Annals of Applied Biology (2008) 153, 41-48

S. Ondiaka, N.K. Maniania, G.H.N. Nyamasyo and J.H. Nderitu (2008)
Virulence of the entomopathogenic fungi Beauveria bassiana and Metarhizium anisopliae to sweet potato weevil Cylas puncticollis and effects on fecundity and egg viability
Annals of Applied Biology 153 (1), 41-48
Abstract: The virulence of eight isolates of Metarhizium anisopliae and four isolates of Beauveria bassiana (Ascomycota: Hypocreales) to adult Cylas puncticollis (Coleoptera: Curculionidae) was tested in the laboratory. Insects were sprayed with a standard concentration of 1.0 × 10⁷ conidia mL⁻¹ using Burgerjon's spray tower. All the isolates tested were pathogenic to C. puncticollis. Mortality varied between 77.5% and 84.2% with isolates of B. bassiana and between 62.5% and 89.2% with isolates of M. anisopliae, 26 days post-treatment. The lethal time to 50% mortality for the 12 isolates varied between 9.7 and 18.5 days. Four isolates, M. anisopliae International Centre of Insect Physiology and Ecology (ICIPE) 18 and ICIPE 62 and B. bassiana ICIPE 275 and ICIPE 114 were selected for dose-response mortality [lethal concentration to 50% mortality (LC₅₀)] bioassays. Five concentrations (1.0 × 10⁶, 3.0 × 10⁶, 1.0 × 10⁷, 3.0 × 10⁷ and 1.0 × 10⁸ conidia mL⁻¹) of both fungal species were used. B. bassiana ICIPE 275 was the most active isolate with LC₅₀ value of 0.7 × 10⁶ conidia mL⁻¹. The effect of fungal infection on feeding, fecundity and egg viability of C. puncticollis adult females was also investigated under laboratory conditions. M. anisopliae isolate ICIPE 18 and B. bassiana isolate ICIPE 114 were tested for feeding experiment using six concentrations (0, 1.0 × 10⁶, 3.0 × 10⁶, 1.0 × 10⁷, 3.0 × 10⁷ and 1.0 × 10⁸ conidia mL⁻¹). For reproduction potential (fecundity and egg viability) bioassays, five concentrations (0, 1.0 × 10⁶, 3.0 × 10⁶, 1.0 × 10⁷ and 3.0 × 10⁷ conidia mL⁻¹) of M. anisopliae isolate ICIPE 18 were used. Adult sweet potato weevils (SPWs) treated with M. anisopliae at the concentrations of 3.0 × 10⁷ and 1.0 × 10⁸ conidia mL⁻¹ consumed significantly less food than weevils in the control and B. bassiana treatments at all the concentrations, except at the higher concentration of 1.0 × 10⁸ conidia mL⁻¹, 14 days post-treatment. Female weevils in the control treatments laid more eggs than fungus-treated females. Percentage egg viability differences between controls and fungus treatments were significant at all the concentrations tested, 10 days post-treatment. These results show that B. bassiana and M. anisopliae are pathogenic to SPWs and infection can reduce feeding, fecundity and egg viability.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)
Link to article at publishers website
Database assignments for author(s): Nguya K. Maniania, John H. Nderitu

Research topic(s) for pests/diseases/weeds:
biocontrol - natural enemies
Research topic(s) for beneficials or antagonists:
evaluation - screening - selection
general biology - morphology - evolution

---

Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Cylas puncticollis
Beauveria bassiana (entomopathogen)	Cylas puncticollis
Metarhizium anisopliae (entomopathogen)	Cylas puncticollis