In this study, the toxicity and mechanism of action of concanavalin A (ConA) in the grain aphid (Sitobion avenae) were studied. Feeding assays with S. avenae on an artificial diet containing different concentrations of ConA demonstrated an inhibitory effect on fecundity as well as high mortality caused by this lectin. ConA also increased the pre-reproductive period and the development time and reduced the intrinsic rate of natural increase. Moreover, an extract of the gut of treated S. avenae demonstrated an increase in caspase-3 activity together with DNA fragmentation, suggesting that ConA can induce the apoptotic pathway. These results suggest that ConA may be detrimental in insect gut tissues and the interaction of ConA with epithelial cells may be responsible for the observed insecticidal effects.

The toxicity effect of Concanavalin A ( Canavalia ensiformis lectin, ConA) to bird cherry-oat aphid, Rhopalosiphum padi L. (Hemiptera: Aphididae), was investigated in the laboratory by using artificial diets containing ConA concentrations. Bird cherry-oat aphid performance was affected by the presence of Con A in artificial diets. The lectin added into the liquid diet increased the prereproductive period, mortality, and the average time of generation development ( T ) and decreased fecundity and the intrinsic rate of natural increase ( rm ). In attempt to unravel the mode of action of ConA, the interaction of the lectin with insect gut and the effect of ConA on feeding behavior were investigated. Extract of gut of treated grain aphid demonstrated DNA fragmentation, and this was accompanied with an increase in caspase 3 activity. Moreover, addition of ConA to the sucrose–agarose gels reduced salivation and passive ingestion of fluids from the gel. The results indicate that the insecticidal activity of ConA on R. padi may involve effects on death of the gut epithelial cells and effects on feeding behavior. This can be employed to create plants that are resistant to aphids.

In the current work, the toxicity and mechanism of phytohaemagglutinin (PHA), lectin isolated from the kidney bean (Phaseolus vulgaris) to the grain aphid (Sitobion avenae F.) were studied. When S. avenae was fed an artificial diet containing the lectin PHA, toxicity assays indicated that fecundity decreased, the pre-reproductive period and generation time were prolonged, and mortality increased. To elucidate the mode of action of PHA, the interaction between the lectin and the insect gut was investigated. Interestingly, DNA fragmentation was observed in extract of gut of treated grain aphid, and this was accompanied by an increase in caspase-3 activity. Results indicate that the detrimental activity of PHA on S. avenae may involve effects on death of the gut epithelial cells.