Screening of Fungal Pathogens Against Silverleaf Whitefly

Abstract

Twenty-one strains of the entomopathogenic fungi Beauveria bassisna (Bolsamo) Vuillemin, Paecilomycesfarinosus (Holm ex Ef Gray) Brown and Smith, Metarhizium anisopliae (Metschnikoff) Sorokin, and Verticillium lecanii (Zimmermann) Viegas were evaluated for pathogenicity and virulence to silverleaf whitefly (SLWF), Bemisia argentifolli (Bellows & Perring) first instar larvae using a leaf-dip bioassay method. Conidia dilutions from each strain at 0 (control, 0.05% TweenR), 1.0X104, 1.0X105, 1.0X106, and 1.0X107spores/ml were prepared in 0.05% Tween and leaves were treated by immersion in these suspensions. Assessment of first instar larvae
infections were made 7 and 14 d post treatment. All results indicated that all strains infected first instar larvae. Mortality for all strains was £ 76% at d 7, but after 14d three strains exceeded 90% mortality. The mean percent mortality induced by strains MLC3 and L3009 of B. bassiana and strain L3444 of P. farinosus was 92.6, 92.3, and 90.5, respectively. These were selected for bioassay of eggs, adults, first and third instars SLWF together with V. lecanii (FR20), a whitefly-active strain identified in a prior screening programme.