Dissipation of fomesafen in New York state soils and potential to cause carryover injury to sweet corn

The manufacturer's recommended rate for fomesafen in snap beans, dry beans, and soybeans may cause carryover injury in sweet corn. A field experiment, a survey, and multiple greenhouse experiments were conducted to (1) estimate the fomesafen residue concentrations in the soil that might result from use of lower than registered rates, (2) estimate fomesafen residue concentrations in growers' fields and evaluate grower practices for their effects on carryover potential, and (3) investigate the effects of soil type and sweet corn variety on the potential for fomesafen to cause injury to sweet corn. Results of the dissipation study predicted average soil concentrations to be approximately 0.019 mg fomesafen/kg soil at the start of the sweet corn planting season. Half-life values ranged between 28 and 66 d, with an average of 50 d. Residues in grower fields were slightly less than those found in the dissipation study. Injury from fomesafen varied significantly by sweet corn variety and by soil type. Sweet corn grown in soils with high organic matter and low pH were most susceptible to injury from fomesafen. At high rates of fomesafen (0.12 mg/kg), reductions in dry weight of sweet corn varieties ranged from 5 to 60%. At rates of fomesafen slightly higher than those detected in field soils at the time of sweet corn planting (0.03 mg/kg), dry weight either increased slightly (variety trial) or decreased by 6 to 12% (soil-effect trial) depending on soil type. The risk of sweet corn yield losses because of fomesafen carryover appear relatively low. Growers can reduce the risk of carryover injury by planting tolerant varieties in fields where fomesafen was applied the preceding year.