until about the 1st of
May in Lincoln and a few days later in Central Nebraska. Then use a
product with a long residual. To make sure you have season long control,
put on a second application the first couple of weeks in June. This will
give you control for the whole summer. This second application in June
will also help to control spurge and foxtail as they do not germinate
until mid-June. There is a liquid pre-emergent without fertilizer
(Crab & Spurge Preventer with Dimension by Monterey) and a granular
pre-emergent without fertilizer (Crabgrass Control with Team by
Fortify). You can use one of these for the second application if you
don’t want to add more fertilizer in mid-June and thus risk burning
your bluegrass or fescue grass.
garden centers also carry a pre-emergent weed herbicide that is labeled
for use in the vegetable and flower garden. Most of these, such as
Preen, contain trifluralin (Treflan). It has a short residual so must be
applied more than once during the growing season.
is an annual grass that will die with the first hard frost. You can try
and kill it now but it is very mature, so hard to kill at this time. The
most effective product to use to kill crabgrass is Quinclorac. This
product only became available to homeowners in the last couple years. It
is sold under the trade name of Drive and Earl May Total Weed Control
(Ready-To-Spray). The RTS or Ready-To-Spray bottle from Earl May also
contains 2, 4-D and Dicamba and covers 6,600 square feet. The Earl May
Total Weed Control in the Ready-To-Use (RTU) bottle and in the
concentrate does not contain Quinclorac this year so get the right
acid methanearsonate (MSMA) will also kill crabgrass but is not as
effective as Quinclorac. MSMA will take two to three applications 7 to
10 days apart. Even if you do kill it, the crabgrass has already gone to
seed. So plan on seeing it next year.
other broadleaf weeds in your lawn like dandelions and hard to kill
weeds such as bindweed, clover, ground ivy (creeping charlie),
chickweed, black medic, henbit, dandelion, and poison ivy, wild violets,
and white clover, a good time to go after them is after the first light
frost in the fall and before a hard freeze.
the lawn, I like liquid weed killers that you spray on with a spritz
bottle or a small pump-up sprayer rather than the granular kind of
herbicide such as a “weed and feed” you apply with a spreader.
The granules need to stick to the blades of grass to be effective
and usually they don’t stick very well. Another advantage of liquid
weed control is you can spot treat the weeds without putting the
herbicide on the whole yard and areas where it is not needed.
This is better for the environment. Be careful with a hose end
sprayer that you do not put chemicals in areas that have no weeds, or
more on the lawn than you really need.
in the ready-to-spray bottle will control bindweed, clover, ground ivy
(creeping charlie), chickweed, black medic, henbit, dandelion, poison
ivy, wild violets, and white clover, with one application. If you use a
liquid weed control that contains 2-4-D, MCPP, and Dicamba it will take
two to three applications, 7 to 10 days apart to get a good kill This is
sold under the brand names of Trimec, Earl May Lawn Weed Killer, Ortho
Weed-B-Gone II, and Earl May Super Brush and Weed Killer. Triclopyr (Ortho Weed-B-Gone Chickweed, Clover and Oxalis
Killer for Lawns) is a good weed killer but will also take 2 to 3
applications. None of the products mentioned above will hurt your grass
if applied at the proper rate and according to label directions. Don’t
water for 24 hours after application so the chemicals stay on the leaf
and do their work. These weed killers are systemic which means when
sprayed on the leaf, the chemical will be taken down to the roots. Be
sure and read the label and follow the manufacturers recommendations.
weeds and many plants have a waxy leaf and the use of a sticker-spreader
helps the chemical stick to the leaf and thus makes it more effective.
Use a “sticker-spreader” such as “Turbo” at the rate of two
tablespoons per gallon of water, or Acme Sticker-Spreader following the
label instructions. A “sticker-spreader” will help any liquid spray
stick to the leaf of the weed or plant. Use it with a fungicide for
black spot on roses and for tomato blight, or with insect killers such
as Eight, Malathion, Isotox, or Sevin, as well as with a weed killer.
the late fall, after the first light frost, the plants start taking
nutrients down into their roots for the winter and they take the
chemical down with them. In the spring and summer the plants are growing
vigorously and pumping lots of nutrients up into the foliage so is
harder to get the chemical down to the roots. So late fall is a good
time to go after those weeds in the lawn, as well as in the vegetable
garden, and in the flower bed. Digging weeds or killing weeds with
chemicals in the fall will reduce your work load for next spring and
the weeds do over winter, apply a weed killer early in the spring before
planting. You can replant 7 to 10 days after using Glysophate (Kleen-up
or Round-up) but must wait 4 to 6 weeks before planting after use of
Quinclorac, Trimec, or Triclopyr weed killers.
One final tip:
Never apply a liquid or a granular weed killer or fertilizer to a
drought stressed lawn, or when the temperature is over 90 degrees F. or
when the wind is blowing over 5 to 10 miles per hour. An application to
dry soil and/or when the temp is over 90 degrees F. may burn the grass
and cause more stress. Water
thoroughly at least one day before application.