Efficacy of some microbial control agents and inorganic insecticides against red flour beetle Tribolium castaneum and confused flour beetle Tribolium confusum (Coleoptera: Tenebrionidae)


Abstract: The efficacy of three fungal pathogens, Isaria fumosorosea, Nomuraea rileyi and Verticillium lecanii alone and their combination with natural diatomaceous earth (DE) and silicagel-O-500 and silica-O-750 evaluated against Tribolium castaneum and Tribolium confusum. Results showed that modified diatoms with Calcium hydroxide (Ca-DE) and modified diatoms with Sodium hydroxide (Na-DE) were the most effective treatments against the two tested insects and achieved the highest mortality percentages. T. castaneum achieved the highest tolerant to tested DEs. Cab-O-Sil-750 gave highest mortality against T. castaneum reached to 89, 50 and 12% at concentrations 1, 0.5 and 0.25 g/kg wheat, respectively. The fungus I. fumosorosea was the most effective alone against T. castaneum. Ca-DE and Na-DE treatments strongly enhanced the potency of the tested fungi I. fumosorosea and N. rileyi. Results showed that T. castaneum was susceptible to N. rileyi. Larvae of T. castaneum were more tolerant to V. lecanii alone. In most cases, DE combinations with tested fungi had synergistic effects, while in T. castaneum modified diatoms with aluminium hydroxide (Al-DE) decreased the efficacy of V. lecanii. Both silica gel and diatoms protected wheat better. The egg production was highly suppressed by combination of Ca-DE followed by Na-DE with tested fungi in comparison to untreated control. The combination of Ca-DE/I. fumosorosea strongly suppressed the number of deposited eggs of T. castaneum (87.5 ± 9.6 eggs/female) in comparison to untreated control (277.0 ± 5.9 eggs/female). The most effective DEs modifications were Ca-DE and Na-DE with insecticidal, repellency or ovicidal effects against T. castaneum and had synergistic effects on the potency of tested fungi.

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