Uptake, translocation and fate of sulfoxaflor in three plants: Cabbage (Brassica oleracea), pepper (Capsicum annuum) and cotton (Gossypium hirsutum)

The insecticide sulfoxaflor being developed by Dow AgroSciences is a broad-spectrum insect control agent with excellent efficacy on sap feeding pests including aphids, whiteflies, hoppers and lygus. Sulfoxaflor controls insects by activation of nicotinic acetyl choline (nAChR) receptors in a way that is novel compared to other nAChR agonists such as the neonicotinoids. Sulfoxaflor showed excellent activity after foliar application suggesting that uptake and movement in plants was not a barrier to activity. Insecticides with activity on sap feeding insects such as azinphos-methyl, chlorantraniliprole and fipronil are primarily xylem mobile, so it was hypothesized that sulfoxaflor would also exhibit translocation via the xylem. This paper highlights the uptake, translocation and metabolism of 14C-sulfoxaflor on 2 to 3 leaf cabbage, pepper and cotton and also on 5 leaf pepper. Leaf application of compound was used to determine the type of translocation, xylem verses phloem. Stem application, as illustrated by phosphor images, was used to understand the extent of translocation. Sulfoxaflor was determined to be xylem translocated by demonstrating classical movement profiles indicative of distribution with the transpiration stream. Little to no movement (< 0.2%) was observed out of the treated leaf in all plant species tested. We conclude that sulfoxaflor moves in planta strictly in the xylem. Metabolism in 5 leaf pepper plants was not so rapid as to jeopardize activity but by 30 days after application no parent material was left in the plant. Metabolism involved oxidative cleavage followed by conjugation with glucose and malonate. Stem application also indicated wide distribution throughout the plant. Sulfoxafor has the right match of plant uptake, xylem translocation and metabolic stability to achieve excellent sap feeding insect control.