Control of the Banded Fruit Weevil, Phlyctinus callosus (Schönherr) (Coleoptera: Curculionidae), Using Entomopathogenic Fungi

Abstract

Phlyctinus callosus (Schönherr) (Coleoptera: Curculionidae), the banded fruit weevil (BFW), is a sporadic pest, causing damage to fruits, leaves and roots of deciduous fruits and grapevines in the Western Cape Province. Using trunk barriers to prevent the flightless weevils from reaching the leaves and fruits is labour-intensive. Entomopathogenic fungi (EPF) are effective biocontrol agents for the control of soil-borne and above-ground insect pests. Different EPF isolates were screened at 1 × 106 conidia/ml for virulence against different life stages (larvae, pupae and adults) of the BFW. The results indicated that unformulated, laboratory-cultured Beauveria bassiana 1 (Broadband®) and Metarhizium anisopliae 1 (Meta 69®) resulted in significantly higher BFW larval mortality of 97 % and 93 %, respectively, than B. bassiana 2 (Eco-Bb®) with 58 % mortality. Beauveria bassiana 1 (92 %) resulted in significantly higher pupal mortality than B. bassiana 2 (68 %) and M. anisopliae 1 (66 %). Beauveria bassiana 1 caused 90 % adult BFW mortality, which differed significantly from that obtained with B. bassiana 2 (69 %) and M. anisopliae 1 (65 %). A local EPF isolate (EA2) was compared with the commercial EPF isolates, and B. bassiana 1 (92 %) again caused significantly higher mortality of BFW adults compared to B. bassiana 2 (65 %), M. anisopliae 1 (60 %) and M. anisopliae isolate EA2 (64 %). In a sand bioassay using final instar BFW larvae, B. bassiana 1 (85 %) resulted in higher mortality than both B. bassiana 2 (55 %) and M. anisopliae 1 (70 %). The results indicated that all the commercial EPF isolates were effective against the immature and adult stages of the BFW, but with clear differences between isolates. Beauveria bassiana 1 consistently caused the highest BFW mortality under laboratory conditions. Large-scale field trials with the formulated commercial products are recommended to further demonstrate the potential use of this biocontrol agent in integrated pest management programmes.