Influence of plant resistance at the third trophic level: interactions between parasitoids and entomopathogenic fungi of cereal aphids

Abstract

Host-plant resistance can affect herbivorous insects and their natural enemies such as parasitoids and entomopathogenic fungi. This tritrophic effect acts on interspecific interactions between the two groups of natural enemies distantly related in phylogenetic terms. The intra- and extra-host aspects of the interaction between the cereal aphid parasitoid Aphidius rhopalosiphi and the entomopathogenic fungus Erynia neoaphidis developing on the grain aphid, Sitobion avenae, on resistant and susceptible wheat (Triticum aestivum) cultivars, were studied. The competitive outcome of the intra-host interaction depended on the timing of parasitoid oviposition and fungal infection and was affected by wheat resistance. In particular, survival of the parasitoid was lower on the resistant wheat cultivar than the susceptible wheat cultivar, when the competitive outcome of the interaction was favourable for either parasitoid or fungal development. Before and after this period the influence of plant resistance was not significant. Furthermore, the extra-host interaction was not affected by the wheat cultivar, although an increase in fungal infection of S. avenae was observed when parasitoids foraged in the experimental arena with sporulating aphid cadavers compared with foraging in the absence of sporulating cadavers. Our results showed that the host plant may affect interspecific interactions between parasitoids and fungi and that these interactions depended on the timing of parasitoid oviposition and fungal infection.

Susceptibilidad del parasitoide Phymastichus coffea LaSalle (Hymenoptera: Eulophidae) a Beauveria bassiana en condiciones de laboratorio

“…De cualquier manera, es conveniente realizar experimentos para validar estos resultados en el campo. Las evaluaciones en laboratorio no siempre refl ejan los niveles de infección que ocurren en condiciones naturales (Goettel et al 1990), debido a que la actividad de los enemigos naturales es afectada por la complejidad del medio (James et al 1995, Fuentes-Contreras et al 1998. Sin duda, los hallazgos reportados en el presente estudio serán importantes para futuros trabajos relacionados con la broca del café en América Latina.…”

Complex interactions between a plant pathogen and insect parasitoid via the shared vector-host: consequences for host plant infection

“…Brodeur and Rosenheim 2000;Harvey 2005;Schofield et al 2005). Often these interactions are highly asymmetric and strongly influenced by temporal priority (Fuentes-Contreras et al 1998;Begon et al 2002). In laboratory systems examining the dynamics of parasitoids and pathogens sharing a lepidopteran host, the sequence of arrival determined which species were ultimately retained in the system and the form of equilibrium that was achieved (Sait et al 2000).…”

Semiochemical-Mediated Oviposition Avoidance by Female House Flies, Musca domestica, on Animal Feces Colonized with Harmful Fungi

“…For example, microorganisms have been shown to curtail the number of burying beetle, Nicrophorus quadripunctatus, offspring that complete development (Wilson et al 1984). Competition with fungal (Fuentes-Contreras et al 1998;Askary and Brodeur 1999), viral (Hochberg 1991), or bacterial (Chilcutt and Tabashnik 1997) pathogens of host insects adversely affects even parasitoid larvae, which exploit living organisms. The outcome of this competition is dependent upon the relative timing of infection.…”