Separation and quantitation of the sources of dew on creeping bentgrass

Many fungal pathogens require free water to cause infections. In high-maintenance turfgrass systems, accumulations of dew are an important source of this water. Little is known about the amount or rate of dew accumulations on turfgrasses under golf course maintenance regimes. Experiments were conducted in 1994 and 1995 to measure separately the different sources of dew as they accumulated throughout the night on irrigated creeping bentgrass (Agrostis palustris Huds.) maintained as a golf fairway. Sources of dew were separated as (i) condensate and (ii) plant-generated moisture (wound exudates plus guttation). Additionally, re-accumulating moisture was measured from original collection sites at 0800 h to establish amounts and rates of re-accumulation after displacement, and the optimal time to displace dew to achieve maximum reductions of dew periods. Mean total dew measured at 0800 h over both years was 0.195 mm, 33% of which was plant generated. Moisture re-accumulating following displacement had a higher proportion of plant-generated moisture, g ranging from 46 to 77% depending on the time of the observation. Condensate and plant-generated moisture accumulated at similar rates over time. Significant amounts of total dew re-accumulated following displacement prior to 0400 h, indicating that dew displacement prior to that time may be much less efficient at reducing the duration of leaf wetness episodes, regardless of the displacement method used.