Insecticidal Activity of Essential Oils Against Cabbage AphidBrevicoryne brassicae

The essential oils of Lavandula augustifola, Rosmarinus officinalis, Nepeta cataria and Origanum majorana applied by fumigation were highly toxic to the cabbage aphids (Brevicoryne brassicae). The essential oils of Nepeta cataria and Lavandula augustifola were the most toxic with LD50s of 1.42μl/l and 3.35μl/l and LD90s of 14.06μl/l and 7.65 μl/l after 24 hours, respectively. Oils extracted from Origanum majorana and Rosmarinus officinalis were less toxic with LD50s of 7.45μl/l and 15.85μl/l and LD90s of 11.64 μl/l and 25.95 μl/l. While the essential oils of N. cataria and R. officinalis caused some discoloration and dessication to the leaves of cabbage plants, damage occurred only at a higher dose of 25 μl/l after an exposure period of 48 hours. Therefore, essential oils of three of these plants have good potential for the control of greenhouse pests such as cabbage aphids at doses that can kill up to 90% of the pest.