Pathogenicity of native isolates of Isaria fumosorosea (Deuteromycotina: Hyphomycetes) on immature whitefly Bemisia tabaci Gennadius (Hemiptera: Aleyrodidae) and their genetic variability

Abstract

The use of chemical insecticides to manage Bemisia tabaci has caused serious damage to the environment and has also selected resistant populations. The use of biological control agents, such as entomopathogenic fungi is an excellent component of integrated pest management programs. In the present study, the virulence of four native isolates (Pf-Tim, Pf-Tiz, Pf-Hal and Pf-Tic), as well as a commercial strain (Pae-sin) of Isaria fumosorosea was evaluated on eggs and second instar nymphs of B. tabaci. In addition, by the random amplified polymorphic DNA (RAPD) analysis, the genetic variability of the I. fumosorosea isolates was determined. All fungal isolates were more virulent on nymphs than on eggs. The most virulent native isolate for eggs was Pf-Tim, which showed the same effect than that of the commercial strain Pae-sin. As for the effects on nymphs, the native isolate Pf-Tim (5.5 x 104 conidia mL-1) showed the lowest median lethal concentration. This value was not significantly different than that observed for the commercial strain Pae-sin (2.6 x 104 conidia mL-1). As for the RAPD analysis, there was low genetic variability among I. fumosorosea isolates Pf-Tim, Pf-Tic and Pf-Tiz. Key words: Biological control, pest management, entomopathogenic fungi