Established Forage Alfalfa (Medicago sativa) Tolerates Glyphosate and SC-0224 Applied to Control Dodder (Cuscutaspp.)

Abstract

Established alfalfa treated with glyphosate at 75 or 150 g ae/ha (rates known to control dodder) during the vegetative or bud stage showed symptoms of narrowed leaves and mildly chlorotic new growth, and yield of one cutting of alfalfa usually was reduced by 10 to 20%. Glyphosate, applied in the vegetative stage, affected the treated foliage more than postharvest regrowth. Applied at bud stage, the regrowth that followed harvest of treated foliage was affected more. Symptoms and effect on yield were greater at 300 g ae/ha, but alfalfa always recovered. Applying glyphosate at 75 or 150 g ae/ha in each of two or three sequential cuttings showed no cumulative effect. Glyphosate and SC-0224 had similar effects on alfalfa and suppressed alfalfa much less than would a severe infestation of dodder.