Effects of essential oils of Origanum vulgare L. (Fam. Labiatee), Pelargonium odoratissimum L. (Fam. Geraniaceae) and Syzygium aromaticum L. (Fam. Mirtaceae) on mortality of Aphis gossypii Glover (Homoptera: Aphidiidae) in laboratory

The cotton aphid, Aphis gossypii Glover (Homoptera: Aphidiidae), is a cosmopolitan and highly polyphagous species causing serious economic damage to numerous plants including Cucurbitaceae. The use of synthetic insecticides represent the main method of control of this aphid, often resulting in resistance to all the major insecticide group. The use of natural products, such as essential oils (EOs), has increased in recent years because they have advantages in reduction of this resistance. Within this research area, we have implement and evaluate the applications of EOs that aim at reinforcing knowledge on the control of this aphid. We investigated the topical application of the EOs of Origanum vulgare L. (oregano), Pelargonium odoratissimum L. (cloves) and Syzygium aromaticum L. (geranium bourbon) by means the Potter tower on 1st instar nymphs under laboratory conditions. In our results, mortality response to EOs tested was dose-dependent and depending on the time from the treatment. It is remarkable that already after 24 hours of exposure to treatments, all three EOs caused mortality. Highest mortality was detected after 48 at doses of 1200 μl/l with values of 52%, 67% and 69% for clove, geranium and oregano, respectively. The probit analysis after 24 hours revealed that the lowest DL50 was detected for oregano (562.34 μl/l), followed by geranium (707.95 μl/l) and clove (954.99 μl/l) EOs. The results highlight a potential use of these EOs in the pest control being less toxic to the plants unlike chemical-based insecticides.