First results on potential insecticidal activity of plant powders of invasive alien plants against rice weevil under laboratory conditions

Abstract: The effectiveness of eleven different plant powders from eight invasive alien plant species was evaluated on rice weevil (Sitophilus oryzae) regarding 2-4 weeks old adults’ mortality. Wood ash from Norway spruce (Picea abies) was used as positive control. We have prepared plant powders from leaves of stinkworth, Bohemian knotweed, Japanese knotweed, tree of heaven, and false indigo; from Canada goldenrod, giant goldenrod, and staghorn sumac we have prepared plant powders from leaves and flowers. Plant powders/wood ash were applied at two different concentrations (2.5 and 5% w%). Mortality of the adults was evaluated after 7, 14, and 21 days. Research was performed at three temperatures (15, 20, and 25 °C) and 55% relative humidity. Based on the results of our survey we conclude that mortality of rice weevil adults was influenced by treatment, dose of plant powder/wood ash, and day of exposure. Highest mortality of rice weevil adults was achieved in positive control, meanwhile mortality in treatments with plant powders did not exceeded 20%. The highest mortality was detected in vial, where the beetles were exposed to false indigo.For this reason, we suggest mixing tested plant powders with other inert dusts (like DE, wood ash) for improving the efficacy.