Chiara Ferracini

Adaptation of Indigenous Larval Parasitoids to Tuta absoluta (Lepidoptera: Gelechiidae) in Italy

ABSTRACT Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) is a serious threat to tomato (Solanum lycopersicum L.) crops in South America. In Europe, after its first detection in Spain in 2006, it rapidly spread through the Mediterranean basin, reaching Italy 2 yr later. The aim of our work was to find indigenous effective biological control agents and to evaluate their potential role in the control of larval populations of T. absoluta in controlled conditions. Nine species of larval parasitoids emerged from field-collected tomato leaves infested by T. absoluta. The most abundant, Necremnus near artynes (Walker) and Necremnus near tidius (Walker) (Hymenoptera:Eulophidae), were tested in laboratory parasitism trials. Furthermore, because the species N. artynes and N. tidius are each reported in literature as an ectoparasitoid of Cosmopterix pulchrimella Chambers (Lepidoptera: Cosmopterigidae) on upright pellitory plants, olfactometer bioassays were performed to assess the response of our parasitoids to the odors of tomato and pellitory leaves infested by T. absoluta and C. pulchrimella, respectively, compared with healthy ones. Both Necremnus species showed good adaptation to the invasive pest, and we observed a high larval mortality of T. absoluta because of host feeding and parasitism. Even olfactory responses highlighted a preference of both wasps for tomato plants infested by the exotic pest. These preliminary results demonstrated a high suitability of these indigenous natural enemies for controlling T. absoluta. Further investigations are needed to confirm their role as potential biological agents in commercial tomato plantations.

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.

Costs and benefits of host feeding in the parasitoid wasp Trichogramma turkestanica

Females of the parasitoid wasp Trichogramma turkestanica Meyer (Hymenoptera: Trichogrammatidae) generally host feed after ovipositing on the first egg of Ephestia kuehniella Zeller (Lepidoptera: Pyralidae) they encounter. We measured the impact of host feeding on the fecundity and longevity of females, in absence of host or food, and on the fitness of their progeny. We also determined if the frequency of host feeding is influenced by the humidity level at which T. turkestanica females developed. Host feeding increased egg production by 70% but decreased female longevity. This impact of host feeding on the longevity of females is probably due to the allocation of carbohydrates to egg production at the expense of somatic maintenance. Humidity did not influence the occurrence or duration of host feeding. The size of individuals developing in eggs on which females host fed was smaller, indicating that their fitness was affected.

Non-target host risk assessment for the parasitoid Torymus sinensis

Torymus sinensis Kamijo (Hymenoptera: Torymidae) has been released throughout Italy for biological control of the chestnut gall wasp. In response to concern about non-target impacts associated with the introduction of this exotic biological control agent, this study aimed at investigating T. sinensis’s host range. In total, 1371 non-target galls were collected in north-central Italy in a two-year period, representing nine different species. Collections were carried out on common oak, downy oak, sessile oak, Turkey oak, and wild rose. A total of five native torymid species were recorded from the non-target galls (Megastigmus dorsalis, Torymus affinis, T. auratus, T. flavipes, and T. geranii), and three ♂♂ T. sinensis individuals emerged from Biorhiza pallida galls collected in the field. Under controlled conditions, most of the non-target galls tested were not suitable hosts for oviposition. T. sinensis females only laid eggs on Andricus curvator. In olfactometer bioassays, higher numbers of T. sinensis females showed more interest to the chestnut galls compared to non-target hosts. This data highlights how T. sinensis has a broader ecological host range than reported in the literature and that it is attracted by non-target hosts other than D. kuriphilus.

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.

Development of a Sequential Plan to Evaluate Neodryinus typhlocybae (Ashmead) (Hymenoptera: Dryinidae) Population Associated with Metcalfa pruinosa (Say) (Homoptera: Flatidae) Infestation in Northwestern Italy

Abstract Metcalfa pruinosa (Say) is an exotic pest introduced into Italy in the early 1980s. It is a polyphagous pest and can infest several plant species used in agriculture, forest, and urban systems. To control this pest, Neodryinus typhlocybae (Ashmead), a specialist parasitoid attacking young M. pruinosa instars, was introduced in Italy starting in 1987. From 1999 to 2001, the establishment of N. typhlocybae was evaluated and a sampling plan developed to estimate its cocoon population density. The spatial aggregation of the cocoons was analyzed by Taylor’s power law. The aggregation index ranged from 1.064 to 1.136 and a common value (b = 1.1) was estimated. Sequential sampling was shown to be the more practical and least time consuming sampling method. The peak of the parasitoid cocoon population at the end of July (26th to 30th week of the year) is a suitable period in northern Italy to monitor the activity of the parasitoid and to estimate the field parasitization. The potential of the sampling method is discussed, with the aim to evaluate the impact of the parasitoid on M. pruinosa populations.

