Turf - Controlling Crabgrass Breaks

The following is general information on controlling crabgrass breaks in turf.

With the heavy rains and cool weather conditions this spring I’m expecting that a significant number of preemergence herbicide applications will fail. Above average rainfall will result in an increased dissipation of preemergence herbicide out of the crabgrass germination zone while the cool temperatures are prolonging the crabgrass germination cycle. As always, maintaining a dense and healthy turfgrass stand throughout the summer is our first and best line of defense to prevent preemergence crabgrass herbicide failures. However, if summer stresses which thin and weaken the turfgrass stand occur; postemergence herbicides may need to be utilized to control crabgrass that germinates later in the season.

Both Acclaim Extra and Drive herbicides can be used to control crabgrass breaks. However, crabgrass cannot be too large (ideally less than 2 tillers, but no more than 4 tillers). Both herbicides are most effective when applied to young actively growing crabgrass in good soil moisture conditions. Applying either herbicide to sites under drought and/or heat stress may result in reduced control of crabgrass and other summer annual grasses as well as increased potential for turfgrass injury. Weed control with both herbicides is most effective when applied with flat fan nozzles producing a fine spray droplet. I do not recommended the use of flood jets with either herbicide. Both herbicides may be applied in combination with residual preemergence herbicides. However, applying residual herbicides late in the season may interfere with overseeding operations in late summer/fall.

Information adapted from an article from Dr. Steve Hart, Extension Weed Science Specialist, Rutgers University.

Turf - Drive for Postemergence Crabgrass Control

Crabgrass breaks are occurring in landscapes this year due to the previous wet weather. The following is information on using quinclorac (Drive) herbicide for postemergence crabgrass control.

Drive Herbicide

Drive herbicide (quinclorac) is safe on Kentucky bluegrass, perennial ryegrass and tall fescue. Consult the label carefully for use on bentgrasses and fine fescue. Drive can be effective on 2-4 tillered crabgrass but for the most consistent control Drive should be applied to crabgrass prior to two tillers. Drive is also highly active on large multi-tillered crabgrass but only when it has entered its reproductive phase (visable seedheads). Drive will not control goosegrass. Drive is tank-mix compatible with broadleaf weed herbicides. For optimum activity Drive must be applied with methylated seed oil (MSO). Two formulations are available: Drive 75 DF and a new liquid formulation Drive XLR8 1.5 L. In some studies we have observed more consistent crabgrass control with Drive XLR8 compared to Drive 75 DF.

Combination Products: A number of combination products are currently being marketed such as Q4, Quincept, and Onetime, which contain Drive in combination with broadleaf weed herbicides or in the case of Q4 also contain sulfentrazone for suppression of yellow nutsedge. Consult labels carefully to determine if a spray adjuvant is recommended. Also determine the use rate of quinclorac (the active ingredient in Drive) you will be applying. Applying quinclorac at less than 0.75 lbs ai/A and/or without a spray adjuvant such as methylated seed oil may reduce the consistency of crabgrass control especially if the growth stage has exceeded one-tiller.

Information from Dr. Stephen E. Hart, Associate Extension Specialist, Weed Science, Rutgers University

Turf - Know Your Herbicides I

This is the first in a series on knowing the herbicides that are used in professional turf management. The first post is on the material quinclorac.

Information largely from the Drive label. Go to http://www.cdms.net/LDat/ld4BF009.pdf for the full label.

Turf - Late Season Crabgrass

The following is some information on late season crabgrass management.

While normally we do not advise controlling crabgrass this late in the season, with the recent rains and warm weather still, crabgrass escapes are very noticeable, especially in turf areas thinned out by the drought. At this time of year, crabgrass goes to seed very quickly so you may want to consider a late season control to reduce seed production. The two options at this time are Drive and Acclaim Extra. Both can be used on areas to be reseeded to turf-type tall fescue. With expected cooler weather, crabgrass growth will slow down considerably. Note turf areas with crabgrass problems and target these areas for preemergence herbicides next spring. If you choose not to control crabgrass chemically, mow frequently to reduce seed head production. Even with frequent mowing, there will be some seed production as crabgrass will often produce seed heads below the level of the mower blade in September. If grass stands have thinned out due to the drought, you will want to reseed areas now. If crabgrass is left, it will actually provide some protection to new seedings as it will die out with frost.

Gordon Johnson, Extension Agriculture Agent, UD, Kent County