Influence of herbicide application rate and timings for post-emergence control of Sorghum halepense (L.) Pers. maize

Field experiments were carried out in Greece from 1990 to 1992 to study the effect of application timing and rate of nicosulfuron and rimsulfuron on Sorghum halepense (L.) Pers. control and maize yield. All herbicide rates are given in terms of active ingredient (a.i.). Nicosulfuron applied at 22.5, 30.0 and 37.5 g ha^?1 to S. halepense at height 20–35 cm provided greater than 93% control 90 days after treatment, while rimsulfuron applied at 7.5,10.0 and 12.5 g ha^?1 resulted in 81–91% control. Split applications of nicosulfuron and rimsulfuron, as well as tank-mixtures of nicosulfuron+rimsulfuron, gave 91–94% control. Maize yield in all herbicide treatments was greater than that of the weed-infested control and similar to that of the hand-weeded control. S. halepense control with nicosulfuron and rimsulfuron applied to plants 20–35 cm tall was greater than that obtained with their application to plants 5–15, 10–20 or 35–60 cm tall. Rates of 10 and 20 g ha^?1 of rimsulfuron provided control of S. halepense similar to or significantly lower than that achieved with 30 and 60 g ha^?1 of nicosulfuron, respectively. Maize yield produced by all herbicide treatments applied at any time was significantly greater than that of the weed-infested control.