| Rimsulfuron and halosulfuron are sulfonylurea herbicides that will control many common weeds in tomato and pepper production. Tomato demonstrates excellent tolerance to these herbicides, but at similar rates pepper has exhibited severe injury. The objectives for this research focused on the characterization of tomato tolerance to rimsulfuron and halosulfuron, by comparison with the sensitive species pepper.; Nine tomato cultivars (‘BHN 444,’ ‘Captiva,’ ‘Carolina Gold,’ ‘Celebrity,’ ‘Cherry grande,’ ‘Equinox,’ ‘FL 47,’ ‘FL 91,’ and ‘Mountain Spring’) were tested for tolerance to rimsulfuron and halosulfuron up to 0.08 kg ai/ha. All cultivars exhibited excellent tolerance to rimsulfuron and halosulfuron applied at labeled rates. ‘BHN 444,’ ‘FL 47,’ and ‘Carolina Gold’ were grown out to yield, without reductions in any cultivars. The application of oxamyl insecticide plus rimsulfuron or halosulfuron did not reduce the shoot weight of any of the nine cultivars. Furthermore, the yields of ‘BHN 444,’ ‘FL 47,’ and ‘Carolina Gold’ were not reduced from halosulfuron and oxamyl combinations.; The target site sensitivity, uptake, translocation, and metabolism of halosulfuron and rimsulfuron was tested in tomato and pepper were tested. The inhibition constants of halosulfuron and rimsulfuron with tomato and pepper acetolactate synthase (ALS) were similar. Tomato and pepper exhibited similar root uptake of halosulfuron (1.7 versus 01.4 nmoles/hr) and rimsulfuron (0.7 and 1.1 nmoles/hr). Foliar uptake of halosulfuron was 0.3 and 0.1 nmoles/hr in tomato and pepper, respectively. Rimsulfuron foliar uptake was 0.56 nmoles/hr in both species. Translocation was less than 8% in both species 72 hours after treatment (HAT).; The majority (63 to 93%) of rimsulfuron absorbed by tomato was metabolized within 24 HAT. This is contrasted by very low metabolism in pepper (87 to 97% of parent compound remained 24 HAT). Abiotic breakdown was less than 20% in all experiments. Based on these data, transformation influenced by metabolic activity appears to be the primary mechanism by which tomato tolerates rimsulfuron. |
