Acute, synergistic and antagonistic effects of some aromatic compounds on the Spodoptera littoralis Boisd. (Lep., Noctuidae) larvae

The efficacy of 30 aromatic compounds and their mutual binary combinations was tested for acute toxicity against the larvae Spodoptera littoralis. Based on a comparison of the lethal doses, the thymol, carvacrol and trans-anethole were selected as the most effective, and LD50 was estimated for them at 9, 15 and 18 mu g/larva, respectively, and LD90 at 28, 35 and 41 mu g/larva, respectively. In total, 435 binary combinations were tested, of which 135 combinations showed a significant synergic effect, while 150 combinations showed a significant antagonistic effect on mortality. Only 6 substances were identified as being able to create a synergic effect with more than 20 substances: gamma-terpinene, limonene, p-cymene, trans-anethole, borneol and camphor. L-carvone and gallic acid created an antagonistic effect with the highest frequency. The highest synergic effect was achieved for the combination of camphor and borneol, with the place of expected mortality estimated at 4.8% and mortality at 88.6%. In order to verify the synergic interaction of camphor and borneol, the effectiveness in terms of acute toxicity for S. littoralis larvae was determined for three fundamental mixing ratios of the substances. Significantly different LD50 values (88 and 134 mu g/larva, respectively) were found for camphor/borneol mixtures prepared in the ratios 2:1 and 1:1, respectively. The information learned can thus be used in the development of new botanical insecticides based on EOs, and particularly in the creation of formulations. (C) 2014 Elsevier B.V. All rights reserved.