Morphological characterization of the antenna of Torymus sinensis (Hymenoptera: Torymidae) and a comparison within the superfamily Chalcidoidea.

The parasitoid Torymus sinensis (Hymenoptera: Torymidae) has been successfully used in Italy since 2005 for biological control of the invasive cynipid Dryocosmus kuriphilus (Hymenoptera: Cynipidae), highly destructive for the economically relevant Castanea sativa (Fagales: Fagaceae). In order to investigate the morphological aspects related to sensorial behavior, a fine morphology study of the antennae and their sensilla was conducted by scanning electron microscopy on both sexes of T. sinensis. The antennae, composed of a scape, a pedicel and a flagellum with ten flagellomeres, had chaetic sensilla of six subtypes, placoid sensilla of three subtypes, trichoid sensilla, sensilla with a roundish grooved tip, and coeloconic sensilla. The chaetic sensilla of the first three subtypes were found in the scape and in the pedicel, and those of the last three subtypes, together with trichoid, roundish grooved tip and coeloconic sensilla, were found only on flagellomeres. Sexual dimorphism was detected in the morphology of the proper pedicel and the flagellum, and in the presence and distribution of the sensilla and their subtypes. The morphological aspects of the antenna of T. sinensis and of its sensilla were compared with those found in the family Torymidae and in other families of the extremely diverse superfamily Chalcidoidea.

Adaptation of indigenous larval parasitoids to Tuta absoluta (Lepidoptera: Gelechiidae) in Italy.

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.

Assessment of Chestnut Gall Toughness: Implications for a Biocontrol Agent.

(1) Torymus sinensis, the biocontrol agent of the Asian chestnut gall wasp Dryocosmus kuriphilus, is univoltine, but in NW Italy a small percentage of individuals exhibits a prolonged diapause, mainly as late instar larva. (2) In 2020, the diapause was investigated to evaluate its trend over the years. Due to the low survival rate of diapausing T. sinensis adults, the seasonal variation in the galls' toughness was evaluated, thus assuming that dry galls over time can negatively affect emergence. The window of vulnerability of the gall wasp galls was also evaluated in controlled conditions. (3) The results showed that the average number of second year T. sinensis emerging per 100 cells was 0.41 ± 0.05, and dead adults accounted for 4.1 ± 0.23 per 100 cells. Gall toughness resulted in lower values for galls collected in May and June, and then gradually increased over time. In general, no difference was detected in the wall toughness of galls formed during the previous year when compared to current-year dry galls. Oviposition was recorded on all the tested galls collected in May and June, and no difference in the number of oviposition events was detected. Conversely, no oviposition was observed in July. Comparing the number of oviposition events by T. sinensis and the gall toughness, a negative correlation was found (R2 = -0.99). (4) The present findings contribute descriptive information on this gall's structural traits, and the influence on gall wasp management is also discussed.

A Qualitative Analysis of Beekeepers' Perceptions and Farm Management Adaptations to the Impact of Climate Change on Honey Bees.

(1) Background: Bees are the primary animal pollinators in most ecosystems, and honey bees (Apis mellifera L.) are important providers of pollination ecosystem services and products. Climate change is one of the major threats for honey bees. (2) Objectives and methods: Qualitative research using focus group discussions was carried out in northwestern Italy, to investigate the beekeepers' perceptions of climate change effects, the relevant management adaptations, and the main issues affecting the sector. (3) Results: Beekeepers reported several consequences related to severe weather events (weakening or loss of colonies; scarcity of nectar, pollen, and honeydew; decrease or lack of honey and other bee products; greater infestation by varroa; decline in pollination), making it necessary to provide supplemental sugar feeding, intensive transhumance, more effective and sustainable techniques for varroa control, and increased production of nuclei. A strengths, weaknesses, opportunities, and threats (SWOT) analysis was completed, displaying the factors able to strengthen or weaken the resilience of the beekeeping sector to climate change. (4) Conclusions: Thanks to their strong motivation and collaborative attitude, beekeepers succeed in adopting farm and bee hive adaptation strategies that are able to limit the climatic adverse effects. However, these findings highlight how the institutional and financial support for the beekeeping sector should be strengthened and better targeted.

Pheromone-Mediated Mating Disruption as Management Option for Cydia spp. in Chestnut Orchard.

