TURF TIPS Dallisgrass Control…
Things Are Looking Up
By Dr. Scott McElroy, Assistant Professor of Turfgrass Weed Science, and Greg Breeden, Extension Assistant for Turfgrass and Forage Weed Science, University of Tennessee
W
ithout a doubt, dallisgrass (Paspalum dilatatum) is the most difficult-to-control weed in turfgrass systems in the state of Tennessee. This vigorous perennial develops a strong root system, thus requiring multiple applications of all potential control measures. Even a non-selective herbicide such as glyphosate (Roundup and many other formulations) requires multiple applications for complete control. Also, variation in dallisgrass control is often observed from site to site, typically depending on the age of the stand. The older the stand, the more difficult dallisgrass is to control.
Selective Control in Bermudagrass Turf Traditionally, herbicides such as MSMA (many formulations) and Sencor (metribuzin) have been utilized in combination, with repeat applications every 7-10 days being required for complete control. New herbicides such as Revolver (foramsulfuron) and Monument (trifloxysulfuron) have potential for use in a dallisgrass management plan. However, both herbicides are still being evaluated for specific rates and timings to achieve adequate control. Below are four management options for dallisgrass control in bermudagrass turf.
Management Option #1 — MSMA Alone Apply MSMA (6 lb. ai/gal.) at a rate of 2 lb. ai/ acre (2.67 pt./acre for a 6 lb. ai/ gal. product) every 7 to 10 days for a 30
maximum of 4 applications in one season. MSMA has an 8 lb. ai/acre maximum yearly application limit. Regrowth will likely occur, so a second year of applications may be required. Always check your formulation of MSMA. Some MSMA formulations contain surfactant, and some do not. If the formulation does not contain surfactant, add approximately 1 fluid ounce of surfactant per gallon of spray solution.
Management Option #2 — MSMA plus Sencor Apply MSMA (2 lb. ai/a) plus Sencor (0.5 lb. ai/a, 0.67 lb. product/a) every 10 to 14 days for three applications. If regrowth occurs, follow up — 14 days after the last application — with an application of MSMA alone. Applying Sencor at intervals of less 10 days could potentially injure bermudagrass.
Management Option #3 — Revolver or Monument The new sulfonylurea herbicide Revolver (foramsulfuron) seems to have potential use in controlling dallisgrass. However, spotspraying of Revolver seems to be more effective than broadcast applications. The Revolver herbicide label has a special provision for spot-spraying that allows for the use of 1 fl. oz./gallon of spray solution. For dallisgrass control using Revolver, the following protocol seems to work best. Apply MSMA at 2 lb. ai/acre followed by Revolver as a spot spray at 1 fl. oz./gallon of spray solution. Up to 80% control of dallisgrass has been
TENNESSEE TURFGRASS DECEMBER/JANUARY 2005
observed with this combination, and it has the potential to get dallisgrass control down to 2-3 applications, which is better than has currently been achieved with MSMA or MSMA + Sencor. Spot-spraying can be difficult to achieve on dallisgrass that has taken over large areas. This management option may be easier to attempt when dallisgrass is in distinct clumps of a turfgrass area and not when it is basically a solid blanket over an area.
Management Option #4 — Renovation Sometimes the best option is to simply start all over. Any many cases, if you are dealing with dallisgrass plants that are greater than one foot in diameter, it may take two years of selective herbicide applications to completely control the dallisgrass. In such a situation, the amount of bermudagrass that will be available to occupy the desiccated area will most likely be limited, due to the suppression from the dallisgrass. In other words, there may not be any bermudagrass to take over and fill in the area once the dallisgrass is gone.
Email TTA at: tnturfgrassassn@aol.com
Seedhead of dallisgrass