Herbicide Program to Control Parthenium hysterophorus in Grain Sorghum in an Arid Environment

Parthenium weed (Parthenium hysterophorus L.) is an emerging production constraint in many summer crops including sorghum (Sorghum bicolor L. Moench), but limited control options are available. In this field study, the efficacy of sole and sequential applications of a pre-emergence (pendimethalin) and a post-emergence (bromoxynil) herbicide was evaluated for parthenium weed control in grain sorghum over two years. Pendimethalin or bromoxynil alone could only provide 54% and 63% control, whereas their sequential application provided 86% control of parthenium weed over the weedy treatment. The sorghum plants in pendimethalin followed by bromoxynil treatment had the highest leaf fresh weight per plant, plant dry biomass, plant height, and the number of heads among the herbicide treatments. Sorghum fresh forage yield, dry fodder yield, 1000-grain weight, and grain yield were highest in the weed-free treatment followed by the pendimethalin followed by (fb) bromoxynil treatment. Overall, the herbicide treatment performance was in an order of pendimethalin fb bromoxynil > bromoxynil > pendimethalin for weed control and sorghum yield improvement. These results suggest that pendimethalin followed by bromoxynil may provide acceptable control (>85%) of parthenium weed and may improve sorghum grain yield (up to 23%).