Enzhan Song, Daniel T. Lloyd, Reid J. Smeda and Xi Xiong*

Division of Plant Science, University of Missouri, Columbia, MO, 65211

*xiongx@missouri.edu

Bermudagrass (Cynodon spp.) and zoysiagrass (Zoysia spp.) are important warm-season grasses in the southern United States and across the transition zone. Although both of these species could be used on golf course fairways, mixtures of the two species seriously reduces turf quality and playability due to their incompatible colors and textures. In Missouri, a majority of the golf course fairways are occupied by zoysiagrass, and bermudagrass infestations have become a common problem in recent years. When growing out of place, bermudagrass is difficult to eliminate as there is no selective herbicide that provides effective control without seriously injuring zoysiagrass. In this experiment, eleven herbicides were tested under greenhouse conditions with two varieties of common bermudagrass (C. dactylon (L.) Pers.), ‘Riviera’ and ‘Quickstand’, and two varieties of zoysiagrass (Z. japonica Steud.), ‘Mayer’ and ‘El Toro’.  Promising treatments were applied under field conditions at two locations in 2010 and 2011.  The experimental design was a completely randomized block with four replications. Fenoxaprop-p-ethyl in combination with triclopyr resulted in ~80% bermudagrass suppression within two weeks after treatment (WAT) with minimal injury to zoysiagrass. Although fluazifop in combination with triclopyr only showed 40% control in the greenhouse, it achieved 90% control in the field. During our early experiment, different bermudagrass varieties showed different levels’ tolerance to fenoxaprop application. Therefore, a separate greenhouse study was established to evaluate herbicide tolerance of six common bermudagrass varieties. All of the tested varieties showed significant herbicide injury within 5 days after treatment. The only exception was ‘Riviera’, which showed symptoms of injury 2 days after treatment. After eight WAT, ‘Celebration’ appeared to be the most susceptible variety to fenoxaprop treatment, and its clipping biomass reduced ~60% compared to untreated control. Other varieties, such as ‘Quickstand’, recovered rapidly and showed no signs of herbicide injury by 8 WAT.