The effect of water stress on the efficacy of diclofop-methyl and CGA 184′927+S on wild oat (Avena fatua)

Abstract

The response of wild oat (Avena fatua) to diclofop-methyl and CGA 184′927+S under conditions of water stress was assessed in a pot experiment. Treatments with 0, 8, 16 and 24% polyethylene glycol (PEG 6000) were used to impose water stress. The water stress treatments were initiated when the plants reached the two-leaf stage and continued for seven days prior to and two days after the herbicides were applied. Leaf extension rate was the most sensitive plant parameter to water stress and was decreased by all water stress treatments. Stomatal diffusive resistance of wild oat. Leaves was increased significantly by the 16 and 24% PEG treatments. These water stress treatments caused a reduction in the response of wild oat to diclofopmethyl as illustrated by a continuation of the leaf extension rate during the first week after spraying. The survival and seedhead production of diclofop-methyl-sprayed plants were greatest at the highest water stress level (24% PEG). Water stress did not affect the efficacy of CGA 184′927+S on wild oat. The leaf expansion of plants sprayed with this herbicide stopped within four days after spraying and all plants died within 35 days, irrespective of the water stress level imposed.