Efficacy of Pea Protein and Combinations of Pea Protein and Wasps Against Stored-Grain Insects in Large Scale Tests

Protein-enriched pea flour is toxic and repellent to three major stored grain pests, the rice weevil, Sitophilus oryzae (L.), the red flour beetle, Tribolium castaneum (Herbst) and rusty grain beetle, Cryptolestes ferrugineus (Stephens). A unique and valuable aspect of the protein-enriched pea flour is that it is not toxic several parasitoids that are associated with two of these insect pests. These parasitoids include Anisopteromalus calandrae (Hymenoptera: Pteromalidae), a parasitoid of S. oryzae, and Cephalonomia waterstoni (Hymenoptera: Bethylidae), a parasitoid of C. ferrugineus. Two large scale tests, including one test in combination with the parasitoids, were conducted to evaluate the effectiveness of the pea flour as a grain protectant. A two-month, 30-tonne-granary trial with barley was conducted in 6 bins, each filled with 11 tonnes of barley. Bins had full-floor aeration, hence insects could leave or enter the grain mass. Results showed that treating all the barley during loading with 0.1% of pea protein had a similar effect as treating the barley in only the top half of the granary with 0.5% of pea protein. Compared with control bins, the treatments with protein-enriched pea flour reduced the size of S. oryzae populations by more than 90%, and those of Cryptolestes ferrugineus and T. castaneum by more than 70%. A five-month, 330-kg-barrel test with wheat was set up to test the effectiveness of the combination of protein-enriched pea flour with parasitoids against S. oryzae and C. ferrugineus. The parasitoid A. calandrae and C. waterstoni reduced the mean number of S. oryzae by about 70% but the reduction was not significant because of high variability in the controls. Combinations of parasitoids and pea flour at 0.1% significantly reduced the S. oryzae population by 99.8%. For unknown reasons, the populations of C. ferrugineus did not become established in the barrel tests. As a result, we could make no conclusions concerning the effectiveness of the combination of parasitoids and protein-enriched pea flour against this major pest.