Ambra Quacchia

Parasitoid recruitment to the globally invasive chestnut gall wasp Dryocosmus kuriphilus

The chestnut gall wasp Dryocosmus kuriphilus is a global pest of chestnut (Castanea). Established as a pest in the mid 20th century in Japan, Korea and the USA, this species has now reached Europe. Successful deployment of a biocontrol agent, Torymus sinensis, in Japan has led to its early release in Italy. Here we provide the first overview of the natural enemies associated with D. kuriphilus in its native and invaded ranges, and discuss general patterns in community development. We then use what is known about European oak gall wasp communities to predict possible future developments for D. kuriphilus, and possible interactions between parasitoid communities attacking hosts on chestnut and oaks.

Chalcid parasitoid community associated with the invading pest Dryocosmus kuriphilus in north-western Italy

Abstract.  1. Biological invasions of exotic species pose a major threat to native biodiversity. Invaders are known to have direct impacts on native species; however, less well studied are the indirect impacts mediated through the integration of invaders into trophically linked communities.

Torymus sinensis: a viable management option for the biological control of Dryocosmus kuriphilus in Europe?

The chestnut gall wasp Dryocosmus kuriphilus is a global pest of chestnut (Castanea spp). Established as a pest in the mid-twentieth century in Japan, Korea and North America, this species was first reported in Europe in 2002. Following the successful release of a biological control agent Torymus sinensis in Japan, this parasitoid species has been released in Italy since 2005. Here we discuss the potential of T. sinensis as a viable management option for the biological control of D. kuriphilus in central Europe. We suggest that more consideration should be given to determining, (i) the conditions under which T. sinensis may attack alternative native gall wasp hosts and (ii) the likelihood of hybridization of this species with native Torymus. Both issues are central to predicting unassisted range expansion by released T. sinensis, and to assess the environmental risks associated with a more widespread release of this species in Europe.

Can the Geranium Bronze, Cacyreus marshalli, become a threat for European biodiversity?

Cacyreus marshalli Butler is an invasive species in many parts of Europe and Mediterranean area. In Europe, its larvae normally feed on pelargoniums. We investigated its potential to spread to native Geranium spp. and evaluated the conservation risks that such a shift would pose for both native geraniums and cohabitant butterflies. The host plant preferences of the Geranium Bronze were investigated under controlled conditions. Studies included both no-choice and multi-choice tests, respectively using 9 and 6 Italian native Geranium spp. Host plant preferences were evaluated by counting the number of eggs laid on individual plants and following butterfly development until adult emergence. Under no-choice conditions, at least one egg was recorded on each tested plant, except for G. phaeum L. All the plants on which oviposition occurred were fully suitable for larval development. The butterfly, however, clearly preferred three species, i.e. G. pratense L., G. sanguineum L. and G. sylvaticum L. for oviposition. In multi-choice trials, females laid at least one egg on all the tested plants, with a preference for G. pratense and G. sylvaticum. In presence of Pelargonium spp. plants, however, no oviposition was observed on any Geranium spp. We assessed offspring fitness measuring their wingspan. No statistical differences were detected in the wingspan between adults emerged from Geranium and Pelargonium. Cacyreus marshalli represents a potential threat for both native geraniums and for Geranium-consuming lycaenids, such as Aricia nicias Meigen and Eumedonia eumedon Esper.

Acceptance and suitability of Cacyreus marshalli (Lepidoptera: Lycaenidae) as host for three indigenous parasitoids

Laboratory tests were conducted in Italy to evaluate the acceptance and suitability of the alien butterfly Cacyreus marshalli Butler as host for three indigenous parasitoids, Trichogramma brassicae (Bezdenko), Exorista larvarum (L.) and Brachymeria tibialis (Walker). Only E. larvarum and B. tibialis showed potential to adapt to C. marshalli. Their contribution to biological control appeared to be especially related to host mortality due to incomplete parasitoid development.