Environmental Modification of Seedling Alfalfa,Medicago sativa, Tolerance to Bromoxynil

Seedling alfalfa exhibited increased phytotoxicity from bromoxynil when applications were made with temperatures greater than 28 C both in controlled environments and in the field. Treatments applied in the morning were more phytotoxic than treatments made in the late afternoon. In laboratory experiments, inhibition of oxygen evolution occurred within 1 h after treatment. The amount of permanent damage sustained was dependent on the rate of bromoxynil and the length of time the alfalfa was exposed to light or darkness immediately after spraying. Bromoxynil treatments in cool weather and/or in the late afternoon should minimize injury to the crop.