Sequential Postemergence/Preemergence Treatments for Crabgrass Control in Bermudagrass Turf

Abstract

Abstract Crabgrass (Digitaria spp.) was controlled in common bermudagrass [Cynodon dactylon (L.) Pers.] with postemergence (POST) and preemergence (PRE) herbicides on a tropical island of Guam. The recommended label rates of PRE herbicides oxadiazon at 3.4 kg/ha (3.0 lb/A), pendimethalin at 3.4 kg/ha (3.0 lb/A), and dithiopyr at 0.6 kg/ha (0.5 lb/A) were applied initially and one-half recommended rates were applied to one-half of the plots 8 weeks later. MSMA was applied as the POST herbicide treatment in 1, 2, or 3 applications. The first MSMA treatment was applied in sequence with the PRE herbicides and followed by either 1 or 2 additional MSMA applications at 1 or 1 and 2 weeks after the initial MSMA application. Two weekly applications of MSMA assured complete control of existing crabgrass. Single applications of pendimethalin, oxadiazon, and dithiopyr at full rates assured ≥90% control for a period of 20 to 26 weeks during the rainy season and for 6 to 12 weeks during the dry season. There was no advantage of the second PRE treatments at a reduced rate. On fairways where crabgrass infestation was 95%, an application of MSMA resulted in severe turf discoloration lasting 5–6 weeks.