Proper adjuvant selection for foramsulfuron activity

Greenhouse and field studies were conducted to evaluate the activity of foramsulfuron with various adjuvant combinations. Three annual weed species were evaluated in the greenhouse to determine 80% growth reduction (GR ₈₀ values), and five annual weed species were evaluated under field conditions at a reduced dose of foramsulfuron (67%). In the greenhouse, Echinochloa crus-galli L. (barnyardgrass) was the most sensitive species to foramsulfuron, followed by Setaria faberi Herrm. (giant foxtail) and Abutilon theophrasti Medicus (velvetleaf). Adjuvant selection was important for control of these species. The addition of methylated seed oil (MSO) provided the greatest control of these species followed by non-ionic surfactant (NIS) and crop oil concentrate (COC). The addition of a nitrogen fertilizer had a greater effect on weed control for COC and NIS than for MSO with E. crus-galli and S. faberi. However, the addition of a nitrogen fertilizer, 28% urea ammonium nitrate (UAN) or ammonium sulfate, to MSO significantly enhanced A. theophrasti control. In the field, foramsulfuron applied with MSO plus a nitrogen fertilizer provided the greatest level of weed control. Increases in the foramsulfuron dose applied with COC or NIS with a nitrogen fertilizer did not equal the level of weed control achieved with the field dose of foramsulfuron applied with MSO plus UAN.