Differential Response of Soybean Cultivars to Metribuzin1

Abstract Metribuzin [4‐amino‐6‐tert‐butyl‐3‐(methylthio)‐as‐triazin‐5(4H)one] controls several species of troublesome annual broadleaf weeds in soybeans [Glycine max (L.) Merr.] but it sometimes causes excessive crop injury. To determine the extent to which this injury is caused by differential sensitivity of cultivars to metribuzin, we evaluated the response of approximately 250 soybean cultivars to soil‐incorporated metribuzin in field experiments in 1973 and 1974. Most cultivars were relatively tolerant of metribuzin at 0.56 kg/ha. At 0.84 and 1.7 kg/ha, many entries were severely injured or killed. Some of the most sensitive cultivars were ‘Altona,’ ‘Hurrelbrink,’ ‘Norman,’ ‘Portage,’ ‘Semmes,’ ‘Tracy,’ and ‘Vansoy.’ These cultivars, and possibly others with only moderate resistance to metribuzin, should probably be avoided when metribuzin is to be used for weed control.