SportsTurf provides current, practical and technical content on issues relevant to sports turf managers, including facilities managers. Most readers are athletic field managers from the professional level through parks and recreation, universities.
Issue link: https://read.dmtmag.com/i/560546
50 SportsTurf | September 2015 www.sportsturfonline.com It was late when I thought about put- ting out a pre-emergence herbicide so I thought I would just roll the dice and see what came up on our high school fields. We now have lots of crabgrass in our bermudagrass. Until early July it did not look so bad. The last 2 or 3 weeks it has grown like crazy. So, what can I safely use this late in the year? Crabby in NC O h, the feared and dreaded crab- grass. It is an annual grass that is fairly easy to control with pre-emergence herbicides even though it may require two applications for season-long control. That is worth mentioning since it is easy to forget it's a long time between February (first pre- emergence application) and that second flush of crabgrass that often occurs in mid to late-summer. Even with pre-emergence control, post emergence herbicides may need to be used to remove crabgrass that either escaped the preemergence applica- tion or has come up after the break down of the preemergence product. So, you have crabgrass and it is late summer. Let's review some post-control options. One option is to do nothing. Crabgrass does not like cool weather. Once the summer temperatures begin to drop, crabgrass growth drops off much quicker than the bermudagrass. So, if your infesta- tion is tolerable, then doing nothing may work. If the infestation is widespread (as your question suggests) or your threshold tolerance level is low, then a postemergence herbicide should be considered. There is actually a big advantage to using postemergence products on crabgrass rather than preemergence control. With post applications you are targeting a known weed and treating only the areas that need to be treated. This is the foundation of a good IPM program. So, areas that do not have crabgrass do not need to be treated. If your outbreak is fairly localized this can really be a cost-effective way to control the weed. Of course if the entire field has crabgrass, then this will likely be a more expensive way to target this plant. Crabgrass can also be very unsightly since compared to bermudagrass it has a lighter green color, coarser leaf tex- ture, and a more rapid growth. For many years the go-to product for grassy weed control was the herbicide MSMA. This was an effective product with a low-cost. Currently EPA is con- sidering what to do with MSMA and its status has been a moving target the last couple of years. In 2009, the MSMA label use on athletic fields, parks, and residential lawns was cancelled. The only turf areas that remained on the new label were sod farms, golf courses, and highway right-of-ways. These areas also had various use limitations. If you purchased MSMA by December 31, 2010 with an older "all uses" label then you can continue using as per the label until the supply is exhausted. Even if you have some MSMA, you may not want to use it for crabgrass control. To me, it would be much more valuable to use the MSMA for spot spraying harder to control grasses than on crabgrass. Today there are other herbicides have more effective active ingredients specifically for crabgrass. The suggested active ingredient for postemergence crabgrass control is quinclorac. Currently, the best known product with quinclorac is labeled as Drive XLR8. This newer formulation is a liquid and a bit faster acting than the older dry formulation labeled just as Drive (without XLR8 suffix). The active ingredient is also available as a generic product in the dry formulation. This formulation can also be found mixed with other herbicide products and sold as a combination product under various trade names. Quinclorac is very effective on not only immature crabgrass, but also is effec- tive on very mature crabgrass such as that commonly found in late summer. In addition to being effective on (large and smooth) crabgrass, it also has good activ- ity on some broadleaf weeds such as black medic, white clover, and common dande- lion. The active ingredient quinclorac can also be safely applied to turfgrass other than bermudagrass. If you need greater broadleaf weed control or sedge control one of the com- bination products may be beneficial. If not then a straight quinclorac with the addition of a methylated seed oil (MSO) or a crop soil concentrate is sufficient for great crabgrass control. Application to weeds under stress will result in poorer control. So, apply about 24 hours after a rain or irrigation if drought conditions exist. Check the label for limitations and application directions. ■ ST OVERTAKEN WITH CRABBINESS Q&A with Dr. Grady Miller Questions? Send them to Grady Miller at North Carolina State University, Box 7620, Raleigh, NC 27695-7620, or email grady_miller@ncsu.edu Or, send your question to Pamela Sherratt at 202 Kottman Hall, 2001 Coffey Road, Columbus, OH 43210 or sherratt.1@osu.edu Professor, North Carolina State University So, areas that do not have crabgrass do not need to be treated. If your outbreak is fairly localized this can really be a cost- effective way to control the weed. Of course if the entire field has crab - grass, then this will likely be a more expensive way to target this plant.