Many plant lectins have high anti-insect potential. Although the effects of most lectins are only moderately influencing development or population growth of the insect, some lectins have strong insecticidal properties. In addition, some studies report a deterrent activity towards feeding and oviposition behavior. Transmission of plant lectins to the next trophic level has been investigated for several tritrophic interactions. Effects of lectins with different sugar specificities can vary substantially with the insect species under investigation and with the experimental setup. Lectin binding in the insect is an essential step in exerting a toxic effect. Attempts have been made to study the interactions of lectins in several insect tissues and to identify lectin-binding receptors. Ingested lectins generally bind to parts of the insect gut. Furthermore, some lectins such as the Galanthus nivalus agglutinin (GNA) cross the gut epithelium into the hemolymph and other tissues. Recently, several candidate lectinbinding receptors have been isolated from midgut extracts. To date little is known about the exact mechanism for insecticidal activity of plant lectins. However, insect glycobiology is an emerging research field and the recent Grant sponsor: Fund for Scientific Research-Flanders, Brussels; Grant number: 3G016306.Correspondence to: Guy Smagghe, Ghent University, Coupure Links 653, B-9000 Ghent, Belgium. E-mail: guy.smagghe@ugent.be Vol. 73, No. 4, 193-212 (2010 ARCHIVES OF INSECT BIOCHEMISTRY AND PHYSIOLOGY,

In view of the increasing use of plant proteins as valuable alternatives to chemical insecticides, the Susceptibility of pea aphids, acyrthosiphon pisitin (Harris) (Hemiptera: Aphididae), to three purified mannose-binding plant lectins was determined in an artificial-diet bioassay. The insecticidal activities of a new lectin, APA (Allium porrum L. (Liliaceae) agglutinin) from garden leek, were compared with those of GNA (Galanthus nivalis L. (Liliaceac) agglutinin) from snowdrop and ASA (Allium sativum L. agglutinin) from cultivated garlic. GNA and ASA showed acute toxicity to first-instar nymphs; LC50 values for GNA and ASA were 350 and 700 mu g/mL, respectively. With APA, mortality was scored only at high doses. In chronic experiments, however, lower closes significantly reduced survival and fecundity of adults (P < 0.05). Aphids fed a diet containing APA at 100, 500, and 750 pg/mL showed a significant delay in reaching adulthood and no aphids survived beyond 19 days of development. The data support the potential application of APA in the integrated management of insect pests