Andrew Hollman- Glyphosate for Control of Undesirable Grasses in Fine Fescue Mixtures

Introduction

The use of fine fescue species is increasing in turfgrass areas around the state. Whether the area is newly seeded or transitioning from a previous turf, undesirable perennial grasses often invade the newly establishing fine fescues. Although there are a number of selective grass herbicides which are labeled to control certain undesirable grasses in fine fescue, turfgrass managers may not have them on hand, be familiar with their use, or be comfortable with the efficacy of the product. Glyphosate is a common non-selective herbicide which most turf managers have on hand and are familiar with the use of. Glyphosate also readily breaks down in the soil after application and the labeled rate for control of fine fescue is much higher than other annual and perennial grasses. The objective of this study is to examine increasing rates of glyphosate for controlling undesirable grasses while maintaining fine fescue cover.

Materials and Methods

The trial was conducted on an irrigated fine fescue plot seeded with an equal part mixture of Chariot hard fescue, Longfellow 2 Chewings fescue, Cardinal strong creeping red fescue, and Seabreeze GT slender creeping red fescue in the fall of 2011. The plot was mowed at 1.75 inches with the clippings removed. Treatments were applied to 3×5 foot plots with 5 replications per treatment. Eight RoundUp Weathermax (48.8% glyphosate) treatments were applied at 0, 11, 22, 32, 48, 64, 85, and 106 fluid ounces/acre which corresponds to labeled rates for grasses to control (Table 1). Four inch plugs of creeping bentgrass, Kentucky bluegrass, annual bluegrass, tall fescue and perennial ryegrass were inserted into each plot to assess the effectiveness of treatments. Plugs were allowed to grow for 10 days before treatments were applied. Plots were rate for death of the plugs and percent live cover of the fine fescue.

Results

At 6 weeks after treatment fine fescue mixtures had 100, 96.2, 67, 43, 16.4, 3.8, 1.8, and 7.8 percent living ground cover for 0, 11, 22, 32, 48, 64, 85, and 106 fluid ounces/acre rates respectively.

Table 1: Labeled Rates of RoundUp Weathermax for Grass Control