Insecticidal and Antimicrobial Potential of the Volatile Oils of the Aerial Parts of Teucrium ramosissimumand Thymus hirtus subsp. algeriensisGrowing in the South-West of Tunisia

AbstractThe aim of this report was to investigate the possible lethal effect of Thymusand Teucriumessential oils against insects. Antimicrobial activity was evaluated by the disc diffusion assay. Relative repellency, fumigation and plant lethality on certain pest species were tested. A higher concentration of thyme (9.95 µL/cm2) essential oil showed the greatest repellent effect against Tribolium confusumand Supella longipalpa. Exposure of pests to 2 µL thyme essential oil (EO) /l air resulted in 100 % mortality in 24 h. Thyme and Teucrium EO induced dose-response mortality of T. confusumlarvae with LC50values ⁣⁣of 45.22 and 38.10 µL/l air, respectively. Maximum lethality was recorded after 24 h and 48 h of exposure to the essence of T. algeriensis. Moreover, a total repellency effect was detected within 1 h of experiment at a concentration of 9.95 µL/cm2. Furthermore, complete lethality (100 %) of the nymph and adult of S. longipalpa(1˂ LT50˂6 h), T. confusum(LT50˂7 h) and the larvae of Blaps nefrauensis(1˂ LT50˂3 h) were observed. Additionally, thymol (0.3% w/w) was shown to induce moderate repellency and fumigant effect against studied insects. Overall, thyme and teucrium essential oils can be alternative botanical pesticides for these insects. But further experiments are needed to justify the insecticidal effect of essential oils used directly on T. confusumin cereal stores. As well, the experimental procedure using low doses of essential oil used for insecticidal potency should be repeated with high doses.