effect of bendioxide and 2,4-DB on the early growth and leaf development of three soybean (Glycine max (L.) Merr.) cultivars and the control of morning glory (Ipomoea purpurea (L.) Roth.)

Three soybean (Glycine max (L.) Merr.) cultivars (Edgar, Duiker and Komati) were grown in pots together with morning glory (Ipomoea purpurea (L.) Roth.). Plants were exposed to three levels of bendioxide (0, 0.96 and 1.44 kg a.i. ha −1 ) in combination with four levels of 2,4-DB (0, 22, 34 and 45 g a.i. ha −1 ) to gauge the most effective herbicidal combination to control morning glory without affecting the growth of different soybean cultivars. All soybean cultivars responded similarly to the application of herbicide. The combination of both herbicides at the highest levels significantly reduced soybean leaf area and mass one week after application. Bendioxide applied alone at 1.44 kg ha −1 , and the combination of bendioxide (0.96 kg ha −1 ) with 2,4-DB (22 g ha −1 ) reduced soybean leaf mass two weeks after application. The recovery of soybeans from all treatments after three weeks following application was rapid and complete. The addition of 2,4-DB to bendioxide enhanced the lethality of the herbicide to morning glory. Combinations of 0.96-1.44 kg ha −1 bendioxide with 34-45 g ha −1 2,4-DB gave the best control of morning glory.