Yellow Nutsedge Management With Postemergence Herbicides: A Three Year Study

Ted Whitwell, David Lowe and Clint Waltz

Department of Horticulture

Introduction

Several herbicides can temporarily suppress yellow nutsedge populations, however, eradication of established nutsedge in turf is nearly impossible. Although some herbicides kill the yellow nutsedge plant tissue, new plants can emerge from the tubers in the soil.

Objective

A three year study was initiated in 1993 to evaluate several postemergence herbicides and herbicide combinations to reduce yellow nutsedge populations in Tifway II bermudagrass.

Procedures

A site infested with yellow nutsedge was selected at the Pee Dee Research and Education Center near Florence, SC. Tifway II bermudagrass was sprigged in May 1993. Plots measured 7 ft X 7 ft and the turf was maintained at a 1 inch mowing height. Treatments included two applications of Image (0.25 lb ai/ A), Manage (0.063 lb ai/ A), MSMA (2.0 lb ai/ A), Basagran (1.0 lb ai/ A), Image + MSMA, Image + Basagran, Manage + MSMA, Manage + Basagran and Manage + Image at each of the mentioned rates. Herbicides were applied with a CO2 backpack sprayer calibrated to deliver 30 gallons/ A with 8004 flat fan nozzles. Treatments were replicated four times using a randomized complete block experimental design.

Treatments were applied as follows:

Herbecides	1993	1994	1995
Pre-Pennant	(none)	May 5	May 2
1st Post Application	July 7	August 2	July 11
2nd Post Application	October 1	September 21	August 31

Yellow nutsedge shoot control was visually evaluated on a scale of 0 to 100% with 0 being no control and 100% complete shoot control. Bermudagrass injury was also visually rated on a scale of 0 to 100% with 0 being no visual injury and 100% complete injury. Tubers were harvested by taking soil cores from each plot, washing the soil and counting the tubers on Dec. 13, 1993; Dec. 10, 1994; and Dec. 21, 1995.

Results and Discussion

Data (Figures 1 and 2) indicate that only Manage + Basagran provided greater than 80% shoot suppression in 1993. In 1994, all treatments but Basagran provided greater than 88% control. In 1995, Basagran provided the least control (59%), followed by Manage (76%) and MSMA (76%). The remaining treatments effectively reduced yellow nutsedge greater than 88%.

The results from tuber counts indicate a reduction in tuber numbers throughout the three year study with only Image + MSMA (from 22 to 1.5 tubers) versus the untreated (from 24 to 4). No other treatments significantly reduced tuber populations.

Minimal turf injury was observed with Image + MSMA, but symptoms were only noticed at two weeks after application.