Evaluation of the Differential Responses of Common Bermudagrass (Cynodon dactylon) Varieties to Aryloxyphenoxypropionate Herbicide Fenoxaprop-p-Ethyl.

Aryloxyphenoxypropionate (AOPP) herbicides, such as fenoxaprop and fluazifop, are promising for selective control of bermudagrass (Cynodon dactylon (L.) Pers.) in various warm- and cool-season grasses. However, variation in response to AOPP herbicides may exist among different bermudagrass cultivars. This greenhouse based study was conducted to evaluate the sensitivities of five bermudagrass cultivars, ‘Princess 77’, ‘Celebration’, ‘NuMex Sahara’, ‘Riviera’ and ‘Yukon’ to fenoxaprop-p-ethyl at 0.2 kg ai ha^-1. Treatment included five bermudagrass cultivars listed above with or without fenoxaprop treatment, and was arranged in a randomized complete block design with four replications. Sensitivities of various bermudagrass cultivars to fenoxaprop were evaluated weekly as discoloration and clipping biomass. Results showed that the tested bermudagrass varieties have significantly different tolerance to fenoxaprop. Among all of the bermudagrass cultivars, ‘Riviera’ and ‘Yukon’ showed less sensitivity to fenoxaprop with 21 to 43% less injury and 3- to 5-fold more clipping biomass produced compared to the other cultivars. The most sensitive cultivar was ‘Celebration’, which resulted in 43% more discoloration and up to a 5-fold greater reduction in clipping biomass compared to ‘Yukon’. Our results suggest that there is a significant intra-species variation among common bermudagrass varieties in response to AOPP herbicide, and this variation should be considered before developing a herbicide program for managing bermudagrass.