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.
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www.stma.org bicides are absorbed by germinating weed seedlings in the soil, so moving them into the rootzone is critical. Failure to irrigate after application can also lead to material being lost due to volatilization. On fields without irrigation, try to time PRE herbicide applications around a period of rainfall. #3- Split Applications: Split (also referred to as "sequential") application programs of PRE herbicides tend to provide more consistent control of summer annual weeds throughout a grow- ing season, particularly in southern climates. These programs typically apply the total amount of active ingredient for the sea- son in two equal rate applications spaced 8 to 10 weeks apart. A single herbicide application in spring for PRE control of crab- grass will slowly be broken down by soil microbial activity over the course of a summer often leading to crabgrass breakthrough by fall. Split application programs delivering active ingredient two times throughout a season tend to provide a longer period of control. Additionally, split application programs will control species germinating later in the year than crabgrass (e.g., gooseg- rass, etc.). NO EFFECTS ON TRAFFIC TOLERANCE Research has been conducted at the University of Tennessee Center for Athletic Field Safety (Knoxville, TN) evaluating the ef- fects of four preemergence herbicides on Tifway hybrid bermuda- grass traffic tolerance and recovery. Over the course of a 2-year study, no differences in smooth crabgrass control were detected among herbicide treatments after being subjected to athletic field traffic in spring; control measured 95 to 99% by 5 months after application. Additionally, these PRE herbicide applications for smooth crabgrass control had no effect on Tifway hybrid bermuda- grass traffic tolerance to spring traffic. Follow-up research at the University of Tennessee Center for Athletic Field Safety investigated the effects of PRE herbicide applications in spring on hybrid bermudagrass tolerance to traf- fic during the fall of the year. Similar to the initial study, PRE herbicide applications for summer annual weed control in spring had no effect on hybrid bermudagrass traffic tolerance in fall (Figure 2). CONCLUSIONS Numerous PRE herbicides are available for controlling an- nual grassy weeds on athletic fields. Always refer to the prod- uct label for specific information on proper use, tank-mixing compatibility and turfgrass tolerance. Mention of trade names or commercial products in this publication is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the University of Ten- nessee Institute of Agriculture. For more information on turf- grass weed control, visit the University of Tennessee's turfgrass weed science website at www.tennesseeturfgrass weeds.org. J.T. Brosnan, G.K. Breeden, J.C. Sorochan, and A.W. Thoms University of Tennessee