Evaluation of a Petroleum‐Derived Spray Oil for Control of Microdochium Patch and Turfgrass Spring Performance on Nordic Golf Greens

Abstract

Core Ideas Mineral oil was as effective as or more effective than fungicides in controling Microdochium patch. Repeated applications of mineral oil in autumn might inhibit turfgrass green‐up in spring. Mineral oil can reduce conventional fungicide use on Nordic golf courses. Greenkeepers are looking for alternatives to fungicides for control of turfgrass diseases. Our objective was to evaluate a petroleum‐derived spray oil with a blue‐green pigment for control of Microdochium patch/pink snow mold (Microdochium nivale) on golf course putting greens with various durations of snow cover. The spray oil was applied at rates 27 or 54 L ha−1 every third week from late August or September to December, either alone, in tank mixture with potassium phosphite (3 kg PO3 ha−1) or in tank mixture with half rate of fungicides approved for turf, in five 1‐yr trials in the Nordic countries. The oil was as effective or more effective than fungicides and gave, on average, 94 and 98% disease control at rates 27 and 54 L ha−1, respectively. Tank mixtures with half rate of prochloraz + propioconazole and fludioxonil did not increase disease suppression in a trial with 79 d snow cover. Phosphite reduced disease severity in one trial only and did not improve disease control or turfgrass quality when tank‐mixed with the oil. The pigment in the spray oil was highly persistent and improved turfgrass greenness except in a trial where the combination of oil and ice cover gave a transitory black color at ice melt. Another trial with long snow cover showed a drop in turfgrass quality in spring as the spray oil prevented normal green‐up. In conclusion, this research shows that a spray oil has the potential to reduce fungicide use on Nordic golf courses.