Growth inhibitory and lethal effects of some botanical insecticides and potential synergy by dillapiol in Spodoptera litura (Fab.) (Lepidoptera : Noctuidae)

Synergistic effects of dillapiol with several botanical insecticides and pl ant extracts were investigated using leaf disc bioassays on early 4(th) ins tar larvae of the tobacco cutworm, Spodoptera litura. Neem, rotenone, and t oosendanin were synergized by dillapiol in the first 24 h of the bioassay ( period of direct exposure). However, in the subsequent 72 h following expos ure to the combinations of botanical insecticides with dillapiol, the syner gy did not persist. Dillapiol appeared to antagonize the growth inhibitory (sublethal) effects of neem, Melia volkensii, and Annona squamosa extracts over this time period, but mortality of larvae exposed to neem, rotenone, t oosendanin, and Annona squamosa was significantly enhanced by coadministrat ion of dillapiol. Dillapiol at 0.05 % was especially synergistic with neem (0.5 %) and pyrethrum (0.1 %).