Journal of Phytopathology and Pest Management 4(3): 50-55, 2017 pISSN:2356-8577 eISSN: 2356-6507 Journal homepage: http://ppmj.net/ ∗ Corresponding author: Fereshteh Khorrami, E-mail: fkhorrami.khorrami20@yahoo.com 50 Copyright © 2017 Toxicity of some medicinal plant extracts to Pieris brassicae and combined effects with Proteus® against Brevicoryne brassicae Fereshteh Khorrami 1* , Asmar Soleymanzade 1 , Maryam Forouzan 2 1 Department of Plant Protection, Faculty of Agriculture, Urmia University, Urmia, Iran. 2 Plant Protection Research Department, West Azarbaijan Agricultural and Natural Resources Research Center, AREEO, Urmia, Iran. Abstract Keywords: cabbage pests, botanical insecticide, insecticidal activity, synergistic effect. Brevicoryne brassicae (Homoptera: Aphididae) is a considerable pest of cabbage. Pieris brassicae (Lepidoptera: Pieridae) exist in most countries where cabbages are cultivated. In this research, we were examined the synergistic interaction between Satureja hortensis L., Trachyspermum ammi I. Sprague, Ziziphora tenuior L., Cuminum cyminum L. and Foeniculum vulgare Mill. methanolic extracts with Proteus® against B. brassicae adults and toxicity of mentioned extracts to eggs and second instar larvae of P. brassicae under laboratory conditions. Probit analysis of extracts showed that the most effective extracts were ziziphora and savory which both exhibited LC50 values on adults of B. brassicae equivalent to 26.66 ppm. Methanolic extracts (except fennel) synergized the performance of Proteus®. Treated eggs of P. brassicae by methanolic extract of ziziphora elicited the lowest percentage of hatching rate. Studying of toxicity of extracts to 2 nd instar larvae of P. brassicae demonstrated that ammi, cumin and savory 5% methanolic extracts exhibited the highest efficacy to the pest.