Pathogenic effect of four isolates of Beauveria bassiana (Bals.) Vuill. (Hyphomycetos) on larvae of Bombyx mori (L.) (Lepidoptera: Bombycidae) under laboratory conditions.

Abstract

The art for rearing insects that produce silk and the utilization of the latter is known as Sericulture. Bombyx mori (L.) is an insect that produces the largest amount of silk. This insect is attacked by protozoa, bacteria, viru­ses, and fungi. Once the coffee berry borer Hypothenemus hampei (Ferrari) was establi­shed in Colombia, some research was con­ducted in order to control this pest by using entomopathogenic fungi. As a result of this strategy, there is some risk related to the effect of spraying the fungi on coffee planta­tions, just near the place where the mulberry crop is established, since the latter, is the only food consumed by the silkworm through­out its life span. The main aim of this ex­periment was to determine the differences in pathogenicity of four isolates of B. bassiana to the silkworm. The isolates Bb-9002, Bb­9022, Bb-9105, and Bb-9107 fromH. hampei, Nephotettiv cincticeps (Ulher), Perileucop­tera coffeella (Guérin - Méneville) and B. mori, respectively, were used. Groups of 50 larvas (five replicates) were inoculated with a concentration of 1 x10⁷ conidia ml, of each isolate, respectively. During the evaluation, the mortality caused by a virus, which produ­ces the «Nuclear Polyhedrosis» (VNP) was registered. Larvae inoculated with the isolate Bb-9107 showed the highest percentage of mortality (10%), followed by the isolate Bb­9105. Both isolates were obtained from lepi­doptera. The highest percentage of viral mor­tality observed was also on larvae infected with the isolate Bb-9107.