Ovicidal and Larvicidal Effects of Selected Plant-Based Biopesticides on <i>Tuta absoluta</i> (Lepidoptera: Gelechiidae)

The tomato leafminer, Tuta absoluta Meyrick (Lepidoptera: Gelechiidae), is a worldwide invasive pest of tomatoes (Solanum lycopersicum L.) that reached West Africa in 2010. Synthetic insecticides remain the most widely used method of control, but several biological alternatives are being developed. In this work, we evaluated nine biopesticides available on the West African market for their ability to control T. absoluta. Using standard leaf or egg dip bioassay methodology, we compared both the ovicidal and the larvicidal activity of these biopesticides at various concentrations of active ingredients. We found that, for each biopesticide tested, the larval lethal concentrations (LC) (8.2–41.14 ml/L) to be lower than those necessary to stop egg hatching (26.7–409.7 ml/L). Two products (Bangr-Kièta [BK]; Bangr-Pougo [BP], formulated in powder), both based on Azadirachta indica A. Jussieu fruit and leaf extracts and Khaya senegalensis (Desrousseaux) A. Jussieu bark extract, showed high efficacy in reducing egg hatchability at their recommended doses, with a calculated control failure likelihood (CFL) reaching 0%. These two products, together with a third one (BP) based on Mitracarpus scaber Zuccarini and K. senegalensis extracts, also showed the strongest larvicidal effects (CFL = 0%). All other tested biological insecticides showed significant efficiency but were found to be less effective at their recommended doses. Because the leafminer has developed resistance to most of the synthetic insecticide available on the market, we recommend that West African tomato producers are encouraged to use the most efficient biological products available