GROWTH AND YIELD OF PEA (PISUM-SATIVUM L) AND LENTIL (LENS-CULINARIS L) SPRAYED WITH LOW RATES OF SULFONYLUREA AND PHENOXY HERBICIDES

Drift of sulfonylurea and phenoxy herbicides from spring cereal fields to nearby spring pea and lentil crops was simulated by spraying pea a nd lentil with 2,4-D or the 2:1 commercial mixture of thifensulfuron a nd tribenuron at rates of 0, 0.33, 1, 3.3, or 10% of the use rates (X) for spring cereal crops approximately 3 and 5 wk after planting pea a nd lentil, 2,4-D had minimal inhibitory effects on both crops at all r ates tested, Lentil was slightly more sensitive than pea to 10% X 2,4- D, Thifensulfuron:tribenuron had no effect on either crop at rates les s than 3.3% X, Two weeks after application of thifensulfuron:tribenuro n, 10% X, and to a lesser degree 3.3% X rates, caused newly emerged le aves to become chlorotic, reducing chlorophyll content 25 to 50%, Thes e treatments also reduced net photosynthesis by 37% and reduced or hal ted growth of the main stern, Early formation of eaves was reduced, th us tripling light penetration through the canopy, Five to six weeks af ter application, 10% X thifensulfuron:tribenuron had, in some treatmen ts, more than tripled branching in pea, more than quadrupled branching in lentil, and reduced biomass as much as 42%, Flowering and maturity were delayed, Plants recovered from stunting by thifensulfuron:triben uron to varying degrees depending on environmental conditions, and fin al seed yield generally was reduced less than 25%. In controlled green house experiments, rate response to thifensulfuron generally was simil ar to that observed in field experiments, Pea was stunted less at 30 C than at 10 C, whereas lentil was affected similarly at these temperat ures, Overall, visual symptoms from thifensulfuron:tribenuron exposure were more pronounced in pea than in lentil and were detectable at lev els substantially lower than those that affected final seed yields.