Combinations of Selected Sulfonylurea Herbicides and Diazinon for Yellow Nutsedge Control in Tomatoes

Abstract

In 2008 and 2009 greenhouse and field studies were conducted at Auburn University’s Plant Science Research Center, E.V. Smith Research Station, and Wiregrass Research and Extension Center evaluating combinations of selected sulfonylurea herbicides with the organophosphate insecticide diazinon to determine their combined effect on yellow nutsedge (Cyperus esculentus) control. In 2009, studies were conducted in the greenhouse to evaluate nutsedge emergence with select preemergence applications of halosulfuron, alone and in combination with diazinon. When combined with diazinon, halosulfuron resulted in rate-dependent reductions in yellow nutsedge emergence. A significant interaction was observed with the two pesticides, which suggests they may have a combined effect on yellow nutsedge control. The highest rate of halosulfuron combined with various rates of diazinon offered the greatest level of nutsedge control, ranging from 95 to 100 percent control. In the summer of 2008, a field study was conducted to evaluate nutsedge biomass with preemergence, sprayed and injected, applications of halosulfuron and diazinon alone and combined. A significant interaction was observed between halosulfuron and diazinon. In the summer of 2009, a similar field study was conducted but the injected applications were eliminated due to no differences between sprayed and injected treatments. A synergistic interaction between the two pesticides was observed in the first study but not in the second. In 2009, field studies were conducted to evaluate nutsedge biomass with preemergence combinations of halosulfuron and diazinon. Polyethylene mulch was applied to the second study while the first study was left bare ground. A synergism was not observed in either study. However, the most effective treatment in the second study was the low rate of halosulfuron combined with a high rate of diazinon. In 2009, studies were conducted in the greenhouse to evaluate nutsedge emergence with select preemergence applications of trifloxysulfuron and diazinon alone and combined. In the second study, the highest rate of trifloxysulfuron combined with the highest rate of diazinon offered the greatest level of nutsedge control. A synergistic interaction was observed between the two pesticides in the second study, suggesting that ensuing research should be conducted in the field.