Aphicidal Activity Of Major Alkaloids From Macleaya Cordata Against Wheat Aphids

Wheat aphids are ones of the most important pests of cereal crops, mainly controlled by chemicalpesticide. Aphid population could increase dramatically because of their short life cycle, high growingrate, over20generations in one wheat growth season, which calls for more pesticide, causing a series ofproblems, such as boosting resistance of aphids, pollution, and food safty. While botanical pesticidescan relieve mentioned problems. Therefore, researchers from domestic and abroad have devoted a lot todevelop new botanical pesticides, meanwhile, related studies and applications of botanical pesticideshave attracted intense attention in recent years. As reported Macleaya cordata extracts had insecticidalactivity to many pests, which indicated its potential to be developed into botanical pesticides, whilestudies on its aphicidal activity against wheat aphids were rarely published. Therefore, to find out itsaphicidal activity to wheat aphids is meaningful for the development of new types of botanicalpesticides.By dipping method, the aphicidal activities of M. cordata extract (MCE) and different fractionalkaloids, such as sanguinarine hydrochloride, chelerythrine hydrochloride and10%sanguinarine WPon three wheat aphid species, namely Sitobion avenae, Schizaphis graminum and Rhopalosiphum padi,were tested in the laboratory. With antifeedant method, the antifeedant activities of M. cordata alkaloidsagainst three wheat aphid species were tested. By adding to artificial diets method, effects ofsanguinarine hydrochloride and chelerythrine hydrochloride on survival rate of S. avenae alate adults.The results were as follows:Laboratory bioassay results showed that M. cordata extract and different fraction alkaloids, such assanguinarine hydrochloride, chelerythrine hydrochloride and10%sanguinarine WP had significantaphicidal activities against the three wheat aphid specieses, which increased with the increase ofconcentration and treatment time; At the dose of4g/L, after treating with for48h, the aphicidalactivities of treatments to wheat aphids could be sequenced by:10%sanguinarine WP＞chelerythrinehydrochloride＞MCE＞sanguinarine hydrochloride; After being treated with4g/L10%sanguinarine WP for48hours, corrected mortality rates of forth-instar alate nymphs of S. avenae, R.padi and S. graminum were up to65.17%,78.16%,86.34%, respectively, lethal concentration of50%(LC50) were2.5772g/L,0.8614g/L,0.4252g/L respectively, while those of alate adults were75.29%,93.59%,94.81%, LC50were0.1514g/L,0.3992g/L,0.4142g/L respectively; It indicated that S.graminum was more sensitive to all the extracts; After48hours’ treatment under the concentration of4g/L of MCE, sanguinarine hydrochloride, and chelerythrine hydrochloride, corrected mortality rates offorth-instar alate nymphs of S. graminum were60.24%,58.45%,60.24%, respectively, while those ofthe alate adults were81.42%,62.74%and69.53%, respectively.Results of antifeedant methods showed that MCE, sanguinarine hydrochloride and chelerythrinehydrochloride showed antifeedant effect to both alate adults and forth-instar alate nymphs. The effect differed with the change of time and concentration without significant linear relationship with them;When the concertration of MCE is over0.5g/L, after a treatment of24h, antifeedant rates of alate adultswere all above50%, it suggested that it showed good antifeedant activity.Results of artificial diets method showed that sanguinarine hydrochloride and chelerythrinehydrochloride made significant effect on survival of alate adults of S. avenae; After feeding the artificialdiets containing with sanguinarine hydrochloride at the dose of125μg/mL for12h,24h,36h,48h,and72h, survival rates of adults were60.96%,40.78%,17.35%,3.48%,1.96%, respectively, while forthe chelerythrine hydrochloride were65.00%,49.63%,17.13%,3.61%and0%, respectively.To sum up, M. cordata alkaloids had aphicidal and antifeedant activities on all wheat aphidspecieses, while sanguinarine hydrochloride and chelerythrine hydrochloride made effects on thesurvival rates of the alate adults of S. avenae. Therefore, it indicated that M. cordata alkaloids hadprospects to be developed as aphicide. This research provides theoretical basis for the further researchand development of botanical pesticide.