Uptake and Phytotoxicity of Tebuthiuron

Abstract

Differences in the phytotoxicity of tebuthiuron ( N -[5-(1,1-dimethylethyl)-1,3,4-thiadiazol-2-yl]- N,N ′-dimehtylurea) to nine plant species were observed on the basis of calculated GR 50 values. Japanese brome ( Bromus japonicus Thunb.) with a GR 50 value of 0.016 ppmw was the most susceptible and corn ( Zea mays L. ‘Gold Rush’) with a GR 50 value of 0.436 ppmw the least susceptible. There was some growth suppression with foliar application but primary activity on all species was attributed to root uptake. The most significant translocation of labeled tebuthiuron was to the tops of common ragweed ( Ambrosia artemisiifolia L.) plants treated through the nutrient solution where 24.5% of the total amount recovered was detected after 24 h. Only 7.3% of the total amount recovered was detected in the top of rye ( Secale cereale L. ‘Elbon’) plants with the same treatment. With both species, more than 90% of the radioactivity recovered following foliar treatments was still in the treated leaf after 24 h. Less than 5.5% of the recovered activity for both species was in the tops, less than 3% in the roots, and less than 1.5% was in the nutrient solution.