EFFECT OF THIFENSULFURON CONCENTRATION AND DROPLET SIZE ON PHYTOTOXICITY, ABSORPTION, AND TRANSLOCATION IN PEA (PISUM-SATIVUM)

Greenhouse experiments were conducted to evaluate phytotoxicity, absor ption, and translocation of thifensulfuron when applied to pea at diff erent 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-1 for droplet diameters of 110, 155, 300, and 450 mum, respect ively. The C-14-thifensulfuron absorption as percent of applied increa sed twofold, whereas translocation decreased 36 % as herbicide concent ration increased from 18 to 146 mg L-1 in 980-mum droplets. Small drop lets (50 mum) that dried to particles before contact with leaves did n ot damage pea plants. However, under dew conditions, dry particles dam aged peas to a similar degree as liquid droplets. We concluded that sm all and concentrated droplets of thifensulfuron can damage peas more t han large and diluted droplets as a result of increased herbicide abso rption.