Crabgrass Control With Preemergence Herbicide Combinations

Ted Whitwell and Clint Waltz

Department of Horticulture, Clemson University

Introduction

Crabgrass is a pernicious weed in turfgrass that has undesirable color and texture and is very competitive. One goal of a new preemergence herbicide product is to extend the length of crabgrass control in turfgrass. Sulfentrazone herbicide (which may be sold as Sledge) is being developed by FMC for preemergence and postemergence weed control in warm and cool season turfgrass.

Objective

Our experiments evaluated sulfentrazone alone and in combination with standard preemergence herbicides for the duration of crabgrass control in a bermudagrass fairway.

Materials and Methods

Two studies were established in a mixed common and Tifway bermudagrass rough at Boscobel Golf Course near Pendleton, SC. Plots were 3.3 ft X 5.0 ft and treatments were replicated four times using a randomized complete block experimental design. The entire plot area was sprayed with Reward (a non-selective, non-residual herbicide) at 1.5 lbs ai/A to remove all winter annuals. Initial preemergence herbicides treatments were applied on March 28, 1995 and the predetermined plots received a sequential herbicide application on May 31, 1995. All sprayable treatments were applied with a CO2 back pack sprayer delivering 90 gpa and the granular treatments were applied using a hand-held shaker can.

Visual crabgrass control ratings were taken four times during the summer on a scale of 0 to 100 with 0 = no control and 100 = complete control. Data were analyzed by ANOVA and means were compared using Least Significant Differences at P = 0.05. Bermudagrass injury was also visually rated.

Results and Discussion

All Surflan and Pendulum sequential treatments (except Surflan 1+1 lb ai /A) provided greater than 81% crabgrass control (Table 1) by 136 days after the initial treatment (DAIT). The highest rate of Dimension at 0.5 lb ai/A applied once also controlled crabgrass greater than 84% by 136 DAIT. Sulfentrazone alone and in combination with Dimension did not provide comparable season long control. The highest rate of sulfentrazone with Dimension gave 77% crabgrass control by 136 DAIT.

The results of a second study evaluating sulfentrazone combinations with Pendulum and Barricade are found in Table 2. Crabgrass control from the highest rate of Pendulum alone was 81% at 113 days after initial treatment. No other treatment provided better than 80 % control at 113 DAIT. Crabgrass control at 136 DAIT was less than 69% for all treatments. Sulfentrazone alone or in combination with Barricade or Pendulum did not improve the length of crabgrass control with the highest rating of 71% control at 113 DAIT.

Observations on bermudagrass injury at every rating period for both studies indicated no observable effects from these herbicides on bermudagrass growth and development.