Response of the macadamia seed weevil Kuschelorhynchus macadamiae (Coleoptera: Curculionidae) to Metarhizium anisopliae and Beauveria bassiana in laboratory bioassays

• Published in: Journal of invertebrate pathology 2020-07, Vol.174, p.107437, Article 107437
• Main Authors: Khun, Kim Khuy, Ash, Gavin J., Stevens, Mark M., Huwer, Ruth K., Wilson, Bree A.L.
• Format: Article
• Language: English
• Subjects: Beauveria; Kuschelorhynchus; Macadamia; Metarhizium; Pathogenicity; Virulence
• ISSN: 0022-2011; 1096-0805
• DOI: 10.1016/j.jip.2020.107437

[Display omitted] •Both Metarhizium anisopliae and Beauveria bassiana are highly pathogenic.•Indigenous isolates performed as well as commercially available entomopathogens.•Entomopathogens in the future can be integrated into IPM programs. Macadamia seed weevil, Kuschelorhynchus macadamiae Jennings and Oberprieler, is a major pest of macadamia in eastern Australia, causing yield losses of up to 15%. Current control methods involve two applications of acephate per season but more recently have moved to a single application of indoxacarb, combined with the collection and destruction of fallen nuts that contain developing larvae. As a first step towards reducing the dependence of the industry on synthetic insecticides, we tested six isolates of M. anisopliae, six isolates of B. bassiana and one commercial B. bassiana product (Velifer® biological insecticide) against adult macadamia seed weevil under laboratory conditions. All isolates were pathogenic against adult weevils with M. anisopliae accession ECS1/BRIP 70272 and B. bassiana accession B27/BRIP 70267 causing 97.5% and 92.5% mortality 12 days after being treated at 1 × 107 conidia/mL. Isolates ECS1/BRIP 70272 and B27/BRIP 70267 had the shortest LT50 values of 5.13 days and 5.37 days respectively. The median lethal concentrations (LC50) for ECS1/BRIP 70272 and B27/BRIP 70267 were 1.48 × 105 and 1.65 × 105 conidia/mL respectively. Results of this study indicate that M. anisopliae accession ECS1/BRIP 70272 and B. bassiana accession B27/BRIP 70267 have considerable potential for K. macadamiae control, and should be developed into biological insecticides for integration into macadamia pest management programs.