Abstract: The effects of alkaloids from Sophora alopecuroides on oviposition of Plagiodera versicolora, an important insect pest attacking poplar trees, were studied using leaves of young poplar as oviposition substrates. Results showed that different alkaloids from S. alopecuroides had different toxicity to the P. versicolora adults, causing different effects on oviposition behavior. In selective feeding condition, 5 mg·mL^-1 of sophocarpine, matrine, aloperine and total alkaloids strongly inhibited oviposition and the inhibition rates were 61.2%,61.3%,46.3% and 53.2% respectively, while the same dose of sophoradine and oxymatrine had limited effects on oviposition inhibition (inhibition rates were 6.4% and 5.3%, respectively). Matrine in 5 mg·mL^-1 also had a high oviposition repellent rate (54%) while the other alkaloids monomers did not show significant differences in the repellent rate of oviposition. In non-choice test, the inhibition rates of oviposition, when treated (long-term, 12 days) with the total alkaloids, aloperine, oxymatrine and sophoradine, were higher than those in choice test, reaching to 82.2%, 74.4%, 55.6% and 33.6%, respectively. When treated with oxymatrine, aloperine or sophoradine, female P. versicolora preferred depositing eggs on non-alkaloids treated leaves over alkaloids treated leaves. Although clutch size was not affected, female egg production was significantly inhibited after being treated with these low toxic alkaloids. The fecundity and clutch sizes deposited by female P. versicolora were also affected significantly when treated with stronger toxic alkaloids such as sophoramine or sophocarpine.

Key words: Sophora alopecuroides, alkaloids, Plagiodera versicolora, oviposition behavior, repellent, inhibition