RESPONSE OF ONION (Allium cepa) TO OXYFLUORFEN DURING EARLY SEEDLING DEVELOPMENT

Abstract

The response of onion (Allium cepa L.) to postemergence applications of oxyfluorfen during early seedling development was measured in growth room experiments. Tolerance to oxyfluorfen increased more than 70-fold from the late loop to the two fully developed leaf stage. Field and growth room experiments were also conducted to determine the relationship of spray retention and epicuticular wax on the tolerance of onion seedlings to the herbicide. In general, there was a progressive decrease in spray retention and a corresponding increase in epicuticular wax per unit dry weight as plant age increased. Spray retention in the field was approximately twice as great as in the growth room. The amount of epicuticular wax on the leaf surfaces of the onions was about equivalent under the two growing conditions. A significant decrease in epicuticular wax per unit dry weight between the late one-leaf and late two-leaf stages occurred under both field and growth room conditions, while tolerance to the herbicide continued to increase during the same period.Key words: Onions, oxyfluorfen, ED50, spray retention, epicuticular wax