Control of Roughstalk Bluegrass (Poa trivialis) with Fenoxaprop in Perennial Ryegrass (Lolium perenne) Grown for Seed

Fenoxaprop applied between late winter and mid-spring selectively controlled roughstalk bluegrass in perennial ryegrass grown for seed in Oregon. Fenoxaprop applied after the arrival of warmer weather in late March had enhanced effectiveness against roughstalk bluegrass compared to earlier application. However, additional delay into April increased damage to perennial ryegrass. Optimum application date coincided with a 15- to 18-cm perennial ryegrass canopy height. Mixed stands of seedling and established roughstalk bluegrass were more consistently controlled by 0.28 kg ai/ha fenoxaprop than by lower rates.