| Abstract/Contents: | "Two prevalent annual grassy weeds growing in bermudagrass fairways in southern United States are annual bluegrass (Poa annua), a winter annual, and crabgrass (Digitaria ischaemum), a summer annual. In the Midwest and Northeast, effective crabgrass control has been obtained from herbicides applied the previous fall. Five tests were conducted on two golf courses from 1990 to 1993, to evaluate year around grassy weed control and secondly crabgrass control from a single herbicide application in the fall compared to a fall application plus a spring application. The fall application herbicide rate was at the usual label rate. Reduced rates, one-third, one-half, or two-thirds of the full rate, were applied in the fall plus the spring. Herbicides and rates evaluated were: benefin at 3.36 kg ha-1, benefin at 3.36 followed by oryzalin at 1.68 kg ha-1 in the spring, benefin + trifluralin at 3.36 kg ha-1 and 1.68 + 1.68 kg ha-1, DCPA at 11.71 kg ha-1 and 11.77 + 6.17 kg ha-1, dithiopyr at 0.84 kg ha-1 and 0.56 + 0.28 kg ha-1, oxadiazon at 3.36 kg ha-1 and 2.24 + 2.24 kg ha-1, pendimethalin at 3.36 kg ha-1 and 1.68 + 1.68 kg ha-1, and Prodiamine at 0.84 kg ha-1 and 0.56 + 0.28 kg ha-1. Fall applications were October 4 to 10 and spring applications March 6 to 12. Plot size was 1.5 × 3.0 or 4.5 m. A RCB design was used with four replicates. Sprayable herbicides were applied in 308 L ha-1 of water. Granular herbicides, oxadiazon and benefin + trifluralin, were applied with a shaker can. The herbicides applied in early October, with the exception of DCPA, provided effective annual bluegrass control (≥ 86% data based on an average of all tests with visual ratings made from March 10 to April 23). This was true whether applied as a single application at the full rate or at a reduced rate. Split applications, fall plus spring, did not increase annual bluegrass control. None of the herbicides applied in only October effectively controlled smooth crabgrass (Digitaria ischaemum) throughout the following summer. However, dithiopyr, pendimethalin, Prodiamine, and oxadiazon applied in October and March, at a reduced rate, for each application gave excellent control of both annual bluegrass and smooth crabgrass (The average rating for the five tests from observations made September 1 to 9 for smooth crabgrass was ≥ 89%). Thus, in a year around weed management program, these four herbicides applied in timely split applications can effectively control both annual bluegrass and smooth crabgrass in a bermudagrass fairway. Prodiamine, dithiopyr, pendimethalin, and oxadiazon may also be safely applied to perennial bluegrass, tall fescue, and perennial ryegrass. No overseeding or reseeding could be done in these cool-season grasses nor in a bermudagrass fairway when following this herbicide program." |
|---|
