Comparative Susceptibility of Otiorhynchus sulcatus and Sitona lineatus (Coleoptera: Curculionidae) Early Stages to Five Entomopathogenic Hyphomycetes

Abstract

Conidial suspensions of Beauveria bassiana (Balsamo) Vuillemin, Metarhizium anisopliae var. anisopliae (Metschnikoff) Sorokin, Metarhizium flavoviride Gams and Rozsypal, Paecilomyces farinosus (Dickson ex Fries) Brown and Smith, and Paecilomyces fumosoroseus (Wize) Brown and Smith were tested in the laboratory for pathogenicity to Otiorhynchus sulcatus F. and Sitona lineatus L. eggs and neonate larvae. All fungi tested, except B. bassiana , were infectious for O. sulcatus eggs. Metarhizium flavoviride outperformed all other fungi and it was the only species effective against Sitona lineatus . The grubs of O. sulcatus and S. lineatus hatching from treated but apparently unaffected eggs were susceptible to all fungi tested and the overall cumulative mortality for eggs and grubs was high in both insect species. Metarhizium flavoviride with a very low LD50 (1 × 101 spores ml−1) was also the fastest to attack O. sulcatus (LT50 = 9.6 days at 108 conidia ml−1). The lowest LD50 for S. lineatus was 4.2 × 102 conidia ml−1 with P. fumosoroseus and M. flavoviride was the fastest acting fungus with a LT50 = 6.9 days at 108 conidia ml−1. INRA isolates M. flavoviride 88 and B. bassiana 142 are promising candidates to control both weevil species.