Bioassay of Potential Entomopathogenic Fungi for the Control of Silverleaf Whitefly

Abstract

Strains of Beauveria bassiana (Balsamo) VuiUemin, Paecilomyces farinosus (Holm ex Ef Gray) Brown and Smith and VerticilUicm lecanii (Zimmermann) Viegas were evaluated for their pathogenicity to adults, eggs, first and third instars of silverleaf whitefly (SLWF), Bemisia &rgerttifoUi (Bellows & Perrrng). Comdia dilutions were prepared in 0.05% Tween® and leaves treated by immersion in these suspensions. Assessment of nymphal infections were made 2, 3, 5, 7, and 10 days post treatment. Infection rates assessment in adults and eggs were made 14 d post-treatment. All strains were pathogenic to nymphs and adults. None of the strains was pathogenic to eggs. Strains L3444 (P. farinosus ) and L3009 ( B. bassiana) were the most pathogenic to first instars ancl adults with LCX and LCX values o f'7.3X104 and 3.1X106 spores/ml, and 1.3X10s and 1.0X107 spores/ml, respectively. Strain FR20 (V. lecanii) was the most pathogenic strain for third instars with LC*, and LC* values of 4.8X103 and 7.4X105 spores/ml, respectively. Results imply that L3444 and L3009 are the most efficient strains based on their pathogenicity to first instars and adults. Results under laboratory conditions are discussed in relation to their potential for management of silverleaf whitefly in greenhouses.