Effect of Thifensulfuron Concentration and Droplet Size on Phytotoxicity, Absorption, and Translocation in Pea (Pisum sativum)

Abstract

Greenhouse experiments were conducted to evaluate phytotoxicity, absorption, and translocation of thifensulfuron when applied to pea at different rates, droplet sizes, and as dry particles. Thifensulfuron rates that reduced shoot dry weight by 25% were 0.46, 0.59, 0.98, and 1.21 g ai ha-1for droplet diameters of 110, 155, 300, and 450 μm, respectively. The14C-thifensulfuron absorption as percent of applied increased twofold, whereas translocation decreased 36% as herbicide concentration increased from 18 to 146 mg L-1in 980-μm droplets. Small droplets (50 μm) that dried to particles before contact with leaves did not damage pea plants. However, under dew conditions, dry particles damaged peas to a similar degree as liquid droplets. We concluded that small and concentrated droplets of thifensulfuron can damage peas more than large and diluted droplets as a result of increased herbicide absorption.