Shade performance of a range of turfgrass species improved by trinexapac-ethyl

The increased use of enclosed sports stadiums produces shade conditions that seriously affect the quality of turfgrass surfaces, by encouraging undesirable excess vertical succulent growth. Plant growth regulators offer an opportunity to modify a plant’s growth habit, to enable it to be better adapted to a shady environment. To examine growth response to the plant growth regulator, trinexapac-ethyl, cool-season temperate turfgrasses (Kentucky bluegrass–perennial ryegrass, Poa pratensis L./Lolium perenne L.; creeping bentgrass, Agrostis palustris Huds.; supina bluegrass, Poa supina Schrad.; and tall fescue, Festuca arundinacea Schreb.) and a warm-season species (Bermudagrass, Cynodon dactylon L.) were established in a field experiment. Main treatments were 4 levels of shade (0, 26, 56 or 65% shade), with or without trinexapac-ethyl at a rate of 0.5 kg/ha. A pot experiment measured the vertical shoot growth rates of Kentucky bluegrass–perennial ryegrass and tall fescue under 0, 56 or 65% shade, with and without trinexapac-ethyl. Both experiments were conducted under ambient conditions. Light readings taken in full sunlight, at midday through summer and autumn (major period of assessment), ranged from 1350 to 1950 µmol/m2.s. Trinexapac-ethyl reduced vertical growth of all turfgrass species. This resulted in decreased clipping weights and in clipping material having an increased dry matter percentage (i.e. reduced succulence). The impact of trinexapac-ethyl on sward quality and colour was dependent on shade level, for all species. At 56 and 65% shade, quality and colour improvement was maximised with trinexapac-ethyl application; the magnitude of improvement was dependent on species, with Kentucky bluegrass–perennial ryegrass and bentgrass showing the most benefit. It was concluded that trinexapac-ethyl improved the shade performance of a number of turfgrass species commonly used in high quality turf surfaces. It may offer the potential to reduce costs of managing turf in such an environment.