Herbicide Resistance Mechanism in Phalaris minor and its Consequences on Management Strategies

Herbicide resistance occurs with the repeated use of a specific herbicide for control of weed species that contain some plants in the population with a resistant gene. The resistant type will increase with each use of the herbicide over time because the gene pool in the field will shift from susceptible to resistant. This shift is permanent assuming that the resistant type plants have no fitness penalty and resistance is not due to genetic alterations (target site mutation). Use of one herbicide from a group with one mode of action may quickly evolve resistance to other herbicides with the same mode of action as has been reported with many weed species. Evolved multiple resistance in P. minor to herbicides of different modes of action in India, Israel, Mexico, South Africa and USA suggests that no single herbicide will be able to control P. minor for long and we need to swiftly change our strategy than P. minor to arrest its proliferation and economic loss. An integrated approach using knowledge of its biology, improved agronomic practices, cultural, chemical and mechanical control methods, sanitation, quarantine and farmers' awareness are indispensable components for successful management of P. minor.