Isolation of the Rapid Blight Pathogen Labyrinthula terrestris from Bermudagrasses in Arizona

Abstract

Rapid blight is a new disease of cool season turfgrasses that affects several important turfgrasses used for overseeding Bermuda in Arizona such as Poa trivialis and Lolium perenne (perennial rye). It is caused by Labyrinthula terrestris, an unusual organism that causes collapse of susceptible hosts and usually occurs in turfgrasses irrigated with moderate to high salinity irrigation water (EC>2.0). Rapid blight has not been observed in the field in warm season grasses such as Cynodon sp. (Bermudagrass) although laboratory trials have shown that common Bermudagrass and other grasses may be hosts. Because the survival mechanism of Labyrinthula terrestris in the absence of cool season turfgrass hosts was unknown, this study was initiated to determine if L. terrestris "over-summers" in different Bermudagrass systems. Results of assays of several different Bermudagrass systems show that Bermudagrasses are good hosts for L. terrestris and explains why rapid blight is a perpetual threat year after year in the same locations.