Synergistic Effects of Combining Three Commercial Bioproducts Against (Meyrick) Larvae (Lepidoptera: Gelechiidae).

<b>Background and Objective:</b> The use of entomopathogenic agents for crop pest management is a viable alternative to synthetic chemical pesticides. <i>Beauveria bassiana</i> (Bals.) and <i>Metarhizium anisopliae</i> (Metsch.) are fungi considered the most promising extensively widely applied bio-control agents in protecting a wide range of economic crops. Fungal toxins are thought to play a crucial part in the pathogenicity process during insect infestation. The bioinsecticides' synergy could help to control the invasive pest more safely and effectively. <b>Materials and Methods:</b> Suspensions of Beauveroz (<i>Beauveria</i> <i>bassiana</i>) and Metarhoz-P (<i>Metarhizium anisopliae</i>), were evaluated as to their virulence against <i>T.</i> <i>absoluta</i> larvae at 3 different doses. As a comparison, Abamectin was utilized as a positive control, while water was used as a negative control. <b>Results:</b> All the commercial compounds caused significant mortality among <i>T.</i> <i>absoluta</i> larvae, with approximately 52% mortality after 5 days of the treatment. Over 5 days, mortality of <i>T.</i> <i>absoluta</i> larvae when exposed to a combined treatment of <i>B.</i> <i>bassiana</i>, <i>M.</i> <i>anisopliae</i> and Abamectin reached 92%. The results under field conditions, showed significant differences (p<0.001) among these products while adding the surfactants increased the mortality larvae. Combined treatments of these 3 commercial compounds showed a synergistic effect acceded the effect obtained using each compound alone. Bio-pesticides, <i>B.</i> <i>bassiana</i> and <i>M.</i> <i>anisopliae</i> formulations caused mortality rates among <i>T.</i> <i>absoluta</i> larvae similar to the Abamectin treatment. <b>Conclusion:</b> Observations indicated that both fungus candidates and Abamectin proved effective against <i>T. absoluta</i> larvae. The combined use showed a high potentiality indicating a positive synergistic effect.