Effects of Spray Nozzle and Fungicide Mobility on Control of Microdochium Patch on an Annual Bluegrass Putting Green.

Microdochium patch (Microdochium nivale) is a major disease on annual bluegrass (Poa annua) golf courses in the Pacific Northwest, Canada, and Northeastern coastal states.  Currently, the only way to control this disease is through repeated fungicide sprays.  However, little is known about the effects of spray nozzle type used in combination with varying fungicide mobility on control of this disease.  A two year field study was conducted at Oregon State University’s Lewis-Brown Horticulture Farm to evaluate the effects of four spray nozzles and three fungicides with different mobility (contact or no mobility, translaminar, and acropetal) on control of Microdochium patch on a sand-based putting green with annual bluegrass (Poa annua).  The trial was designed as a 4 by 3 factorial plus control with 2.3 m² plots arranged in a randomized complete block with four replications. The fungicides were applied with four different nozzles (XR1104 and XR1108 Flat Fans which produce medium and course droplets, resepctively, and the TurfJet Flat Fan 1/4TTJ04 and 1/4TTJ08, which produce extremely coarse droplets) and two flow rates (1.3 and 2.6 L m^-1 at 30 PSI) of each type.  The two nozzles sizes were used in order to maintain the same number of droplets at two different spray volumes: 407 and 814 L ha^-1.  Secure, A8574D, and Banner Maxx II were applied at 1.6, 1.3, and 3.2 L ha^-1.  Five applications were made three weeks apart with the last application made in the third week of April.   The fungicides were applied with a CO₂-powered backpack sprayer with a 3 nozzle hand-held boom at 30 psi.  Speed was calibrated with a metronome.    The XR nozzles provided better control of Microdochium patch than the TTJ nozzles for all fungicides.