This study was conducted to determine the toxicity to adult Myzus persicae (Sulzer) and Aphis gossypii Glover of 88 plant essential oils and six experimental spray formulations containing bitter orange or marjoram oil was examined using the vapor-phase mortality and spray bioassays. Results were compared with those of two conventional insecticides deltamethrin and dichlorvos. As judged by 24 h LC50 values, bitter orange oil (0.0212 and 0.0192 mg/cm3) was the most active material, followed by marjoram, celeryseed, and cypress oils (0.0239-0.0508 and 0.0209-0.0542 mg/cm3). These essential oils were significantly less toxic than dichlorvos, respectively. These essential oils were consistently more toxic to adult M. persicae in closed versus open containers, indicating that toxicity was achieved mainly through the action of vapor. Bitter orange oil and marjoram oil applied as 1% spray provided complete mortality toward two aphid species adults. Reasonable aphid control in greenhouses can be achieved by a spray formulation containing the 1% oil as potential contact-action fumigant.

• Haribalan Perumalsamy(Department of Agricultural Biotechnology, Seoul National University)
• Xue Wang(Department of Agricultural Biotechnology, Seoul National University)
• Hye Min Shin(WCU Biomodulation, Seoul National University)
• Jun-Ran Kim(Department of Crop Life Safety, National Academy of Agricultural Science, Rural Development Administration)
• Byeoung-Ryeol Choi(Department of Crop Life Safety, National Academy of Agricultural Science, Rural Development Administration)
• Soon-Il Kim(Nareso Co., Ltd., Bio Venture Valley, Suwon 441–853, Gyeonggi,)
• Young-Joon Ahn(Department of Agricultural Biotechnology, Seoul National University)