Translocation of Bentazon in Soybeans and Common Cocklebur

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Abstract
Translocation of 14C-labeled and toxicity of nonradiolabeled bentazon [3-isopropyl-1H-2,1,3-benzothiadiazin-(4)3H-one 2,2-dioxide] was determined for common cocklebur (Xanthium pensylvanicum Wallr.) and soybeans [Glycine max (L.) Merr.]. Significantly greater 14C-movement and herbicide toxicity occurred in common cocklebur growing in wet soil at field capacity than in dry soil near the wilting point. In common cocklebur there was a trend toward greater bentazon toxicity and 14C-translocation at high temperature (35 C) and high relative humidity (RH) (96%) than at low temperature (25 C) and low RH (35%). ‘Lee 68’ soybeans were injured less than 10% by bentazon under any environmental condition of this study. Translocation of 14C was primarily acropetal in both common cocklebur and soybeans. Herbicide movement was affected by leaf maturity with the greatest movement of 14C resulting from 14C-bentazon applied to the most mature common cocklebur leaf near the base of the shoot and to soybeans at the youngest fully expanded leaf near the apex of the shoot. Bentazon was more toxic and 14C translocation was greater in the soybean cultivar ‘Hurrelbrink’ than ‘Hill’ or Hill X Hurrelbrink cross.