| Stored-product insects cause billions of dollars of losses every year throughout the world. Synthetic insecticides are widely used to control stored-product insects. However, their use is decreasing, because of concerns about insecticide residues in grain, damage to the environment, worker safety, insecticide resistance and increasing costs. To reduce the use of synthetic insecticides, many natural products have been investigated for the control of stored-product insects. Laboratory studies indicated that protein-rich pea flour, a food additive, was repellant, toxic and reduced offspring of three common stored-product insects, Sitophilus oryzae (L.) (rice weevil), Cryptolestes ferrugineus (Stephens) (rusty grain beetle) and Tribolium castaneum (Herbst) (red flour beetle). Sitophilus oryzae was the most sensitive species, followed by C. ferrugineus and T. castaneum. Insects held on wheat and barley showed similar sensitivities to protein-rich pea flour. Higher doses were required to control insects held on maize. Protein-rich pea flour was more toxic at high temperature and low moisture. Although protein-rich pea flour reduced the penetration of package material by S. oryzae , it did not prevent insects from entering perforated packaging.;A granary trial conducted in six 30-tonne bins and each filled with 11 tonnes of barley showed that fewer insects moved into, and more insects moved out of the barley treated with protein-rich pea flour. Treating the entire gain mass with 0.1% protein-rich pea flour had a similar effect to treating the top-half with 0.5% protein-rich pea flour. Sitophilus oryzae populations were reduced by approximate 90%. The populations of C. ferrugineus and T. castaneum were reduced by 50--70% in both treatments. Similar reductions were seen in offspring adults.;Unlike other insecticides, protein-rich pea flour was neither repellent and nor toxic to Anisopteromalus calandrae (Howard), a parasitoid of S. oryzae, or Cephalonomia waterstoni (Gahan), a parasitoid of C. ferrugineus. Protein-rich pea flour did not increase the mortality of the two parasitic wasps. It did not reduce the searching ability of parasitoids, and nor did it reduce the production of parasitoid offspring. A large-scale trial combining 0.1% pea protein with parasitoids showed that the population of S. oryzae was reduced by 98% and that of C. ferrugineus by 75%, which is greater than treatments of parasitoids alone (46% for S. oryzae, 50% for C. ferrugineus).;Neem and protein-rich pea flour acted synergistically against T. castaneum. Malathion and protein-rich pea flour acted synergistically against S. oryzae. In contrast, combination of protein-rich pea flour with diatomaceous earth or with pyrethrum acted additively against S. oryzae. All other combinations acted antagonistically. A mixed function oxidase inhibitor, piperonyl butoxide, increased the effectiveness of a pea extract as an antifeedant, and increased the mortality of S. oryzae. However, a gluthion-S-transferase inhibitor, diethy meleate, did not enhance the antifeedant effect or toxicity of the pea extract.;A large volume of gas was observed in the midgut of S. oryzae fed on flour disks treated with protein-rich pea flour, pea extract or pea peptide. Vital staining with fluorescent dyes, calcein AM and propidium iodide, showed that the tissue of the midgut of the insects was damaged by the pea peptides. |
