Benazolin and Admixtures for Common Cocklebur (Xanthium pensylvanicum) and Prickly Sida (Sida spinosa) Control in Soybeans (Glycine max)

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Abstract
Benazolin (4-chloro-2-oxobenzothiazolin-3-ylacetic acid) formulated as the dimethylamine salt was evaluated for common cocklebur (Xanthium pensylvanicumWallr.) and prickly sida (Sida spinosaL.) control in soybeans [Glycine max(L.) Merr.] between 1977 and 1979. Benazolin was applied alone or in admixtures with acifluorfen {5-[2-chloro-4-(trifluoromethyl)phenoxy]-2-nitrobenzoic acid}, bentazon [3-isopropyl-1H-2,1,3-benzothiadiazin-4 (3H)-one 2,2-dioxide], dinoseb (2-sec-butyl-4,6-dinitrophenol) plus naptalam (N-1-naphthylphthalamic acid), and 2,4-DB [4-(2,4-dichlorophenoxy)butyric acid] over-the-top of soybeans {V3 to V12 [V(N); vegetative stage with “N” nodes on the main stem beginning with the unifoliolate node]}. Benazolin effectively controlled common cocklebur at rates of 0.2 and 0.4 kg/ha. Soybean tolerance was acceptable even with a repeat application of 0.4 kg/ha. Early-season (July) control was less than late season (August) because it took 2 to 3 weeks for benazolin to kill common cocklebur. Prickly sida control was poor with benazolin even at 0.6 kg/ha. Soybean tolerance and seed yields were higher when soybeans were treated with admixtures of benazolin plus bentazon than with benazolin alone. Antagonism was observed with this admixture for prickly sida and late-season common cocklebur control. Antagonism was eliminated with ratios of benazolin to bentazon of 1 to 3 applied in a single application or a 1 to 1.5 ratio repeated.