Multiple crop protection pesticides are frequently applied as a tank-mixture for control of a variety of pests in cotton (Gossypium hirsutum). Although chemicals generally act independently, an interaction may occur that can be either beneficial or detrimental to the target crop. The objective of this research was to evaluate the effects of malathion on the absorption and translocation of foliar-applied 14C-trifloxysulfuron (Envoke; Syngenta Crop Protection, Inc.; Greensboro, NC) over a period of 0.25 to 96 h after treatment (HAT) in cotton. Laboratory studies were conducted using 14C-labeled trifloxysulfuron applied alone and in combination with malathion. Greater absorption of radiolabeled trifloxysulfuron occurred in leaves 4 HAT treated with trifloxysulfuron tank-mixed with malathion compared to those treated with trifloxysulfuron alone at the 3-to 4-leaf stage. Translocation of trifloxysulfuron to plant tissue above and below the treated leaf was greater with the tank-mixture. However, increased foliar phytotoxicity (leaf burning) was observed 24 and 96 HAT with trifloxysulfuron tank-mixed with malathion compared to trifloxysulfuron applied alone. These studies suggest malathion could potentially reduce the rate of trifloxysulfuron metabolism in cotton.
