Effects of Light Irradiation and Cutting Height of Turfgrass on Expasion of the Turfgrass Large Patch Disease

Abstract

Effects of light irradiation and cutting height of Zoysia grass on expansion of the turfgrass large patch disease were examined. In fairway of the golf course, a large patch area was divided to two sections. Turfgrass of one section was cut to approximately 18mm of height (high cutting section) and that of another section was done to approximately 8 mm (low cutting section) . Within two weeks of cutting, green turf recovred more prominently in the latter section than the former, although isolation rates of the pathogen were 70-80% in both sections. A similar experiment was done using Zoysia grass grown in a glass house by inoculation of the pathogen. The turf in 60cm× 60cm sections in a plant bed was cut to 25, 35 or 45mm of height. Light (about 1, 000 lux) was irradiated to one half of these sections for only 1 hr in the midnight, Four weeks later disease development was lowest in the irradiated, low cutting section. Scanning microscopy revealed that hyphae of the pathogen grew between sheaths and infection cushions formed on the surface of sheath.An earlier report showed that hyphal growth of the pathogen was remarkably suppressed by light irradiation due to the high sensitivity of the hyphae to low wave-length of light. All these observations suggest that sun light reaches the sheath areas of low-cut turfgrass easily and may suppress growth of hyphae and formation of infection cushions of the pathogen leading to suppression of disease expansion by low cutting of turfgrass in golf courses.