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Variability of Pathogenic Activity of Entomogenous Fungi (Hyphomycetes) towards the Legume Flower Thrips, Megaluroihrips sjostedti (Trybom) (Thysanoptera: Thripidae) and their Potentials for Biological Control
Abstract:
Twenty-two strains of entomopathogenic fungi were tested in the laboratory to determine their pathogenicity to adult Megalurothrips sjostedti (Trybom). All the fungal strains were pathogenic to the insect. Beauveria bassiana and Metarhizium anisopliae strains caused mortality ranging between 29 to 100% and 54 to 100%, respectively. In contrast, VerticiIlium lecanii and Paecilomycesfumosoroseus were less virulent, causing mortality ranging between 29 to 68% and 13%, respectively. The LT50 of the most virulent B. bassiana andM. anisopliae strains was 2.7 and 2.4 days, respectively. The LC50 for the most active B. bassiana strain was 7.9 x 106 conidia ml”1. The LC50 for the most active strain of M anisopliae was 1.3 x 106 conidia ml”1. Two strains of B. bassiana and four strains of M anisopliae were found to be highly pathogenic to M. sjostedti which suggests a potential for their use in biological control of the pest The effect of temperature on germination, radial growth and pathogenic activity of two strains of B. bassiana and four strains of M. anisopliae selected during the screening against M sjostedti, was studied in the laboratory. Germination, radial growth and pathogenic activity were low for all strains at 15°C. Optimum temperature for germination, radial growth and pathogenic activity ranged between 25-30°C. The fastest growing strain at 25-30°C wasM anisopliae IC1PE 69. Compared to other strains, ICIPE 69 also appeared to have a broad temperature range of pathogenic activity against the pest The effect of M anisopliae strain ICIPE 69 was tested against M sjostedti developmental stages. All stages of M sjostedti were susceptible to infection by A/, anisopliae. However, larval and pupal stages were less susceptible to fungal infection than the adult stage. Mortality in all stages was dose-dependent with the highest mortality occurring at 1 x 108 conidia ml”1. Daily number of pollen emptied in infected thrips was reduced within 24 h in adults but more slowly in larval thrips Fecundity, egg fertility and longevity in adult surviving larval infection were significantly reduced compared to the control treatment.
Variability of Pathogenic Activity of Entomogenous Fungi (Hyphomycetes) towards the Legume Flower Thrips, Megaluroihrips sjostedti (Trybom) (Thysanoptera: Thripidae) and their Potentials for Biological Control
