Johnsongrass, a tall, coarse, perennial grass, is the second most common and troublesome weed in field corn in Texas. Field experiments were conducted in 1996 to 1998 to evaluate an integrated johnsongrass management program in bedded and irrigated field corn. Nicosulfuron at 26.3 g ai/ha applied banded over the row to 50% of the planted area plus one cultivation resulted in johnsongrass control of aboveground and rhizome biomass and in corn yield comparable to the labeled rate (35 g ai/ha) when applied two consecutive years in the same plots. This treatment reduced cost 27% and reduced herbicide input 62% compared to nicosulfuron applied broadcast at labeled rate without cultivation. Economic benefits of this johnsongrass management program are promising for field corn producers.

Kochia (Kochia scoparia) control dropped from about 90% to less than 20% after three consecutive annual applications of acetolactate synthase (ALS)-inhibiting herbicides in several northeastern South Dakota fields. Field experiments were conducted to evaluate control of kochia resistant to ALS-inhibiting herbicides using combinations of herbicides applied postemergence (POST) in wheat (Triticum aestivum) and using herbicides applied preemergence (PRE), POST, and PRE plus POST in soybean (Glycine max). Thifensulfuron plus tribenuron did not control kochia in wheat (> 600 kochia plants/m2 at harvest) and wheat yield was similar to yield of the untreated control. Dicamba plus 2,4-D (in 1996) and bromoxynil plus MCPA (in 1996 and 1997) controlled kochia and increased yields by 15% or more. Kochia was sparse (less than 1 plant/m2) in soybean plots, but grass weeds were prevalent. PRE plus POST or POST herbicide combinations that included ALS-inhibiting herbicides controlled grasses, and soybean yields were as much as 20% greater than yields with combinations that did not contain ALS-inhibiting herbicides. Adding ALS-inhibiting herbicides to wheat herbicide combinations decreased profitability because treatment costs increased while yields did not. In contrast, adding ALS-inhibiting herbicides to soybean treatments increased profitability due to better grass control, resulting in increased yield and better return.