The discovery of eco-friendly plant-based insecticides is currently booming in research with an attempt to replace synthetic chemical insecticides causing tremendous adverse effects. The present work studied the insecticidal potential of ginger, an important medicinal plant. Four crude extracts from Zingiber officinale rhizomes were evaluated for their contact toxicity against second instars of Spodoptera litura, Spodoptera exigua and Spodoptera frugiperda using the topical application. The hexane extract exhibited the strongest toxicity to S. exigua with the LD50 of 9.92 and 8.40 µg/larva at 24 and 48 h posttreatment, respectively, followed by S. frugiperda. Comparative toxicity of the most abundant secondary metabolites from the hexane extract, gingerols and shogaols, against both insects concluded that 8-shogaol (5) was identified as the most active compound against S. frugiperda with the LD50 of 7.68 and 3.96 µg/larva at 24 and 48 h posttreatment, respectively.
Keywords: Spodoptera spp; Zingiber officinale Roscoe; contact toxicity; gingerols; insecticidal activity; shogaols.