Timing of Flumioxazin Application for Annual Bluegrass Control In Dormant Bermudagrass.

Flumioxazin is used preemergence for weed control in row crops and ornamentals. Flumioxazin also exhibits postemergence activity, characterized by rapid foliar desiccation and necrosis of green tissues. Therefore, this herbicide could be used in warm-season turfgrasses to induce winter dormancy and control winter annual weeds. Research was conducted at the Auburn University Turfgrass Research Unit in Auburn, AL to evaluate flumioxazin application timing for induced dormancy of ‘Tifway’ bermudagrass (Cynodon dactylon x C. transvaalensis) and annual bluegrass (Poa annua) control. Treatments were 0.429 kg flumioxazin ha^-1 applied during the first week of November, December, January, February, March, and April in 2009 and 2010, in addition to a nontreated check. The November application timing resulted in the greatest annual bluegrass control (≥90%), throughout the study. The December application timing resulted in less annual bluegrass control (≥70%). Other application timings resulted unacceptable annual bluegrass control. November and December application timings resulted in induced dormancy of the bermudagrass, which had 100 and 80% green cover at each application timing, respectively. Both of these application timings resulted in more uniformly dormant bermudagrass and therefore more aesthetically pleasing, compared to the nontreated check. Only the April application resulted in delayed spring green-up of bermudagrass. This research indicates that November is the best flumioxazin application timing for annual bluegrass control and induced bermudagrass dormancy.