The Effect of Adjuvant Mepiquat and Spray Volume on the Adverse Effect of Dust on Non-Selective Contact Herbicides’ Efficacy on Winter Wild Oat

The dust deposited on the foliage of weeds can have an adverse effect on the efficacy of herbicides, thus this effect should be eliminated somehow. In this greenhouse study conducting at Bu-Ali Sina University in 2018, the response of fresh : dry weight ratio of winter wild oat to the 6 doses of oxyfluorfen (0, 28.8, 60, 120, 240, and 480 g a.i. ha-1), paraquat (0, 36, 75 , 150, 300, and 600 g a.i. ha-1), and glufosinate (0, 60, 125, 250, 500, and 1000 g a.i. ha-1) sprayed with 240, 480, or 240 L ha-1 plus mepiquat at 50 g ha-1 under conditions of 0 and 20 Kg dust ha-1 were investigated. In the absence of dust, the addition of mepiquat to oxyfluorfen and paraquat spray solutions did not have a significant effect on their efficacy but the addition of it to glufosinate spray solution gave a significant negative effect on its efficacy. In the presence of dust, the addition of mepiquat to oxyfluorfen spray solution did not have a significant effect on its efficacy but the addition of it to glufosinate spray solution has 6-fold negative effect on its efficacy. While, the addition of mepiquat to paraquat spray solution had a positive effect on its efficacy and increased the efficacy by 62.07%. Whether dust was applied or not, increasing spray volume from 240 to 480 L ha-1 resulted in an improvement in the efficacy of all herbicides to desiccate the foliage of winter wild oat.