molecules Article Evaluation of Aphicidal Effect of Essential Oils and Their Synergistic Effect against Myzus persicae (Sulzer) (Hemiptera: Aphididae) Qasim Ahmed 1,† , Manjree Agarwal 2,† , Ruaa Al-Obaidi 3, Penghao Wang 2,* and Yonglin Ren 2,* 1 Agricultural Engineering Sciences, University of Baghdad, Al-Jadriya Campus, Baghdad 10071, Iraq;
[email protected] 2 College of Science, Health, Engineering and Education, Murdoch University, South Street, Murdoch, WA 6150, Australia;
[email protected] 3 Pharmacy College, Mustansiriyah University, Al-Qadisyia, Baghdad 10052, Iraq;
[email protected] * Correspondence:
[email protected] (P.W.);
[email protected] (Y.R.) † These authors contributed equally to this paper. Abstract: The insecticidal activities of essential oils obtained from black pepper, eucalyptus, rose- mary, and tea tree and their binary combinations were investigated against the green peach aphid, Myzus persicae (Aphididae: Hemiptera), under laboratory and glasshouse conditions. All the tested essential oils significantly reduced and controlled the green peach aphid population and caused higher mortality. In this study, black pepper and tea tree pure essential oils were found to be an effective insecticide, with 80% mortality when used through contact application. However, for combinations of essential oils from black pepper + tea tree (BT) and rosemary + tea tree (RT) tested Citation: Ahmed, Q.; Agarwal, M.; as contact treatment, the mortality was 98.33%. The essential oil combinations exhibited synergistic Al-Obaidi, R.; Wang, P.; Ren, Y. and additive interactions for insecticidal activities. The combination of black pepper + tea tree, Evaluation of Aphicidal Effect of eucalyptus + tea tree (ET), and tea tree + rosemary showed enhanced activity, with synergy rates Essential Oils and Their Synergistic of 3.24, 2.65, and 2.74, respectively.