Dry pea (Pisum sativum L.) response to low rates of selected foliar- and soil-applied sulfonylurea and growth regulator herbicides

Field experiments on dry pea (Pisum sativum) were conducted at five locatio ns across the United States in 1995 and 1996 to investigate the effects of low rates of chlorsulfuron, thifensulfuron, and dicamba applied postemergen ce and of chlorsulfuron, metsulfuron, and clopyralid applied preplant incor porated in the soil on pea plants. Although chlorsulfuron, thifensulfuron, and dicamba caused significant injury symptoms on pea plants, they had litt le effect on yield. The lowest rates of foliar applications that caused obs ervable symptoms were 0.035, 0.086, and 1.56 g ai/ha for chlorsulfuron, thi fensulfuron, and dicamba, respectively, whereas chlorsulfuron, thifensulfur on, and dicamba rates that reduced pea yield by 25% were 0.18, 1.36, and 25 g/ha, respectively. Clopyralid caused more injury symptoms than metsulfuro n or chlorsulfuron with soil application. However, the lowest rates of chlo rsulfuron, metsulfuron, and clopyralid that caused observable symptoms were lower than the rates that reduced yield. This study showed that pea plants can sustain some level of plant injury without a large reduction in yield.