Management of Resistant Phalaris minor in Wheat

Phalaris minor is a serious grass weed of wheat in India and has evolved resistance against isoproturon. A considerable research effort has made to develop alternative weed management practices that can prevent development of herbicide resistance. The present investigation was carried out to assess the resistance against fenoxaprop and clodinafop; to evaluate the performance of new herbicides pinoxaden and a ready mix formulation of sulfosulfuron and metsulfuron against resistant P.minor biotypes and to investigate the mechanism of fenoxaprop detoxification in P.minor. The results revealed that cross resistance has evolved against fenoxaprop and clodinafop. The resistance biotypes could be partially controlled by pinoxaden a new ACCase inhibitor. However these could be completely managed by ready mix formulation of sulfosulfuron plus metsulfuron without any adverse effects on wheat. The reversal of cross resistance to fenoxaprop could not be observed by using malathion an inhibitor of cytochrome P-450 mono-oxygenase. This study is indicative of the fact that detoxification mechanism was not involved in imparting cross resistance. If at all it was involved only partially.