Quantcast Controlling Broadleaf Weeds

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AFM 91-19 / TM 5-629 / NAVFAC MO-314
24 May 1989
seeds germinate in spring and summer later than
(9) Tall fescue, timothy, orchardgrass, and
crabgrass. Preemergence treatments for crab
other perennial bunch grasses give a clumpy
grass control should be reinforced with a second
appearance to fine turf because of their rapid
application at 1/3 to 1/2 the initial rate in 4 to 5
growth. If only a few clumps occur, they can be
weeks to provide better goosegrass control. Most
removed by cutting under them shallowly with a
herbicides give variable results, but oxadiazon
spade, or the bunch grasses can be spot sprayed
tends to be more reliable than the others. Some-
with glyphosate. The bare spots then can be
times it may be best to till the fumigate the soil,
resodded, or filled with topsoil and seeded.
correct the causes of the goosegrass problem,
(10) Dallisgrass and some other Paspalum
and reseed or sod in the fall to allow time for a
species can be selectively controlled by repeated
dense turf to develop before the next spring.
postemergence spraying with DSMA and other
(6) Annual bluegrass tends to be a major
methanearsonate herbicides at the highest rates
problem in closely mowed turf, such as putting
recommended on the label. Multiple methanear-
greens, in thin turf, and along turf borders. It is
sonate treatments, however, may severely dam-
a cool-season species whose seeds can germinate
age cool-season turf grasses such as Kentucky
throughout the year, except in the deep South.
Most preemergence herbicides used in cool-
d. Controlling Broadleaf Weeds. Recom-
season grasses give only partial control. Good
mended herbicides are shown in attachment 11.
turf-management practices, including infrequent
(1) Broadleaf weed-control herbicides are
irrigation and high mowing, may limit infesta-
usually applied as postemergence treatments to
the foliage and stems of actively growing weeds.
(7) Annual bluegrass can be well controlled
Most should be applied in early fall, to allow
in bermudagrass in the southeastern states by
grass to fill the spaces left by dead weeds, or in
using metribuzin or pronamide as either a pree-
the spring.
mergence or postemergence treatment. Do not
(2) Most broadleaf weeds can be controlled
overseed treated areas for 90 days after applica-
by using one of the commercially available
tion of pronamide. Pronamide will kill most
products containing 2,4-D in combination with
cool-season turf species. Ethofumesate will
dicamba, mecoprop, dichlorprop, triclopyr, or
safely control annual bluegrass in perennial rye-
chlorsulfuron. In newly seeded turf, bromoxynil
grass and dormant bermudagrass, but will injure
(0.38 and 0.5 lb/a) will control many seedling
other turf grass species.
broadleaf weeds. For weeds not controlled by
these herbicides you may consult your local
(8) Bermudagrass, quackgrass, zoysiagrass,
County Agricultural Extension Service for spe-
kikuyugrass nimblewill, and other perennial
cific recommendations. Do not mow turf for at
grasses that spread by horizontal stems, either
least 3 days before application so that there will
below or above ground, often occur as weeds in
be maximum weed foliage to receive the herbi-
cool-season turf grasses. They can be controlled
cide spray. Do not mow or water the turf for at
by the methods of renovating turf that are
least 2 days after treatment.
discussed in section B. Glyphosate (3 to 6
(3) When a granular 2,4-D or similar herbi-
tablespoons per gal water) is a good nonselective
cide for broadleaf weed control is used, be sure
foliage spray for spot treatments. Such spread-
to follow the instructions on the label. It is
ing perennial grasses often have dormant buds at
generally recommended that such formulations
the joints of the spreading stems that may not
be applied either when the weed leaves are moist
be killed by a single treatment of herbicide.
with dew in the early morning or just after the
When practical, a second application 1 to 2
lawn is watered. The herbicide granules retained
months later increases the chance of eradicating
in water droplets on the leaves are readily
these species. Close observation for any live
plants should continue for many months or
(4) A high percentage of lawn weeds are
years after treatment. Because glyphosate is
controlled by 2,4-D, but there are some com-
effective only when applied to leaves, an abun-
mon weeds it does not control. Weeds that are
dance of foliage on the weed grasses in necessary
not well controlled by 2,4-D, but that may be
at the time of application. Treated spots can be
controlled by dicamba, include knotweed, red
seeded, sprigged, or sodded soon after treat-
sorrel, white clover, henbit, chickweeds, black
ment. Any reinfestation should be spot-treated
medic, ground ivy, yellow woodsorrell, wild
as soon as observed.


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