Weed of the Week: Dallisgrass

Dallisgrass. Photo courtesy of Dr. Paul Baumann

Dallisgrass is a warm-season perennial that has grazing potential. Dallisgrass is palatable and has a higher level of nutritive value than bahiagrass and some bermudagrass varieties, and it can retain its nutritive value later into the summer. Dallisgrass, however, produces a lower dry matter yield than some bermudagrass varieties. One concern with dallisgrass is the potential for an “ergot” fungus (Claviceps spp.) to infect seedheads and cause dallisgrass poisoning (also known as dallisgrass staggers). The fungus infects the seedheads typically in late summer or fall. The affected animals show neurological symptoms including trembling of major muscles and head, uncoordinated movements and sometimes displays of aggression. Poisoning can be avoided by removing livestock when seed heads are affected or keeping seed heads mowed.

So how to manage unwanted dallisgrass? 

Dallisgrass seedhead. Photo courtesy of Dr. Paul Baumann

Use of herbicides to control dallisgrass is probably the most common method practiced. Glyphosate (active ingredient in Roundup, etc.) is the only postemergence herbicide option. As with any herbicide application timing is critical along with following label directions. Ideally, dallisgrass needs to be sprayed when plants are less than 6 inches in height in the spring. Unfortunately for bahiagrass growers there are no selective herbicides available for postemergence control of dallisgrass, thus spot treatments of glyphosate are recommended. For rates and any restrictions refer to product labels. In bermudagrass, there is often an opportunity to selectively control dallisgrass with glyphosate at the end of the season.  Often, there is a period in late fall to early winter when bermudagrass becomes dormant while dallisgrass remains green for a short period of time. During this time glyphosate provides fair to good dallisgrass control. Bermudagrass injury varies depending on the stage of dormancy at the time of application. Timing and calibration are important. Once the first frost occurs, bermudagrass should be checked frequently so that the application can be made as soon as it is completely dormant. If glyphosate products with higher concentrations are used, the rate should be adjusted.



Vanessa Corriher-Olson

Professor, Forage Extension Specialist

Soil & Crop Sciences

Texas A&M AgriLife Extension, Overton,TX



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