Selective Preemergence and Postemergence Control of Panic Liverseedgrass (Urochloa panicoides) in Desert Turf.

A relatively new problem weed is occurring in the low desert turf of Arizona. Panic liverseedgrass (Urochloa panicoides) was about 7.6 cm tall when mowed weekly in lesser maintained common bermudagrass turf, and maturing seedheads were present when initially treated on 02 June 2016 with postemergence herbicides. In Phoenix, AZ, herbicide treatments were applied with a backpack CO₂ sprayer to small plots and a sequential application was sprayed on 15 June. A second experiment evaluating tank-mix combinations with mesotrione and topramezone was initiated on 16 June 2016. A sequential application was sprayed on 12 July followed by a third application on 04 August. In experiment 1 that compared several postemergence herbicides, topramezone demonstrated activity while quinclorac and the pre-mix of quinclorac plus sulfentrazone plus 2,4-D plus dicamba and ALS-enzyme inhibiting metsulfuron and sulfosulfuron did not exhibit adequate acceptable activity against the mature liverseedgrass. In experiment 2, all treatments of mesotrione and topramezone demonstrated activity on liverseedgrass following the initial application. Mesotrione combined with metribuzin or simazine and topramezone plus quinclorac exhibited liverseedgrass moderate liverseedgrass reduction. Alone, mesotrione and topramezone exhibited a bleaching effect on the grasses. The combination with simazine or quinclorac caused less bleaching and more burning effect on the grasses. Overall, acceptable control of liverseedgrass was not achieved with multiple postemergence herbicide applications on the maturing weed. Preemergence herbicides were applied to dormant bermudagrass turf in two field experiments in Phoenix, AZ on 19 December 2016 and 24 February 2017. Pendimethalin, prodiamine and pendimethalin plus dimethenamid granular formulations offered acceptable near complete control when applied during the winter to early spring seasons. Indaziflam and flumioxazin provided acceptable reduction with December spray applications as liverseedgrass appeared in March.