Chemical Characterization and Entomotoxicity of the Powders and Oil Extracts of Zanthoxylum zanthoxyloides (Lam.) and Anarcadium occidentale (L.) on Sitophilus oryzae (L.)

The rice weevil, Sitophilus oryzae is a cosmopolitan and economic pest of stored rice and other cereals. This study assessed the phytochemical composition and entomotoxic effect of powders and ethanolic oil extracts of Zanthoxylum zanthoxyloides and Anacardium occidentale on S. oryzae. Phytochemical screening and Gas chromatography/mass spectrometry (GC-MS) analysis were carried out on the oils of Z. zanthoxyloides and A. occidentale, while powders and oils of both plants were further assessed for their toxicity to S. oryzae at 1.0 g, 1.5 g, 2.0 g and 0.0625 ml, 0.125 ml, 0.50ml concentrations for both powders and oils respectively. Qualitative phytochemical analysis revealed the presence of flavonoids, phenolic compounds, and terpenoids, in the oils of both plants, with higher quantity of flavonoids (18%) detected in the oil of A. occidentale. The GC-MS analysis revealed the presence of 24 and 9 chemical compounds, among which Pellitorine;2,4 Decadienamide, N-isobutyl-,(E, E)-, a potent insecticidal compound, was identified in the oil of Z. zanthoxyloides. Mortality rates of S. oryzae treated with the powder and oil extracts increased with higher concentrations and duration. Powder of Z. zanthoxyloides displayed mortality rates ranging from 6.67 ± 6.67 % to 100.00± 0.00% within 24 to 96 hours, whereas A. occidentale powder exhibited rates from 6.67 ± 3.33% to 80.00 ± 15.28%. Similar trend was observed in the oil treatment. These findings highlight the potential of Z. zanthoxyloides and A. occidentale extracts as ecofriendly alternatives for S. oryzae control in stored grains.