A Cucumber Bioassay Test for the Soil Residues of Certain Herbicides

Abstract

A bioassay standard curve injury rating, using cucumbers (Cucumis sativusL.) as the indicator plant, was developed for quantitatively determining soil residues of 5-bromo-3-sec-butyl-6-methyluracil (bromacil), 6-dichloro-o-anisic acid (dicamba), 3(3,4-dichlorophenyl)-1,1-dimethylurea (diuron), (2,3,6-trichlorophenyl)-acetic acid (fenac), 4-amino-3,5,6-trichloropicolinic acid (picloram), and 2,4-bis(isopropylamino)-6-methoxy-s-triazine (prometone). The herbicide concentrations ranged from 0.001 to 2.187 ppmw. The presence of all the herbicides could be detected at 0.009 ppmw and the herbicides killed cucumbers at 2.187 ppmw. Cucumbers could be used to effectively measure a greater concentration range of fenac than the other herbicides. A highly significant negative correlation existed between injury rating and fresh plant weight. However, concentrations of the herbicides were more easily detected by a visual injury rating on abnormal growth characteristics than by fresh plant weight.