Abstract: Insecticidal activities and chemical constituents of essential oils from alien invasive plants Solidago canadensis and Wedelia trilobata were investigated. The results showed that the two plant essential oils exhibited fumigant and contact activities against three stored-product insect pests. The fumigant LC₅₀ values of essential oil of S. canadensis against Tribolium castaneum, Sitophilus zeamais and Callosobruchus chinensis were 7.72 μL/L, 237.05 μL/L and 43.28 μL/L, respectively, and the contact LD₅₀ values were 2.71×10^-4 μL/adult, 1.40×10^-5 μL/adult and 2.35×10^-5 μL/adult, respectively. The fumigant LC₅₀ values of essential oil of W. trilobata against T. castaneum, S. zeamais and C. chinensis were 187.06 μL/L, 156.73 μL/L and 0.93 μL/L, respectively, and the contact LD₅₀ values were 7.52×10^-5 μL/adult, 2.84×10^-5 μL/adult and 1.18×10^-5 μL/adult, respectively. The two plant essential oils also inhibited the population of C. chinensis, with the inhibition rates being 57.30%-82.12% for essential oil of S. canadensis and 37.63%-67.86% for W. trilobata at concentrations of 1-3 μL/g. Fifty eight compounds from S. canadensis oil and fifty two compounds from W. trilobata oil were identified using GC/MS technique. The most principal component of S. canadensis oil was germacrene D (49.43%), and the principal components of W. trilobata oil were 1 R-α-pinene (28.79%), D-limonene (23.70%) and α-phellandrene (10.80%).

Key words: Solidago canadensis L., Wedelia trilobata (L.) Hitchc., essential oil, insecticidal activities, chemical constituents