Monday, 7 November 2005
5

Bermudagrass Root Growth Response to Foliar Applications of Imazapic Herbicide.

Robby Glasgow and Case Medlin. Oklahoma State University, 812 Glasgow Rd., Petrolia, TX 76377

Bermudagrass (Cynodon dactylon) is a grass extensively used as a pasture forage in the Southeast United States, Texas, Oklahoma, California, and can be found in other states as well. This warm-season grass spreads mainly vegetatively by rhizomes and stolons, although it can also reproduce by seed. Bermudagrass is a sod-forming grass which does not grow much taller than around 70 cm (2 feet) which is commonly grazed or mechanically harvested for hay. Summer grass weeds, such as johnsongrass (Sorghum halepense), foxtail (Setaria spp.), and field sandbur (Cenchrus incertus) are common problem in bermudagrass pastures. In the early 2000's, imazapic was registered for control of many grassy weeds in bermudagrass, however, after only a few years on the market the label was changed making it illegal to use the product on bermudagrass pastures. This label change was primarily due to foliar injury on the bermudagrass causing in some cases total forage loss for the treatment year. However, researchers have observed that large bare spots resulting from successful control of weeds quickly fill in with bermudagrass, thus increasing forage production and hay quality the following year. Therefore, the objective of this research was to evaluate the root growth response of bermudagrass when its foliage was treated with various imazapic rates. Randomized complete block experiments have been conducted to evaluate the impact of imazapic applied at ___, ___, ___, and ___ lb ai/A in greenhouse grown bermudagrass microplots. Four months after treatment, foliage was removed from the microplots and the roots were washed thoroughly and weighed to determine if imazapic impacts root growth when compared to an untreated control treatment.

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