Fecundity and egg fertility in the adult Colorado beetle (Leptinotarsa decemlineata) surviving larval infection by the fungus Beauveria bassiana

Abstract

Secondary effects of the entomopathogenic hyphomycete Beauveria bassiana (Bals.) Vuill. were investigated on adults of Lept#zotarsa 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 ~ 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~o and from 18 ~ 4 to 46 ~o, 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.

Virulence and Pre-Lethal Reproductive Effects of Metarhizium anisopliae var. anisopliae on Pseudococcus viburni (Hemiptera: Pseudococcidae)

“…In this study effects of decreasing egg fertility on survival females at doses of 10 5 and 10 6 conidia mL -1 were not detected. Similar results on egg fertility were observed on B. tabaci (Hemiptera: Aleyrodidae) and Leptinotarsa decemlineata (Coleoptera: Chrysomelidae) using B. bassiana (Fargues et al, 1991). Likewise, inoculating directly on eggs of Bemisia argentifolii with Verticillium lecanii Zimmermann, this showed no pathogenic effects, however all other developmental stages of the species were affected by the pathogen (Gindin et al, 2000).…”

“…Also temperature can influence fecundity response. Leptinotarsa decemlineata treated with B. bassiana decreased its reproductive output at 23 ºC, but not at 25 ºC (Fargues et al, 1991). In our research this effect was not evaluated, since a constant 23 ± 1 °C was used.…”

Influence of Lecanicillium attenuatum on the development and reproduction of the cotton aphid, Aphis gossypii

“…Insect reproduction and longevity are affected by various factors such as temperature (Kocourek et al, 1994;Kersting et al, 1999), nutritional quality (Nevo and Coll, 2001), pesticides (Rongai and Cerato, 1996), and entomopathogens (Sait et al, 1994;Fargues et al, 1991). Although reproduction, longevity and development time are key factors in aphid population dynamics, information is lacking on the influence of entomopathogenic fungi on nymphal development time, insect fecundity and life span (Fargues et al, 1991;Mulock and Chandler, 2001;Zaki, 1998). It is important to understand the influence of the pathogen on the developmental period and reproduction of an insect pest to develop a successful biological control program.…”

Effects of combining Beauveria bassiana and Nosema pyrausta on the mortality of Ostrinia nubilalis

“…Similar reductions in numbers of laid eggs were also demonstrated in other host-entomopathogen systems, e.g. Chilo suppressalis (Walker, 1863) -B. bassiana [42], Leptinotarsa decemlineata (Say, 1824) -B. bassiana [43] and Diabrotica virgifera virgifera (LeConte, 1868) -B. bassiana [44]. Entomopathogenic fungi affect the host insect through a combination of events including mechanical damage by hyphal growth, nutrient depletion, and production of toxins.…”