DOLLAR SPOT AND GRAY LEAF SPOT SEVERITY AS INFLUENCED BY IRRIGATION PRACTICE AND PLANT PROTECTION MATERIALS

Agrostis stolonifera and Lolium perenne are widely used turfgrass species grown on golf fairways, however, they are susceptible to dollar spot (Sclerotinia homoeocarpa) and gray leaf spot (Pyricularia grisea) diseases, respectively. Two field studies were conducted to assess: 1) the influence of two irrigation regimes and seven chemical treatments on dollar spot and gray leaf spot severity; and 2) the effects of two spray volumes (468 and 1020 L water ha-1), two fungicides (chlorothalonil and propiconazole) and three application timings (dew present or displaced and dry canopy) on dollar spot control. Dollar spot was more severe in A. stolonifera subjected to infrequent irrigation; whereas, gray leaf spot was more severe in frequently irrigated L. perenne. The plant growth regulator and wetting agent evaluated suppressed dollar spot, but they had no effect on gray leaf spot. Chlorothalonil was most effective when applied to a dry canopy in 468 L water ha-1