(1) Background: Pheromone-based devices are successfully used to control insect pests in agriculture. (2) Methods: Investigations were conducted to evaluate the effectiveness of mating disruption (MD) to control the chestnut tortrix moths, Cydia fagiglandana and Cydia splendana. Surveys were performed in northern Italy in 2019-2020. MD was carried out using the pheromone dispenser Ecodian® CT. The effectiveness of MD was assessed by recording male adult catches in pheromone-baited sticky traps and larvae in chestnut fruits, comparing MD and control plots. (3) Results: The total number of trapped males was significantly lower in MD plots than in control ones, for all sites and years. Trap catch suppression in MD plots averaged 89.5% and 93.8% for C. fagiglandana and 57.4% and 81% for C. splendana in 2019 and 2020, respectively. The larval infestation rate in fruits did not vary between plots except for one site where a reduction of about 71% in the MD plot was recorded in 2019. (4) Conclusions: Low catches in MD plots turned out to be a good measure of the effectiveness of communication disruption, but no satisfactory data have been obtained regarding fruit infestation, highlighting how the reduction of male catches cannot always be considered as a reliable indicator of successful control. Specific investigations about background population density, dispersal and mating/oviposition behavior are thus essential for a viable management strategy.

An integrated transcriptomic and proteomic approach to identify the main Torymus sinensis venom components.

During oviposition, ectoparasitoid wasps not only inject their eggs but also a complex mixture of proteins and peptides (venom) in order to regulate the host physiology to benefit their progeny. Although several endoparasitoid venom proteins have been identified, little is known about the components of ectoparasitoid venom. To characterize the protein composition of Torymus sinensis Kamijo (Hymenoptera: Torymidae) venom, we used an integrated transcriptomic and proteomic approach and identified 143 venom proteins. Moreover, focusing on venom gland transcriptome, we selected additional 52 transcripts encoding putative venom proteins. As in other parasitoid venoms, hydrolases, including proteases, phosphatases, esterases, and nucleases, constitute the most abundant families in T. sinensis venom, followed by protease inhibitors. These proteins are potentially involved in the complex parasitic syndrome, with different effects on the immune system, physiological processes and development of the host, and contribute to provide nutrients to the parasitoid progeny. Although additional in vivo studies are needed, initial findings offer important information about venom factors and their putative host effects, which are essential to ensure the success of parasitism.

Performance of Pheromone-Baited Traps to Monitor the Seasonal Abundance of Tortrix Moths in Chestnut Groves.

(1) Background: Pammene fasciana (L.), Cydia fagiglandana (Zeller), and C. splendana (Hübner) (Lepidoptera: Tortricidae) are considered key moth pests of chestnut in Europe. (2) Methods: Investigations were performed in 2018-2019 in northern Italy. Sticky traps and commercially available pheromones were used for monitoring; moreover, two experimental pheromone blends were tested. All specimens were identified according to male genitalia and molecular analyses. Newly formed chestnut husks and fruits were randomly collected to evaluate the presence of larvae and/or feeding damage, by comparing it to trap catches. (3) Results: P. fasciana was present in all the sites, whereas Cydia species were recorded in three sites of six, with differences in abundance related to pheromone blends studied. Several non-target species, such as Oegoconia novimundi (Busck) and Cydia ilipulana (Walsingham), were present. Data about the seasonal flight activity are provided. (4) Conclusions: This research contributes to ascertaining the presence and abundance of tortrix moths in Italian chestnut groves, and the presence of non-target species highlights the risk of overestimating catches. Fruit damage recorded did not always reflect catches made by pheromone traps, suggesting that monitoring may underestimate the real size of moths' populations. All of the data acquired are important for planning specific control measures.

Evaluation of the community of native eulophid parasitoids on Cameraria ohridella Deschka and Dimic in urban areas.

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 Boucek 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.

Sequential sampling plan for Cameraria ohridella (Lepidoptera: Gracillariidae) on horse chestnut tree.

A fixed precision sequential sampling plan for estimating the density of the horse chestnut, Aesculus hippocastanum L., leafminer Cameraria ohridella Deschka & Dimic (Lepidoptera: Gracillariidae) was developed. Data were collected from 2002 to 2004 in Turin, northwestern Italy, with the aim of developing a sampling strategy for estimating populations of C. ohridella mines. Taylor's power law was used as a regression model. Sampling parameters were estimated from 216 data sets, and an additional 110 independent data sets were used to validate the fixed precision sequential sampling plan with resampling software. Covariance analysis indicated that there were not significant differences in the coefficient of Taylor's power law between heights of the foliage, months, and years. Dispersion patterns of C. ohridella were determined to be aggregated. The parameters of the Taylor's power law were used to calculate minimum sample sizes and sampling stop lines for different precision levels. Considering a mean density value of five mines per leaf, an average sample number of only 49 leaves was necessary to achieve a desired precision level of 0.25. As the precision level was increased to 0.10, the average sample size increased to 303 leaves. The sequential sampling plan should provide an effective management of C. ohridella in the urban areas, minimizing sampling time and cost, and at the same should be an effective tool to reduce insecticide applications and prevent the esthetic damage.

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.