EFFECTS OF TEMPERATURE AND NITROGEN FERTILIZER ON MESOTRIONE ACTIVITY AGAINST ANNUAL BLUEGRASS (POA ANNUA L.)

摘要

cool-season turfgrass,but selective control is difficult.The 4- hydroxyphenylpyruvate dioxygenase (HPPD) inhibitor,mesotrione,has activity against annual bluegrass (ABG) and excellent safety to desirable cool-season turfgrasses.However,sequential mesotrione applications are required for complete ABG control.Additionally,ABG control with mesotrione is very inconsistent across seasons,years,and locations.Growth chamber experiments were conducted at the University of Tennessee to examine the influence of air temperature and nitrogen fertilization on mesotrione activity against ABG.Plants were subjected to HIGH (32/26°C dayight) and LOW (24/18°C dayight) temperature regimens and treated with the factorial combination of mesotrione (0 or 280 g ha-1) and nitrogen (N) fertilizer (5 or 54 kg ha-1).ABG visual injury and chlorophyll fluorescence yield (Fv/Fm) were evaluated 7,14 and 21 days after treatment (DAT).Aboveground biomass was also measured 21 DAT.Mesotrione activity was highest when ABG was treated with 54 kg N ha-1 and grown under LOW temperatures,but never exceeded 40% visual injury.Visual injury of mesotrionetreated plants subjected to HIGH temperatures and treated with 54 kg N ha-1 was < 20%,but greater than that of plants treated with 5 kg N ha-1 at 7 and 14 DAT under the same temperature regimen.Visual injury never exceeded 5% when plants were treated with only 5 kg N ha-1 regardless of temperature regimen.These results indicate that while both N fertilization and air temperature affect mesotrione activity against ABG,N fertilization has the greatest impact on activity for the temperature regimens evaluated in this experiment.Future research should evaluate the influence of N fertilization and sequential mesotrione applications on ABG control under field conditions.