The toxicity and bioactivity of climbing wedelia powder and essential oil against maize weevil
2021
Mongkol, Wongsawas | Darika, Bunphan | Phirayot, Khaengkhan | Ruchuon, Wanna | Waranyoo, Kaewduangta
Many types of powders and essential oils derived from plants are used as traditional protection for stored products against insect pests. They are relatively non-toxic to mammals and they meet the criteria for reduced risk pesticides. The toxicity and bioactivity of the powder and essential oil of the climbing wedelia, Wedelia trilobata (L.) A.S. Hitchcock, were determined against maize weevil, Sitophilus zeamais Motschulsky. The powder and essential oil were obtained from the aerial parts of W. trilobata and tested for their toxicity, as well as insecticidal and residual activities, against S. zeamais. The LC⁵⁰ value of the W. trilobata powder to S. zeamais was 582.86 g/kg grain within 72 hours, while the essential oil was 1,146.19 μL/L air within 24 hours. Mixing powder with grain at a dosage of 80 g/kg grain killed S. zeamais at 7.50% after 12 days of exposure and reduced the progeny of S. zeamais by 89.96%. After fumigation, concentrations of 150, 200 and 250 μL/L air of W. trilobata essential oil showed 2.50%, 5.00% and 12.50% of adult mortalities in S. zeamais after 24 hours of exposure, with 81.97%, 83.07% and 97.65% reductions in progeny, respectively. The W. trilobata powder and essential oil showed efficacy in the protection against the newly emerged progeny of S. zeamais (>80%). The W. trilobata essential oil exhibited moderate to strong residual activities. The results suggest that the powder and essential oil of W. trilobata may be effectively used in the management of S. zeamais populations in grain storage.
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