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Tropical Signalgrass

Tropical Signalgrass


Urochloa subquadripara , more commonly known as tropical signalgrass (TSG), is one of the most troublesome weeds in warm-season turfgrass. The challenge with TSG is that with the loss of MSMA, TSG has exploded and there are limited control options that do as well at managing TSG as older chemistries.


Germination occurs when soil temperatures reach 77°F. Seed germination requires soil moisture and a pH of 5 to 6. In colder climates TSG will die back with frost. However, in states that are warm year-round and frost does not occur, TSG will continue to grow and can form large patches. Extended droughts will reduce the infestation of TSG.


Tropical signalgrass is a perennial grassy weed with trailing, creeping stems that root at nodes. [It has flat, hairy blades and sheaths and a ligule with a short fringe of hairs.] It is propagated by seed and stolons. Leaf blades are flat and up to 1/2” wide. Leaves can be 3/4” in length. [Both the leaf blade and sheath are hairy. The ligule has a tropical signalgrass short fringe of hairs.] Flowering branches produce 2 to 7 branches in the raceme of the seedhead.



Integrated management is necessary for TSG control. Maintaining a healthy, lush turf that can outcompete weeds can go a long way in managing not only TSG, but other pests. Scouting and mapping infestations can help identify areas that need extra attention for reducing the spread of TSG. Cleaning equipment or mowing infested areas last can help prevent the spread of stolons and nodes that can be spread by equipment.


Always tank mix or rotate herbicides modes of action. Not only will this help reduce the risk of resistance, but tank mix combinations are better at managing TSG than standalone herbicides. Xonerate ® 2SC Herbicide is labeled for managing TSG. Xonerate 2SC Herbicide demonstrates root and foliar absorption. After application, TSG initially becomes chlorotic and/or stunted, followed by leaf necrosis beginning from the leaf margin and progressing through the plant. Fall applicationtiming provides the best control. For postemergent tropical signalgrass control in Bermudagrass, apply Xonerate 2SC selective herbicide at 14.5 fl oz per acre. Xonerate 2SC Herbicide 14.5 fl oz/A+7.2 fl oz/A Dismiss ® South Herbicide applied 2 times 14 days apart can also be used for TSG control. Ensure the root zone of the desirable turf is healthy and actively growing. Avoid mowing a day after application to allow for full foliar uptake. Reference product label for additional use instructions