Preemergence Herbicides for Annual Grassy Weeds

PREEMERGENCE HERBICIDES FOR ANNUAL GRASSY WEEDS

Most turfgrass managers across the state continue to rely on the use of preemergence herbicides to control annual grass weeds.

Newly Seeded Turfgrass (mowed less than 3 times) ~ Siduron should be applied at the time of seeding or prior to the emergence of the weed grasses. A second application may be necessary where weed pressure is heavy.

Established Turf ~ Preemergence herbicides for 2005 include: Benefin (Balan), Bensulide (Betasan, others), Pendimethalin (Pre-M, Pendulum, others), Oxadiazon (Ronstar), Trifluralin + Benefin (Team Pro), Dithiopyr (Dimension), and Prodiamine (Barricade).

Monitor soil temperatures (2-inch depth) to predict annual grassy weed germination. Annual bluegrass germinates in soil temps of 45°F (8ºC), Crabgrass = 50-55°F (10-13ºC), Goosegrass = 60-65°F (15-18ºC), Barnyardgrass = 60-65°F (15-18ºC), and Foxtails = 65°F (18ºC). In Northern Ohio, crabgrass emergence occurs around April 1 to May 1, Central Ohio it occurs around March 15 to April 15, and in Southern Ohio March 1 to April 1.

POSTEMERGENCE HERBICIDES FOR ANNUAL GRASSY WEEDS

After annual grass weeds have established in grass areas, their removal usually necessitates the use of postemergence control products. Those products for 2005 are: Monosodium Acid Methanearsonate (MSMA, Daconate, others), Fenoxaprop p-ethyl (Acclaim Extra), Dithiopyr (Dimension), and Quinclorac (Drive).

Dimension is unique in that it exhibits both premergence & postemergence activity on crabgrass. It is most efficaceous on young crabgrass that is beyong the 1-2 tiller maturity stage. Growth stoppage of crabgrass occurs within 3-5 days after application but actual kill takes 3-5 weeks. It is a good speciality herbicide for use where the critical target date for crabgrass has been missed, a postemergence application is required, but seasonal preemergence control is still necessary.

PERENNIAL GRASS WEED CONTROL

Non-selective, Systemic Control

Products such as Glyphosate (Roundup Pro) and Glufosinate ammonium (Finale) are the two primary non-selectives. Both have systemic activity, are foliar absorbed in 2-4 hours and have no soil residual activity. Glyphosate has also been formulated for more rapid burndown of weeds in the new product called QuickPro, which discolors weeds in 2-3 days. The speed of initial discoloration can also be enhanced with the addition of non-selective contact herbicides such as Scythe or Reward.

Selective Controls

Corsair continues to be available for selective control of Tall Fescue in established Kentucky bluegrass. This product should not be used on perennial ryegrass.

ANNUAL BLUEGRASS (ABG) CONTROL

* Prograss is a postemergence herbicide capable of eliminating ABG from turfgrass areas. Carefully assess the extent of the ABG population before using this product. The best efficacy from Prograss occurs with multiple applications made in the fall.

* Velocity (bispryibac sodium) is an ALS inhibitor labeled in 2005 by Valent for postemergence control of ABG in creeping bentgrass. Velocity will kill ABG in 4-6 weeks depending on rate. At this time, it is labelled for golf course turf (not greens) and sod farms. It is labelled for creeping bentgrass & perennial ryegrass. Research is being done to evaluate effects on Kentucky bluegrass. We will keep field managers abreast of any new developements.

* Certainty (sulfusulfuron) is marketed by Monsanto for selective control of Poa annua & Poa trivialis (roughstalk bluegrass) in creeping bentgrass fairways & tees on warm season turf. It will have a cool season label in 2006.

Authors: John Street, David Gardner, and Deb Holdren