Tolerance of Tomato to Herbicides Applied through Drip Irrigation

Greenhouse and field studies were conducted to determine tolerance of tomato to halosulfuron, imazosulfuron, and trifloxysulfuron herbicides applied through drip irrigation. In greenhouse studies, PRE- and POST-applied trifloxysulfuron caused greater tomato injury (14 and 54% injury, respectively) than PRE- and POST-applied halosulfuron (5 and 26% injury, respectively) or imazosulfuron (5 and 23% injury, respectively). All herbicide treatments in the greenhouse studies caused greater injury to tomato than the nontreated. Greater tomato injury was observed in the greenhouse from herbicides applied POST than when soil applied. Tomato injury from POST-applied halosulfuron, imazosulfuron, or trifloxysulfuron followed a linear relationship, with tomato injury increasing with increasing herbicide rate. Tomato photosynthetic rate did not differ among the herbicide treatments (32.7 to 55.0 μmol m⁻² s⁻¹) and the nontreated (38.0 to 55.0 μmol m⁻² s⁻¹). At 5 to 16 days after treatment (DAT), tomato treated with imazosulfuron POST (0.26 to 0.46 cm s⁻¹) or trifloxysulfuron POST (0.27 to 0.51 cm s⁻¹) had lower stomatal conductance compared to the stomatal conductance of the nontreated tomato (0.65 to 0.76 cm s⁻¹). Chlorophyll content did not differ among treatments at 0 to 6 DAT. At 7 to 12 DAT, tomato treated with imazosulfuron POST (34.0 to 40.1 SPAD) and trifloxysulfuron POST (35.0 to 41.6 SPAD) had lower chlorophyll content compared to the nontreated (39.1 to 48.1 SPAD). In 2008 and 2009 field studies, no tomato injury was observed. Herbicide, herbicide application method, and herbicide rate had no effect on tomato height (73 to 77 cm 14 DAT, 79 to 84 cm 21 DAT) and total fruit yield (62,722 to 80,328 kg ha⁻¹).Nomenclature: Halosulfuron; imazosulfuron; trifloxysulfuron; tomato; Solanum lycopersicum L.