Established perennial weeds, both grasses and broadleaves, must be controlled with postemergence herbicides. Control is improved at this stage because young weeds readily absorb and translocate herbicides. Early weed control also provides an opportunity for turfgrasses to fill in the bare areas left by dying weeds. The risk of injury from postemergence herbicides is greater during the green-up process than when the turfgrass is fully dormant or actively growing. Weeds that are stressed due to dry weather, heat, or other environmental factors are more difficult to control with postemergence herbicides.
F increase the risk of turfgrass injury.
The resistance of postemergence herbicides to wash-off by rainfall or irrigation varies among products. Typically, a rain-free period of 6 to 24 hours is sufficient to avoid a reduction in effectiveness. Even if rain falls soon after application, some degree of reduced control will be achieved. Mowing can affect performance of postemergence herbicides. Avoid mowing three to four days before application for greater leaf area to intercept the spray.