|
 “Crabgrass is an abundant seed producer, as
evidenced by the large seedling populations easily found now in
Central Illinois,” says University of Illinois Extension Specialist
Michelle Wiesbrook. “By now, many spring-applied crabgrass
preventers have degraded and are likely no longer doing their
intended job.”
As a weed species, crab grass is opportunistic. Both large
crabgrass, Digitaria sanguinalis, and smooth crabgrass, D. ischaemum,
are commonly found in the Midwest. Its stems typically grow
prostrate, forming a mat. Crabgrass can be found in most warm,
moist, fertile lawns in sunny areas where turf is thin or mowed too
short.
“Crabgrass likes ‘hot spots’ next to the driveway or sidewalk, since
it tolerates hot, dry, compacted soils,” Wiesbrook says. “From
there, the weed may spread aggressively to crowd out desirable
grasses.”
Prevention
Preventing crabgrass is easier than treating it when its grown,
Wiesbrook says. A dense, healthy turf is more resistant to
crabgrass, so mow grass tall and water deeply. In landscape beds,
mulch and other weed barriers can be used to prevent weed
germination.
Remove existing plants by hand using proper tools to ensure complete
removal of the roots.
Preventative herbicide may be applied in spring
before germination, and follow label directions for application. [to top of second
column] |
Crabgrass is best prevented in early spring by using
a pre-emergent herbicide prior to seed germination once soil
temperatures stabilize at 55°F. Irrigation or rainfall is then
needed for activation.
"Look for herbicides with these active ingredients for cool season
turfgrass: benefin + trifuralin, dithiopyr, oxadiazon, pendimethalin,
prodiamine, quinclorac, siduron, and sulfentrazone," Wiesbrook says.
Treatment
For crabgrass that has emerged, make two applications of graminicide
two weeks apart, Wiesbrook says. Options include fenoxaprop,
fluazifop, sethoxydim, and clethodim. Cool season turfgrass options
include bispyribac-sodium, fenoxaprop, mesotrione, quinclorac, and
topramezone.
Smaller plants are more easily controlled. Injury can occur to turf
if applications are made when temperatures are greater than 85°F, so
be willing to accept some injury or wait for cooler days to apply.
Misidentification can lead to improper control approaches that waste
time and money, Wiesbrook cautions. For help identifying grasses,
check out the pocket-sized guide Identifying Turf and Weedy Grasses
of the Northern United States available at pubsplus.illinois.edu.
Illinois Extension provides additional information in its online
Home, Yard, and Garden newsletter.
[Michelle Wiesbrook, Extension
Specialist, University of Illinois] |
