Quantitative structure-activity studies of insect growth regulators: XVIII. Effects of substituents on the aromatic moiety of dibenzoylhydrazines on larvicidal activity against the Colorado potato beetleLeptinotarsa decemlineata

Larvicidal activity against the Colorado potato beetle Leptinotarsa decemlineata (Say) was measured for a series of N-tert-butyl-dibenzoylhydrazines having various substituents on the benzoyl (A-ring) moiety nearer to the tert-butyl group, with the other benzoyl (B-ring) moiety being unsubstituted. The effects of these substituent on the larvicidal activity were analyzed using classical quantitative structure-activity relationship (QSAR) procedures. The effects of substituents on the A-ring moiety on larvicidal activity were entirely different from those against the lepidopteran rice stem borer Chilo suppressalis (Walker) previously reported. Position-specific steric and hydrophobic effects, as well as certain substitution patterns, were likely to participate in modifying the larvicidal activity. The activity of para-substituted compounds was generally lower than that of un-, ortho- and meta-substituted compounds. Most multi-substituted compounds showed an activity equivalent to or lower than that of the unsubstituted compound. Among 46 compounds tested, the 2-sec-butoxy analogue was most potent against L decemlineata, although this compound had previously been shown to be only weakly active against C suppressalis.