Turf Safety and Effectiveness of Dithiopyr and Quinclorac for Large Crabgrass (Digitaria sanguinalis) Control in Spring-Seeded Turf

Abstract

There are limited options for controlling large crabgrass in spring-seeded cool-season turf. The objective of this experiment was to evaluate the safety and effectiveness of dithiopyr and quinclorac to control large crabgrass in spring-seeded Kentucky bluegrass and perennial ryegrass stands. Quinclorac at 0.84 kg/ha and dithiopyr at 0.56 kg/ha were applied separately at various times prior to seeding and after emergence of Kentucky bluegrass and perennial ryegrass. Quinclorac applied once at 2, 4, 8, or 12 weeks after emergence (WAE) or split-applied preplant incorporated (PPI) + 12 WAE will give season-long control of large crabgrass with no injury to spring-seeded Kentucky bluegrass or perennial ryegrass. Quinclorac applied PPI or 0 WAE is safe to use in spring seedings, but it will not provide season-long control of large crabgrass. Dithiopyr applied 2 or 4 WAE will control large crabgrass season-long while not injuring spring-seeded Kentucky bluegrass or perennial ryegrass. However, dithiopyr applied PPI or 0 WAE will severely limit germination of desirable turf, and dithiopyr applied 8 or 12 WAE will not control mature crabgrass.