Ammonium Sulfate Enhancement of Picloram Activity and Absorption

Picloram (4-amino-3,5,6-trichloropicolinic acid) herbicidal activity on seedlings of guava (Psidium guajava L.), strawberry guava (Psidium cattleianum Sabine), and dwarf beans (Phaseolus vulgaris L. ‘Bountiful’) was increased by adding ammonium sulfate to the spray solution. Picloram activity tended to increase with increasing ammonium sulfate concentration up to 10% (w/v), but by the end of each experiment ammonium sulfate concentrations above 0.5% were generally equally effective. The absorption of 14C-picloram by strawberry guava leaves was increased about five-fold by 0.5% and 10% ammonium sulfate. There was about four times more 14C-picloram in the upper stem and attached leaves when ammonium sulfate was added than with picloram alone. Ammonium sulfate at 0.5% increased picloram absorption by four-fold in guava, but there was no increase in the amount of picloram translocated acropetally. Picloram absorption by dwarf beans, measured by difference between the amount of picloram applied and the amount recovered, was increased by 0.5% and 10% ammonium sulfate by a similar magnitude as on guava species.