Fecundity and egg fertility in the adult Colorado beetle (Leptinotarsa decemlineata) surviving larval infection by the fungus Beauveria bassiana
1991
Fargues, J. | Delmas, J.-C. | Augé, J. | Lebrun, R.A.
Secondary effects of the entomopathogenic hyphomycete Beauveria bassiana (Bals.) Vuill. were investigated on adults of Leptinotarsa decemlineata Say (Coleoptera: Chrysomelidae) treated as newly moulted 4th-instar larvae. Fecundity and egg hatching were monitored in surviving females mated with surviving males. When reared at 22 °C, adult survivors showed a lessening of their reproductive potential during their whole life. According to the fungal inoculum dosage, the reductions of the total number of eggs laid per female and the mean number of eggs per egg mass ranged from 20% to 56% and from 18% to 46%, respectively. In contrast, at 25 °C, the fecundity of survivors was not affected by the fungal infection. This variability of the secondary effects of B. bassiana according to temperature conditions might be related to the lower infection level of treated larvae at 25 °C. Moreover, at both temperatures, eggs laid by females surviving fungal infection as larvae were as fertile as eggs laid by control insects. It is concluded that secondary effects of B. bassiana on the fecundity of the Colorado Potato Beetle are temperature-dependent and that they could become negligible at high temperatures under field conditions.
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