Weed Control in Snap Beans and Edamame with Fomesafen (Reflex) Herbicide (2013)

Research report to the Oregon Processed Vegetable Commission

Ed Peachey
OSU Department of Horticulture

The objectives were to evaluate crop safety and weed control with fomesafen (Reflex, not a registered treatment) applied to snap beans at Stayton and Corvallis, and fomesafen and sulfentrazone (Spartan, not a registered treatment) applied to edamame at a site near Keizer. Lambsquarters continues to evade many weed control programs, and the use of Raptor on a majority of snap beans acres is exerting a selection pressure that may undo the weed control successes we have had over the last decade.

Fomesafen caused very little injury to snap beans at two sites (Stayton and Corvallis) when applied PRE. When applied EPOST, injury at the Corvallis site was greater than at Stayton. Tank mixes with Dual Magnum were extremely effective on lambsquarters, even though lambsquarters was poorly controlled by fomesafen applied alone. Fomesafen provided better lambsquarters control at this site than at the Stayton site, but did not control lambsquarters when applied EPOST. The greatest yield at Corvallis was a tank mix of fomesafen and Dual Magnum at the 1 pt rate of each. Yield followed weed control with the possible exception of fomesafen PRE fb Sandea EPOST, indicating that Sandea may have seriously injured the beans.  At Keizer, injury to edamame was visible in two of the three replications in plots treated with sulfentrazone at 12 oz/A (Table 3). However, one of these plots was in a low and wet area in the field, which may have exacerbated crop injury. No injury was noted with fomesafen. Crop emergence may have been slightly reduced by the 2x rates of both sulfentrazone and fomesafen, but no signs of crop injury were visible at the midseason rating. There was very little statistical evidence that edamame yield was influenced by either herbicide, but trends did suggest a possible suppression of pod yield at the 2x rates of both herbicides. Weeds were so scarce in this experiment that weed control ratings were not possible and weed competition with the crop was not a factor in determining yield.