Published online by Cambridge University Press: 12 June 2017
The persistence and effectiveness in pumpkin [Cucurbita moschata (Puch.) Poir.] weed control of several starch xanthide (SX) and commercial formulations of the ammonium (NH3) salt and methyl (CH3) ester of chloramben (3-amino-2,5-dichlorobenzoic acid) were studied in the laboratory and field. The soluble concentrate (SC) of chloramben NH3 salt and the emulsifiable concentrate (EC) of chloramben CH3 ester controlled weeds throughout the growing season on a silt loam soil. SC chloramben NH3 salt was not effective, and EC chloramben CH3 ester was inconsistent in weed control on sandy soil. Manipulation of the SX formulation produced products with slow, uniform release rates. The release rates (crosslinking reagent in parenthesis) rank as follows, from fastest to slowest: SX(Ca2+) CH3 ester = SX(H2O2) acid > SX(H2O2) CH3 ester > SX(Fe3+) acid > SX(Fe3+) CH3 ester. In trials on silt loam and sand, SX formulations did not control weeds better than EC chloramben CH3 ester.