Toxicity of Cytisine against the Mustard Aphid Lipaphis erysimi Kaltenbach (Homoptera: Aphididae) and Its Effect on Esterases

The toxicity of cytisine from Sophora alopecuroides (L.) (Papilionaceae) against the mustard aphid Lipaphis erysimi (Kaltenbach) and its effect on esterase activities were studied. The efficacy of cytisine against aphids was higher than that of anabasine and nicotine, two botanical aphidicides from Nicotiana tabacum and Anabasis aphylla. The median lethal concentrations of the three alkaloids against the apterous adult were 432.59, 648.70, and 1090.65 mg/L, respectively, at 48 h of pest treatment using the cage-dip method. A second set of experiments utilized colorimetry to measure total esterase and carboxylesterase activity from 4th-instar larvae of the diamondback moth, Plutella xylostella (L.), which were pretreated with the alkaloids. Cytisine inhibited esterase and carboxylesterase activities in this species; moreover, there was an inverse relationship between alkaloid concentration and esterase activity.