Bioassay of Some Indigenous Entomopathogens for Controlling , Olivier in Saudi Arabia.

<b>Background and Objective:</b> The red palm weevil is a dangerous date palm pests that cannot be controlled with chemical pesticides only. As a result of the justified concerns of the negative use of synthetic insecticides on human health and the environment. So on, candidate eco-friendly micro-organisms isolated from KSA agri-ecosystems were evaluated in controlling RPW. <b>Materials and Methods:</b> Some indigenous entomopathogenic fungi and bacteria were isolated from naturally infected RPW larvae and adults and evaluated as alternative control methods. <b>Results:</b> The infection of RPW larvae with entomopathogenic fungi and bacteria under natural conditions was higher than in adults. <i>Beauveria bassiana </i>was the most prevalent followed by <i>Aspergillus </i>sp., <i>Metarhizium anisopliae</i>, <i>Mucor</i> sp., <i>Cladosporium chlorocephalum</i>. In contrast, both <i>Bacillus</i> <i>thuringiensis</i> and <i>Bacillus popilliae</i> formed 73.9 and 26.1%, respectively. From the 7th day, mortalities (%) increased gradually and recorded the highest mortalities with 21st days after treatment and recorded 93.33, 66.70, 53.36, 46.69 and 60.00% when treated with <i>B. bassiana</i>, <i>M. anisopliae</i>, <i>C. chlorosphalum</i>, <i>Mucor</i> sp. and <i>Aspergillus</i> sp., respectively. <b>Conclusion:</b> Although there was evidence indicating midgut damage and feeding inhibition among larvae that survived the treatments, instead of lower activity of <i>B. thuringiensis</i> against <i>R. ferrugineus</i> immature stages may refer to that, Both species of <i>Bacillus</i> were more virulent as the days 15-21 post-treatment.