Adult food and species type influence the nutritional physiology and tolerance of two flour beetles to the extract of Dennettia tripetala (G. Baker)

Abstract

Tribolium castaneum (Herbst) and Tribolium confusum (Jacquelin du Val) are common and damaging pests of stored grain flours in several homes and flour mill industries worldwide. This study examines how food, species, concentration, and exposure time affect the susceptibility and nutritional physiology of T. castaneum and T. confusum when exposed to partially purified methanolic fruit extract of Dennettia tripetala (G. Baker) and two of its major active compounds (linalool and 2-phenylnitroethane). Gas chromatography–mass spectrometry was used to evaluate the chemical profile of the partially purified plant extract. Thirty-two compounds were found in the plant, including established insecticidal and insectifuge compounds such as linalool, cis-vaccenic acid, 2-phenylnitroethane, and linoleic acid, among others. The interactions among the factors have a differential impact on the susceptibility and nutritional indices of both Tribolium species to D. tripetala, linalool and 2-phenylnitroethane. According to LC₅₀ values, linalool and 2-phenylnitroethane were the most and least toxic to both beetles, respectively. With increasing extract concentrations, all nutritional indices except feeding deterrence decreased. Relative to controls, linalool and 2-phenylnitroethane evoked the highest and least reduction, respectively, in beetles' nutritional indices. Treated corn discs deterred both species over treated wheat discs, regardless of insecticide type. T. castaneum had a higher overall food consumption than T. confusum. Regardless of insecticide type, the relative growth rate was higher in T. confusum and T. castaneum fed with treated corn and wheat discs, respectively. D. tripetala extract, linalool, and 2-phenylnitroethane showed higher post-ingestion toxicity to T. castaneum than T. confusum. This study emphasises the importance of certain intrinsic factors, like beetles' species and cereal food types, when managing Tribolium species with plant-based insecticides. The various data obtained from this study will help researchers and pesticide manufacturers formulate effective biopesticides from linalool and 2-phenylnitroethane to control Tribolium species on corn and wheat flours.