December 1996 - Volume III, Issue 12

Herbicide Research - 1996

David M. Kopec, Extension Turfgrass Specialist

This past summer, I conducted several field trials to evaluate a new compound for herbicide control of purple nutsedge. The compound, from FMC, is named Sulfentrazone. It was applied to purple nutsedge, bermudagrass, tall fescue and perennial ryegrass turf. We applied the product over a range of rates as single applications and in some cases, as split applications thirty days later.

The compound shows activity on purple nutsedge. At the highest rate tested the control was slightly less than that of Halsulfuron (MANAGE) and Imazaquin (IMAGE). Sulfentrazone acted a little slower than MANAGE, but quicker than IMAGE. I have formulated some rate/timing combinations using this product which may enhance the activity and increase the control. Purple nutsedge eventually grows back from essentially all applications of any herbicide. Whatever you use, you must use it repeatedly, till all the nutlets are exhausted.

At the highest rate tested (which was best on the nutsedge), there were slight but noticeable effects on the turfgrasses.

On common bermudagrass, the leaves were marginally twisted or cupped for up to ten days, followed by some lower leaf sheath necrosis. This makes the bottom of the canopy appear "straw like" when you get down on your hands and knees. Also, a slight loss of color occurred, but it was uniform (not blotchy). The turf grew out of these responses nicely. IMAGE turned the common bermudagrass the most "off color."

For tall fescue, the product caused only a slight and uniform color loss, but it did enhance leaf cupping/twisting of the youngest leaves. Even the control (untreated) turf showed some symptoms under summer stress, but it was enhanced by the herbicide.

On the perennial ryegrass, some of the turf became "pock-marked", not from differences in color changes, but more like a "wisping" effect across the turf from slight leaf cupping/twisting. These effects were short lived.

The product never caused leaf tip burn, blotch-type symptoms, random discoloration, or stunting. Some of these responses were subtle to minor. None of these were as obvious as would be MSMA (with surfactant) applied foliar to these grasses during the summer.

We will keep you posted on further research and the fate of this experimental herbicide.

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