Dr. Pete's Turf Tips
Peter H. Dernoeden, Ph. D.
Crabgrass, goosegrass, Japanese stiltgrass and yellow foxtail are highly invasive annual grasses that germinate in spring and become objectionable turf competitors in summer. The most effective and economical means of controlling summer annual grasses is via the use of an early spring applied preemergence herbicide. Postemergence control is tough, and success is based mostly on good calibration and timing, good soil moisture, choosing the most suitable herbicide for the turf species grown and the “phase of the moon.” Once numerous tillers (i.e., shoots) and seedheads form, most herbicides become erratic.
The key postemergence summer annual grass weed herbicides include: Acclaim Extra (fenoxaprop-ethyl), Drive XLR8 (quinclorac), MSMA (monosodium methane arsonate), Pylex (topramezone) and Tenacity (mesotrione). Most of these herbicides cannot be used safely and effectively on both cool and warm-season grasses. Creeping bentgrass is highly sensitive, if not intolerant to, the aforementioned herbicides. There are no products labeled for use on bentgrass greens. We will try to succinctly explain differences among herbicides and species tolerance, but The Label must be consulted using any product, especially for the first time. The label is the law and you need to ensure using proper rates and timings, well calibrated equipment, and know the sensitively of their use on different turf species. Subsequent applications may be needed where significant numbers of these annual grasses emerge in the latter part of summer. Generally, herbicides are most effective in early July when newly tillered (i.e., 2-4 shoots) weed grasses are evident and growing above the turf canopy.
Acclaim Extra effectively controls crabgrass, foxtails, goosegrass and Japanese stiltgrass. It is safe to use on most cool-season grasses; however, it must be used with caution on higher cut bentgrass tees and fairways. Acclaim is highly phytotoxic to bermudagrass. It is best used in early summer when plants are in the 2 to 4 tiller stage. Mixing Acclaim with broadleaf herbicides like 2,4-D, MCPP and dicamba antagonizes Acclaim, and little or no annual grass weed control will occur. Acclaim, however, is not antagonized by fluoxypyr (Spotlight) and other broadleaf herbicides stated on the label.
Drive XLR8 effectively controls crabgrass, and it should be mixed with methylated seed oil or other adjuvant listed on the label for best control. Drive also is effective on some tough broadleaf weeds such as clovers, speedwells, wild violet and others. Most cool-season grasses, as well as common bermudagrass and zoysiagrass, are tolerant of Drive; however, some yellowing may occur . Fine leaf fescues and hybrid bermudagrass are less tolerant. Drive may be applied to creeping bentgrass fairways and tees, but it can cause several weeks of objectionable yellowing. Optimum timing for Drive application is before tillering and after crabgrass plants have reached the 5-tiller stage, but before massive numbers of tillers and seedheads appear. Late summer applications often provide a burn-down of crabgrass foliage and will help to reduce seed production and reduce competition.
MSMA no longer is being manufactured; however, existing stocks can be used legally. MSMA’s greatest strength is its ability to control Dallisgrass (and related perennial species). MSMA is mostly used on bermudagrass for annual grass weed control. Bermudagrass is highly tolerant, allowing for higher rates to be used during hot summer periods, but is risky to use in summer on cool-season grasses. 
Pylex has brought much interest given its ability to severely suppress common bermudagrass (aka wiregrass). Pylex is mostly used on Kentucky bluegrass, perennial ryegrass, tall fescue and fine-leaf fescues. Bentgrasses, bermudagrass and zoysiagrass are intolerant at rates used on the aforementioned turfgrasses. Pylex, however, is labelled in bentgrass and bermudagrass tees and fairways at significantly reduced rates for control of certain grasses. Pylex controls all summer annual grass weeds. It’s most exciting attribute is that it can kill multi-tillered goosegrass. It should be mixed with methylated seed oil or other adjuvant noted on the label. When applied alone, it will cause severe bleaching/whitening of the target weed and will induce yellowing in cool-season turf. Mixing Pylex with triclopyr (Turflon Ester) eliminates most of the bleaching and yellowing. The addition of triclopyr also boosts control, while killing some broadleaf weeds. Do NOT mix triclopyr with Pylex for use on bentgrass and other highly sensitive species.
Tenacity is the best herbicide to use when seeding cool-season grass (except bentgrasses). When applied to the seedbed, it controls a multitude of weeds preemergence including crabgrass, foxtails, yellow nutsedge, clovers and other broadleaf weeds. Creeping bentgrass, bermudagrass and zoysiagrass are very sensitive. It is effective in controlling crabgrass, creeping bentgrass, clovers, yellow nutsedge and other weeds postemergence. Tenacity, however, requires at least two and sometimes three applications to be highly effective. Like Pylex, it causes bleaching of targeted weeds and yellowing of turf, but these discoloration issues are greatly minimized by tank-mixing Tenacity with triclopyr.