Evaluation of Substituted Oxime Ethers for Growth Regulatory Activity against Spodoptera litura (F.)

Insect growth regulatory activity (IGR) of fifty-two substituted oxime ethers was evaluated against an important polyphagous lepidopteran crop pest, Spodoptera litura (F.). A number of compounds produced symptoms comparable to exogenously applied juvenile hormone. Maximum IGR activity was exhibited by 4’-(2,6,6-trimethyl-2-cyclohexen-1-yl)-3’-buten-2’(E)-ketoxime-N-O-alkyl ether with an ED₅₀ (morphological) of 40 μg g⁻¹ body weight, compared to 20 μg g⁻¹ for JH III. Two more compounds namely 4’-(2,6,6-trimethyl-2-cyclohexen-1-yl)-3’-buten-2’(Z)-ketoxime-N-O-methyl propyl ether (ED₅₀ 192 μg g⁻¹) and 4’-(2,6,6-trimethyl-1-cyclohexen-1-yl)-3’-buten-2’(E)-ketoxime-N-O-pentyl ether (ED₅₀ 380 μg g⁻¹) showed considerable IGR activity, whereas 4’-(2,6,6-trimethy1-2-cyclohexen-1-yl)-3’-buten-2’(E)-ketoxime-N-O-pentyl ether was found to be toxic to the larvae (ED₅₀ 268 μg g⁻¹). Three compounds used in this study were also synergised by piperonyl butoxide (PBO). The synergistic ratios were found in the range of 1.33–4.605. The ovicidal activity of the oxime ethers is not significant.