Published online by Cambridge University Press: 12 June 2017
Fifty-day-old jimsonweeds (Datura stramonium L.) were susceptible and tomatoes (Lycopersicon esculentum Mill.) tolerant to soil-applied metribuzin [4-amino-6-tert-butyl-3-(methylthio)-as-triazin-5(4H)-one] at 0.25 and 0.50 kg/ha. Spray applications of 0.50 kg/ha metribuzin to jimsonweed foliage, or to both foliage and soil, reduced jimsonweed height growth 39 and 66%, respectively; whereas, tomato height was reduced 57 and 50% by the two placement methods, respectively. Metribuzin applied to a basal leaf appeared to move both basipetally and acropetally in jimsonweed, but only basipetally in tomato. Metribuzin applied to tomato leaves reduced growth 28% more when leaves had been abraded than when not abraded. Differential translocation appeared to be a major factor in selectivity. Directed sprays of metribuzin at 0.3 and 0.6 kg/ha on the lower 75% of jimsonweed leaves provided control in the field without injury to tomatoes.