Dimension Herbicide as a Potential Product for Pre-Emergence Pos Annual Control on Overseeded Bermudagrass Turf

Abstract

Dimension herbicide (dithiopyr) was applied to common bermudagrass turf at 90, 60, and 45 days before fall overseeding to measure the efficacy for turf safety and for control of fall germinating POA Annua (PA). Applications were made at 0.25, 0.375, and 0.50 lbs. AI/A on each date. One half of each plot was overseeded, while the other half was not. Percent plot (PA) infestation and percent weed control was more greatly affected by the process of overseeding, than that of the herbicide applications alone. When not overseeded, the bermudagrass turf had a maximum of 45% PA control in November, which decreased dramatically to little or no control from January to March 2000. With the inclusion of ryegrass overseed, the high rate (0.50 lbs. AI/A) applied closest to the overseeding (45 DBOS) provided between 79-82% PA control over the length of the test. Actual infestation levels among non-chemical receiving control plots showed a 3X increased level in PA suppression due to overseeding, when compared to the non-overseeded, non-chemical controls. Dimension herbicide alone had little effect for PA control. When combined with overseeding, the 0.50 lb. AI/A rate, applied at 60 or 45 DBOS provided the greatest levels of PA control. The performance of Dimension on non-overseeded bermudagrass does not support the anticipated use of this chemical for PA control.