Kalata B1 shown to possess potent insecticidal activity.
Helicoverpa punctigera larvae were raised on artificial diets based on haricot beans. The test diet was supplemented with the kalata B1 peptide (0.825Â¬Â¬Âµmol/g of diet). The control diet contained casein in place of the inhibitor. Twenty neonates were added to each diet, and mortality was recorded every 2Â¬days. Weight gain was recorded at the sixth day and every second day thereafter. The larvae were reared in 1.5-ml microfuge tubes (one larva/tube) until day eight, when they were transferred to individual plastic containers with lids [Solo (Urbana, IL) plastic portion cups, 28Â¬ml]. Larvae were fed initially small amounts of diet (40Â¬mg) that were replaced as required to provide a continuous supply. The larvae were kept in a temperature controlled room at 25Â¬Â¬Â±Â¬1Â¬C, 16:8 (light/dark).
Purified kalata B1 was incorporated into an artificial diet and fed to larvae for 16Â¬days postemergence. Kalata B1 had a significant effect on the development of larvae compared with larvae on a diet free of kalata. No mortality was observed in the first 6Â¬days, although 50% failed to survive past day sixteen. After 16Â¬days, none of the 12Â¬survivors had progressed past the first instar stage of development and weighed 3.3Â¬mg (Â¬Â±1.1 mg standard deviation). Most larvae on the control diet, however, had achieved fifth instar, and the average mass was 284Â¬mg (Â¬Â±96.1 mg standard deviation).