Evaluation of Fungicides for Control of Rapid Blight of Poa trivialis in fall 2006

Abstract

Rapid blight is a new disease of cool season turf grasses caused by Labyrinthula terrestris, an organism in a group referred to as the marine slime molds. A trial was conducted in fall 2006-winter 2007 to repeat an evaluation of efficacy of different rates and intervals of Insignia fungicide and elemental sulfur, both of which gave acceptable control in trials in 2005. The trial was conducted at a golf course in central Arizona with a previous history of disease and high salinity irrigation water (about 5 dS/m). Plots were established in August 2006 on a practice tee on which Champion 419 bermudagrass was overseeded with Poa trivialis "Laser". Treatments included pyraclostrobin (Insignia) as a preventive and as a curative, pyraclostrobin (Insignia) combined with Fore as a preventive, and elemental sulfur (DsiperSul) as a preventive. Disease symptoms appeared immediately after the first mowing. Disease ratings 15 days after first mow showed that applications of the high rate of Insignia at first mow gave excellent control. Moderate control was shown in applications with early applications of Fore combined with the lower rate of Insignia. Treatments with Insignia as a curative and with sulfur as a preventive were not acceptable.