author(s)
Xin Chao Liu and Zhi Long Liu

abstract
During our mass screening program for new agrochemicals from the wild plants and Chinese medicinal herbs, essential oil of Ageratum conyzoides L. (Compositae)aerial parts at flowering stage exhibited strong larvicidal activity against the Asian tiger mosquito, Aedes albopictus. Essential oil of A. conyzoides aerial parts was obtained by hydrodistillation and analyzed by GC and GC-MS. A total of 32 components of the essential oil were identified and the principal compounds in the essential oil were precocene II (45.75%), precocene I (14.09%), and caryophyllene (12.13%) followed by germacrene D (4.18%) and caryophyllene oxide (4.06%). The essential oil had higher content (59.84%) of phenylpropanoids than monoterpenoids (3.70%) and sesquiternoids (33.01%). The essential oil of A. conyzoides aerial parts exhibited larvicidal activity against Ae. albopictus with an LC50 value of 61.22 μg/ml while the two major constituents, precocene I and precocene II had LC50 values of 43.55 μg/ml and 41.63 μg/ml, respectively. The present findings indicated that the essential oil of A. conyzoides aerial parts and two major constituents have potential for use in control of Ae. albopictus larvae and could be useful in search of newer, safer and more effective natural compounds as larvicides.