Dryocosmus Kuriphilus Research Articles

Mapping and transcriptomic approches implemented for understanding disease resistance to Phytophthora cinammomi in Castanea sp

The European chestnut, Castanea sativa Mill, covers a total area of 2.53 million hectares two million of which are chestnut forests, i.e. forests where chestnut is the dominant tree species, being the remaining 0.53 million hectares devoted to fruit production (20.9% of the total chestnut-growing area). Chestnut fruit production in Europe declined considerably during the XX century to the current 200,000 t (almost 300 million euros). This decline arose mainly due to serious diseases and changes in the structure of society. Towards the end of the century, there was a sharp increase in chestnut demand which triggered new planting and the restoration of old orchards throughout Europe, although ink disease (Phytophthora spp.), canker blight (Cryphonectria parasitica (Murrill) M.E. Barr.) and more recently Dryocosmus kuriphilus Yasumatsu, still represent major threats to the species. In Europe, chestnut breeding has been focused on the improvement of cultivars and rootstocks through selection and hybridisation with Asian species resistant to ink disease. Considerable success was obtained using this approach, however little information was acquired until now on the genetic basis of resistance in chestnut. A set of interspecific crosses were established between European chestnut and Asian species and two separate full-sib pedigrees have been produced, SC (C. sativa x C. crenata) and SM (C.sativa x C. mollissima). The goal is to perform DNA marker:trait association analysis to identify QTLs related to ink disease metrics and also to identify putative resistance genes to P cinnamomi using a transcriptomic approach. An overview of the study will be presented including the genotyping of the mapping population (parents and progenies) with nuclear SSR markers designed for Castanea mollissima and provided by the American team of Fagaceae Genomics Project, for the construction of the first genetic linkage map. The methodologies implemented for the determination of the metrics of resistance of mapping population, for further identification of QTLs, will also be presented.

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.

A native and an introduced parasitoid utilize an exotic gall-maker host

Dryocosmus kuriphilus (Hymenoptera: Cynipidae) is non-native to North America and induces formation of galls on petioles and leaves of all chestnut (Castanea spp., Fagales: Fagaceae). We investigated the interactions between the gall wasp D. kuriphilus, a native parasitoid, Ormyrus labotus (Hymenoptera: Ormyridae), and a non-native parasit- oid, Torymus sinensis (Hymenoptera: Torymidae). Galls were collected monthly from May to August and in January from four locations in the United States consisting of orchard-grown hybrid chestnuts (Hiram, OH and Meadowview, VA), suburban-grown orna- mental Chinese chestnuts (C. mollissima) (Broadview Heights, OH), or forest-grown American chestnuts (C. dentata) (Bowling Green, KY). Parasitoids were removed from galls and T. sinensis and O. labotus were identified using PCR-markers. The relative abundance of each parasitoid was compared in relation to collection date, habitat, presence of alternative hosts, and gall characteristics. T. sinensis was col- lected from each location and date, and was dominant in the orchard and suburban locations. However, relatively more O. labotus were collected within the forest, which had significant oak component and alternative cynipid hosts. O. labotus was only col- lected in spring and early summer, indicating the use of different summer and winter hosts. Observations suggest that in addition to parasitizing D. kuriphilus, O. labotus hyperparasitizes T. sinensis. T. sinensis has a longer ovipositor than O. labotus, and parasitized larger galls. This study improves our understanding of interactions between an invasive gall wasp, an intro- duced parasitoid, and native parasitoids, and illustrates novel relationships that may form as exotic species expand their geographic range.

Chestnut gall wasp (Dryocosmus kuriphilus) infestations: new opportunities for the chestnut blight fungus Cryphonectria parasitica?

The invasive chestnut gall wasp Dryocosmus kuriphilus (Cynipidae) is one of the most important insect pests on Castanea species worldwide (EPPO, 2005). In 2009, D. kuriphilus was found for the first time in southern Switzerland, most…

Finding of Torymus koreanus (Hymenoptera: Torymidae) attacking Dryocosmus kuriphilus (Hymenoptera: Cynipidae) in Japan

Torymus koreanus (Hymenoptera: Torymidae) was reared from galls of Dryocosmus kuriphilus (Hymenoptera: Cynipidae) for the first time in Japan. We here report morphological features and partial mtDNA sequencing data of T. koreanus. Torymus koreanus has several common characteristics with species of the cyaneus group defined by Zavada (2003). According to the key to species groups defined by Graham and Gijswijt (1998), it does not belong to any species group because of the entire posterior margin of metasomal tergum five.

