Effects of proteinase inhibitors and plant lectins on the adult alfalfa weevil (Coleoptera: Curculionidae)

The effects of selected proteinase inhibitors and plant lectins of alfalfa weevil, Hypera postica (Gyllenhal), adult foliar feeding and fecundity were significantly inhibited by the cysteine proteinase inhibitors E-64, pHMB, and leupeptin at a concentration of 0.1%. Pepstatin (aspartic inhibitor) at 0.5% and soybean Bowman-Birk trypsin inhibitor (serine) at 1.0% had no significant effect on adult foliar feeding, survival, or fecundity. Three of the four lectins tested significantly inhibited adult foliar feeding and fecundity at a concentration of 0.5%. A lectin from wheat and one from pea were the only two protein inhibitors tested to significantly inhibit adult survival. Results support a previous study that indicates the alfalfa weevil uses cysteine proteinases as major digestive enzymes. This study is one of few which demonstrates the effects of specific protein inhibitors on the adult stage of a foliar feeding insect species.