Evaluation of the Community of Native Eulophid Parasitoids on Cameraria ohridella Deschka and Dimic in Urban Areas

Abstract The parasitoid complex associated with the exotic leafminer Cameraria ohridella Deschka and Dimic (Lepidoptera: Gracillariidae), which attacks horse chestnut (Aesculus hippocastanum L.), was studied in the urban environment of Turin (northern Italy). The studies were carried out over 5 yr after the first detection of the pest in our region in 1999. To evaluate parasitism, 438,029 leaf mines were examined over the 5-yr period, of which 29,033 were found to be parasitized (6.6%). Also, ornamental broadleaf trees attacked by other native gracillariid leafminers and located in the proximity of the target horse chestnut trees were sampled. A total of 11 parasitoid species (Hymenoptera: Eulophidae) were recorded on C. ohridella, and the most common species were Minotetrastichus frontalis (Nees), Closterocerus trifasciatus Westwood, and Pnigalio agraules (Walker). The first species accounted for >77.5% of all parasitoids collected. Cirrospilus talitzkii Bouček was found for the first time in 2005. The high population level of the pest and the low parasitism rate show that the parasitoid complex is currently inadequate to contain C. ohridella populations effectively. The most frequent parasitoids of the moth were also found on the most common broadleaf trees in the studied area, showing how native leafminer parasitoid species are able to switch to other hosts. These results show that both native and broadleaf plants species may potentially provide an important reservoir of parasitic wasps to help protect a simple biotope, such as the urban environment, from pests.

Post-release evaluation of non-target effects of Torymus sinensis, the biological control agent of Dryocosmus kuriphilus in Italy

A post-release study was performed to assess the impact of Torymus sinensis (Hymenoptera: Torymidae), the biological control agent of Dryocosmus kuriphilus (Hymenoptera: Cynipidae), on native cynipid gall inducers in Italy. In total, 14,512 non-target galls were collected, corresponding to seven genera: Andricus, Aphelonyx, Biorhiza, Cynips, Diplolepis, Neuroterus, and Synophrus, and 8708 chalcid parasitoids were recorded. The Torymidae family accounted for about 30%, and Bootanomyia (=Megastigmus) dorsalis, Torymus affinis and T. flavipes were the most represented species. A total of 116 T. sinensis emerged from 15 different oak galls, mainly Andricus curvator and A. inflator. In controlled conditions, oviposition was recorded on A. cydoniae, A. grossulariae and A. lucidus, while no mating with native congeneric species occurred. This paper confirms the realised host-range expansion by T. sinensis. Even if it were extremely difficult to evaluate its magnitude, the impact appears minimal, and an occasional feeding with no changes in the distribution or abundance of non-target hosts is expected.

Aesculus pavia foliar saponins: defensive role against the leafminer Cameraria ohridella.

BACKGROUND Recently, the leafminer Cameraria ohridella Deschka & Dimic has caused heavy damage to the white-flowering horse chestnut in Europe. Among the Aesculus genus, A. pavia L. HBT genotype, characterised by red flowers, showed an atypical resistance towards this pest. Its leaves, shaken in water, originated a dense foam, indicating the presence of saponins, unlike the common horse chestnut tree. The aim was to isolate and identify these leaf saponins and test their possible defensive role against C. ohridella. RESULTS Spectroscopic analyses showed that A. pavia HBT genotype leaves contained a mixture of saponins, four of which were based on the same structure as commercial escin saponins, the typical saponin mixture produced by A. hippocastanum and accumulated only within bark and fruit tissues. The mixture showed a repellent effect on C. ohridella moth. The number of mines detected on the leaves of A. hippocastanum plants treated with A. pavia HBT saponins through watering and stem brushing was significantly lower than the control, and in many cases no mines were ever observed. CONCLUSION The results showed that the exogenous saponins were translocated from roots/stem to the leaf tissues, and their accumulation seemed to ensure an appreciable degree of protection against the leafminer.

Insect vectors of plant pathogenic Mollicutes in the Euro-Mediterranean region

This paper embeds a review of insect vectors of Mollicutes plant pathogens in Europe and Middle East. A dissertation on systematic and phylogeny introduces the two groups of vectors: Auchenorrhyncha and Sternorrhyncha (Psyllidae). Aspects involving the differences in the transmission process of pathogens and the relationships of insect vectors and host plants have been considered. From an environmental point of view, flight activity, dispersal and spatial distribution have been dealt with in relationship with plant disease epidemiology. Finally, the main control and monitoring strategies have been discussed, along with the problem concerning alien species and quarantine regulations.