Parasitism Rates and Foraging Behavior of Anisopteromalus calandrae (Howard) (Hymenoptera: Pteromalidae) A Parasitoid of some Stored Grain Insects

This study studied the effect of the parasitoid Anisopteromalus calandrae against three stored grain pests Callosobruchus maculatus (Fabr.) (Coleoptera: Chrysomelidae: Bruchinae), Cowpea weevil, Sitophilus granarius (Linnaeus) (Coleoptera Curculionidae) Wheat weevil, and Rhyzopertha dominica (Fab.) (Coleoptera: Bostrichidae) Lesser grain borer under natural storage conditions during two years (2023–2024). Monthly sampling from grain stores in Talkha, revealed significant seasonal variations in parasitism rates, with peak activity occurring in summer months. A. calandrae showed highest efficacy against C. maculatus (72.8% parasitism in August 2023), (71.2% in 2024), followed by R. dominica (70.8% in July 2023, decreased to 60.8% in 2024) and S. granarius (65.2% in August 2023, decreased to 51.2% in 2024). Laboratory experiments demonstrated that parasitoid foraging behavior was strongly influenced by host grain type, with maximum searching rates observed on cowpea for C. maculatus (0.500), sweet corn for S. granarius (0.396), and wheat for R. dominica (0.434). Mutual interference values followed similar patterns, indicating grain-specific host preferences. Density-dependent experiments showed parasitism rates increased linearly with parasitoid numbers, reaching 79.4% for C. maculatus on cowpea on the highest density (9 females). Comparative analysis revealed C. maculatus as the most susceptible host, particularly when reared on cowpea. These results suggest that A. calandrae can be effectively deployed for biological control in grain storage systems, with optimal timing (summer months) and grain-specific release strategies significantly enhancing pest suppression. The study provides critical data for developing integrated pest management protocols that reduce reliance on chemical pesticides while maintaining grain quality during storage.