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Aphids cause significant losses in many agricultural crops and in many cases cause repeated insecticide sprays, which increase the risk of resistance. Therefore, other alternatives are needed to control them. The toxic, anti-reproductive, and feeding deterrent effects of a mannose-binding lectin isolated from bulbs of Phycella australis Ravenna (Amaryllidaceae), named Phycella australis-agglutinin (PAA) was assayed on nymphs of the aphids Acyrthosiphon pisum Harris and Myzus persicae Sulzer fed with an artificial diet. After 72 h of PAA exposure, lethal concentration (LC50) values were 109 and 313 mu g mL(-1) for A. pisum and M. persicae, respectively, while LC90 values were 248 and 634 mu g mL(-1). Sub-lethal concentrations of PAA significantly reduced the aphid fecundity at a concentration of 80 mu g mL(-1). Only a total of 5.7 descendants per female were recorded for A. pisum (32% control progeny) and 12.4 for M. persicae (39% control progeny). Acyrthosiphon pisum was strongly deterred by PAA under choice conditions, as after 72 h exposed to 80 mu g PAA mL(-1) of diet, the feeding deterrent index was 0.91 for A. pisum and only 0.38 for M. persicae. In conclusion, the mannosebinding lectin isolated from bulbs of P. australis showed acute and chronical insecticidal activity against the pea and green peach aphids.