Velocity Herbicide for Poa Control in Overseeded Turf

Abstract

Velocity, (bis pyrobac-sodium) was applied at different ai/a rates in multiple application series to evaluate treatments for post emergence seed head and vegetative control of Poa annua var. annua. Velocity herbicide, when applied to perennial ryegrass overseed turf with heavy PA infestations, caused periodic discoloration of the ryegrass and yellowing/bronzing of the PA. The leaf yellowing of PA caused by Velocity is in contrast to color enhancement of PA from Proxy/Primo tank mixes. Seed head suppression of PA from Velocity was slightly greater in early April, than in early March. As cumulative treatment amounts of active ingredient of Velocity increased, the seed head suppression increased for treatments beyond the 30 + 30 gm ai/a rate. Above this rate, seed head suppression was increased, but not consistently with the applied active ingredient rate. Seed head suppression of PA on March 5 from Velocity ranged from 35% to 75% among Velocity treatments applied at 30, 45 and 60 grams ai/a. Embark alone had fair seed head suppression from early to mid-March, but decreased dramatically afterwards. There was no benefit of the 30 + 60 gm ai/a treatment, over the 60 + 60 gm ai/a treatment for seed head suppression of PA. Biological response in terms of absolute rate of ai/a applied and response to cumulative amounts of total Velocity were not consistent for PA seed head suppression or vegetative control. No product affectively reduced vegetative control of PA in a highly infested stand of PA which was 40-50% PA. If Velocity is to be competitive against other PA seed head reducing products, rate structures and timings may have to be amended for more multiple applications.