Managing Microdochium Patch Using Non Traditional Fungicides.

Microdochium nivale is a major turfgrass disease in cool, humid regions. Currently, traditional fungicides are the only known methods of control. Increasing pesticide restrictions have generated concern regarding management of M. nivale.  The objective of this research is to evaluate rolling, as well as the application of mineral oil, sulfur and potassium-phosphite as fungicide alternative options of M. nivale on Poa annua putting greens. A field experiment was initiated in September 2013 and concluded in June 2014 on putting greens built using USGA sand at Oregon State University, Corvallis, OR and Washington State University, Puyallup, WA.  Experimental design was a 2 by 2 by 2 by 4 randomized complete split-block design, with four replications.  Factors included location, rolling, mineral oil and winter fertilization.  Rolling was applied 5 days a week and compared to an unrolled control.  Mineral oil (Civitas One) was applied every other week at a rate of 19.94 Kg a.i./ha^-1 and compared to a control. Winter fertilization treatments included sulfur (Sulfur DF) applied at 9.77 Kg S/ha^-1, potassium-phosphite (PK Plus) applied at 3.66 Kg H₃PO₃/ha^-1 and a combination of sulfur and potassium-phosphite applied at these respective rates, in addition to an untreated control. Turf quality (1-9 scale, with 6 or greater considered acceptable) and percent disease (0-100%) data were collected weekly. In Corvallis, Civitas One applied in combination with PK Plus, Sulfur DF or PK Plus and Sulfur DF provided the greatest reduction in disease, (>98% control). Rolling alone (>30% disease), Sulfur DF alone (>4%) and PK Plus alone (>3% disease) provided the poorest disease suppression. Regarding turf quality, unrolled treatments of Civitas One applied in combination with PK Plus, Sulfur DF or PK Plus and Sulfur DF produced the best results (­≥7.4).  Rolled plots of the same treatments resulted in poorest quality due to abiotic damage.