Evaluation of Flumioxazin Programs with Postemergence Herbicides for Winter Annual Weed Control.

Annual bluegrass (Poa annua L.) is a problematic weed that reduces turfgrass aesthetics and functionality. Flumioxazin provides pre- and postemergence control of annual bluegrass but application timings are limited to dormant bermudagrass (Cynodon dactylon L.). A field experiment was conducted from October 2013 to May 2014 in Griffin, Georgia to evaluate winter annual weed control programs from sequential treatments of flumioxazin with other herbicides in dormant bermudagrass. The experiment was established as a randomized complete block design with four replications of 1 x 3-m plots. Treatments were applied with a single 9504E flat-fan nozzle calibrated to deliver 374 L ha^-1 with a CO₂ pressured sprayer. Prodiamine applied in fall followed by (fb) simazine applied in winter fb prodiamine applied in late winter provided good (80 to 89%) control of annual bluegrass from March to May. Prodiamine applied in fall, winter, and late winter fb dithiopyr applied in late winter provided poor (<70%) to fair (70 to 79%) control of annual bluegrass and poor control of white clover (Trifolium repens L.). However, sequential treatments of herbicides including flumioxazin applied in winter gave excellent (90 to 100%) annual bluegrass control from December to May. Prodiamine applied in fall fb simazine applied in winter fb prodiamine applied in late winter provided good control of white clover in February and March. Sequential herbicide treatment programs excluding flumioxazin provided poor dandelion (Taraxacum officinale G.H. Weber ex Wiggers) control from February to May. In contrast, sequential treatment programs including flumioxazin provided good to excellent control of white clover and common dandelion from February to May. Bermudagrass greenup was not reduced from the nontreated by any treatment. Overall, results suggest that sequential herbicide programs including flumioxazin increased annual bluegrass, white clover, and dandelion control in dormant bermudagrass from regimens with simazine and other preemergence hrbicides.