Control of Stored-Product Beetles with Combinations of Protein-Rich Pea Flour and Parasitoids

Abstract

Protein-rich 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 the rusty grain beetle, Cryptolestes ferrugineus (Stephens). This study found that protein-rich pea flour was not toxic to, and did not reduce the offspring of, Anisopteromalus calandrae (Howard), a parasitoid of S. oryzae, nor did it reduce offspring of Cephalonomia waterstoni (Gahan), a parasitoid of C. ferrugineus. Protein-rich pea flour was also not repellent to A. calandrae. Small-scale and large-scale tests of a combination of protein-rich pea flour and parasitoids were conducted in 2-liter jars and in barrels containing 330 kg wheat. A larger population of A. calandrae was found at a high host infestation rate (24 adults/kg for 25 d), but the parasitoid did not become established at middle and low host infestation rates (2.4; 0.24 adults/kg for 25 d). The combinations of protein-rich pea flour and parasitoids reduced populations of S. oryzae in both tests. Additional effects of protein-rich pea flour and parasitoids were found in the large-scale test. Releasing parasitoids alone reduced the populations of S. oryzae by 46% and C. ferrugineus by 49%. Treating wheat with 0.04 or 0.1% protein-rich pea flour reduced the population of S. oryzae by 26 and 79% and C. ferrugineus by 27 and 43%, respectively. Combining parasitoids with 0.04 or 0.1% protein-rich pea flour reduced S. oryzae populations by 76 and 98% and C. ferrugineus populations by 42 and 75%, respectively. At the end of the large-scale experiment, grain treated with protein-rich pea flour alone or in combination with parasitoids had better grain quality than the untreated controls.