Antagonistic Responses with Combinations of Carbamate and Growth Regulator Herbicides

Antagonistic responses were noted on sorghum ( Sorghum vulgare pers.) and giant foxtail ( Setaria faberii Herrm.) using preemergence combinations of (2,4-dichlorophenoxy)acetic acid (2,4-D) and the carbamates S -ethyl dipropylthiocarbamate (EPTC), isopropyl m -chlorocarbanilate (chlorpropham), and 2-chloroallyl diethyldithiocarbamate (CDEC). Combinations of EPTC and (2,4,5-trichlorophenoxy)acetic acid (2,4,5-T) or 3,6-dichloro- o -anisic acid (dicamba) gave similar results. Effects of these combinations were mainly additive on four dicotyledonous species. Combinations of 2,4-D and N -1-naphthylphthalamic acid (naptalam) also were antagonistic on sorghum and giant foxtail but were additive on the remaining species. Eight other herbicide combinations were mainly additive on all six species.