Evaluation and Management of Fenoxaprop-P-ethyl Resistance in Phalaris minor Retz

Abstract

Widespread herbicide resistance in Phalaris minor Retz., is a major bottleneck towards sustainability of wheat-based cropping system in Pakistan and many other Asian countries. A dose–response assay was conducted for confirmation of resistance in surveyed populations. Optimization of herbicide mixtures to control P. minor in wheat was done under wirehouse conditions. To manage P. minor efficacy of herbicide mixtures in integartion with crop row spacings and allelopathic crop mulches were investigated at the Agronomic Research Area, Department of Agronomy, University of Agriculture, Faisalabad over two consecutive growing seasons during winter 2014-15 and 2015-16. Most of the collected populations were resistant to fenoxaprop-P-ethyl. Resistance levels were 2.13-6.50. The tested herbicide mixtures both at 75 and 100% of the recommended dose of each mixture component provided effective control of resistant P. minor without any phytotocity on wheat. The herbicide mixtures provided consistent, effective control of P. minor under field conditions especially in 11.25 cm rows compared to in 22.50 cm wheat row spacing. Integrated use of allelopathic crop mulches and herbicide mixtures was effective to control of P. minor in wheat. They consistently enhanced the wheat yield by 23-39% and 24-35% during 2014-15 and 2015-16, respectively. The confirmation of ACCase inhibitor resistance as the first case of herbicide resistance in Pakistan leads us to discourage use of ACCase inhibitor herbicides alone. However, herbicide mixtures both at 75 and 100% of the recommended dose are suggested to manage this weed for sustainable wheat production in the surveyed cropping systems. Integration of herbicide mixtures with narrow row spacing of wheat and allelopathic mulches can help address herbicide-resistant P. minor in wheat fields.