Heliyon (Feb 2025)
Chemical composition and insecticidal potential of botanical fractionation extracts for the management of Sitophilus zeamais Motschulsky, 1855 (Coleoptera: Curculionidae) in stored maize
Abstract
The weevil Sitophilus zeamais (Motschulsky, 1855) (Coleoptera: Curculionidae) is a destructive pest of stored maize, particularly in warm and humid tropical regions. The objective of this study was to analyze the chemical composition and evaluate the insecticidal potential of fractionated extracts of Eucalyptus globulus, Tagetes minuta and Annona squamosa used as natural alternatives to synthetic insecticides in the management of S. zeamais. Fractionated extracts were obtained by macerating and soaking E. globulus leaves, whole T. minuta plants and A. squmosa seeds using hexane, chloroform, and methanol as extraction solvents. Experiment tests were carried out at different doses (5, 10, and 15 g/kg) on adult S. zeamais to investigate adult mortality rate, progeny inhibition rate, repellent effect, fumigation effects, and effects on grain weight loss. Mortality of adult S. zeamais was observed after application at 24, 48, and 98 h. All fractions exhibited insecticidal activity, which increased with higher doses and longer post treatment periods. At a dose of 15 g/kg, the hexane, chloroform and methanol fractions of E. globulus caused a mortality rate of 100 % at 48 h of exposure and an inhibition rate of more than 100 % in progeny production. All fractions at lower doses (5 g/kg) showed a lower mortality of S. zeamais, which was significantly less than that of Actellin 2 % dust used as a positive control. The composition of bioactive extracts was analyzed using a gas chromatography-mass spectrometry (GC-MS) apparatus. GC-MS results of the major components of the E. globulus extract were aromandendrene (24.83 %), globulol (10.33 %), heneicosane (15.56 %), hexadecanoic acid, and methyl ester (7.50 %). For A. squamosa, there was nonadecane (2.35 %), hexadecanoic acid methyl (16.06), heneicosane (25.42 %), 9, 12-octadecadienoic acid (23.35 %), and 9-octadecenoic acid (26.466 %), and methyl stearate (2.55 %). The major components identified from the fractionated extract of Tagetes minuta were methyl 10-trans, linolenic acid (62.79 %), hexadecanoic acid, methyl ester (19.10 %) and heneicosane (5.78 %), and methyl stearate (5.46 %). E. globulus leaves and their constituent compounds have potential for the development of natural insecticides or fumigants for the control of maize weevils in stored grains. The findings can contribute to developing eco-friendly, safer and more sustainable alternatives to synthetic chemical insecticides.
