Antimetabolic effects of plant lectins towards nymphal stages of the planthoppers Tarophagous proserpina and Nilaparvata lugens

Taro Colocasia esculenta (L. Schott) and rice (Oryza sativa L.) form a majo r part of the staple diet of pacific islanders. Pest constraints hamper the sustainability of taro and rice production in the Pacific region. Insect f eeding trials were conducted in vitro to determine the effects of plant lec tins against planthopper pests of taro and rice. Lectins were incorporated into artificial diet at 0.1% (w/v) level. The lectins Galanthus nivalis agg lutinin (GNA) and concanavalin A (Con A) showed significant antimetabolic e ffects towards third instar nymphs of taro planthopper (Tarophagous proserp ina Kirkaldy) whilst Pisum sativum agglutinin (PSA) showed no significant e ffects toward the insect. Psophocarpus tetragonolobus agglutinin (PTA) show ed significant antimetabolic effects towards third instar nymphs of rice br own planthopper (Nilaparvata lugens Stal). PTA also reduced honeydew excret ion levels of rice brown planthopper, over a 24-hour period, demonstrating antifeedant properties of the protein.