Chemical Cues for Host Location by the Chestnut Gall Wasp, Dryocosmus kuriphilus

Dryocosmus kuriphilus is one of the most damaging pests of Castanea spp. Behavioral, chemical, and electrophysiological investigations were employed to examine the role of plant volatiles for host location by this thelytokuos cynipid. Y-tube olfactometer bioassays showed that adult wasps are significantly attracted by C. sativa twigs with at least 1-hr-old mechanical damage. Odors of undamaged host seedlings, intact twigs, and twigs with a fresh mechanical damage were not attractive. Wasps were repelled by plant materials of the non-host Prunus laurocerasus. Fourteen compounds, mainly general green leaf volatiles, were identified in the head-space of attractive host plant twigs by gas chromatography coupled to mass spectrometry. All compounds elicited dose-dependent antennal responses in adult wasps. A synthetic blend comprising all identified compounds in the same ratio as in the attractive host source induced significant positive responses in Y-tube olfactometer bioassays. The study gives a basis for future identification of host plant attractants that could contribute to semiochemical-based monitoring and management practices of this pest.

Interazioni tra cinipide galligeno e cancro della corteccia: una nuova criticità per il castagno

Abstract: The fast spread of Chinese gall wasp (Dryocosmus kuriphilus) represents a new constraint factor for chestnut stands and orchards in Italy. So far, the favourable effect of hypovirulence in Cryphonectria parasitica-Castanea sativa patho-system allowed the development of chestnut cultivation. This situation could be modified by the progressive weakening of the trees caused by intensive attacks of the new parasite. During recent surveys worrying blight damage recurrences were observed in different Italian chestnut areas (in Piemonte, Trentino and Toscana regions) which were highly infested by the Chinese wasp. While biological control treatments against the parasite are carried out, it is necessary to set up integrated protocols for the management of chestnut orchards to allow the survival of trees and their productivity.

Gnomoniopsis associated with necrosis of leaves and chestnut galls induced by Dryocosmus kuriphilus

Chestnut (Castanea spp.) is a very important crop in the Monti Cimini area (Viterbo, Italy) which is seriously infested with the key pest, chestnut gall wasp Dryocosmus kuriphilus (Speranza et al., 2009). In May 2009 such seriously infested chestnut plants in the Monti Cimini area were found with necrotic leaves and galls. Lesions on leaves were irregular and variable in size, lemon green to amber in colour with green margins. Initially, galls were olive green then became dark brown. Inside the galls larvae of chestnut gall wasp were dead. Tissue from the edge of lesions was surface-sterilized using 1% sodium hypochlorite, rinsed in sterile distilled water and aseptically cut in 5–10 pieces not exceeding 5 × 5 mm, plated on potato dextrose agar (PDA) in Petri dishes containing an antibiotic solution (0·2% streptomycin sulphate) and incubated at 20 ± 3°C. Light brown fungal colonies were observed after 1 week close to the tissue and numerous orange slimy masses of conidia were observed on the culture surface. The colonies were regular in outline with a clear and thinner margin. Conidia were oval to oblong, sometimes slightly obovoid, straight or curved and measured 5·5–8·0 μm × 2·0–3·0 μm (mean = 6·8 × 2·5 μm, n = 210). The fungus was identified at Centraalbureau voor Schimmelcultures (CBS, Utrecht, The Netherlands) as an undescribed species from the genus Gnomoniopsis. Identification was based on both DNA sequencing (ribosomal ITS) and morphology (GenBank Accession Nos. EU254851, EU254854, EU254855). The pathogenicity of the fungus was tested in the Tuscia University experimental farm using freshly isolated cultures. Ten chestnut galls were inoculated, after slight pinprick injury, with an aqueous suspension containing 2 × 106 spores/mL and incubated in clean cheesecloth covered with Parafilm. Control-injured galls were sprayed with sterile distilled water and incubated in the same manner. Control plants did not show any disease symptoms 60 days after inoculation. In contrast, the fungus produced characteristic blight symptoms on 90% of the inoculated galls. Similar blight symptoms were observed on chestnut twigs inoculated with 4 mm discs of 7-day-old PDA cultures. Isolations from these lesions confirmed the presence of a fungus identical to Gnomoniopsis. Although chestnut leaf blight has been reported to be caused by some species of the genus Gnomonia (Sogonov et al., 2008), this appears to be the first record of a fungus in the genus Gnomoniopsis associated with the necrosis of chestnut galls caused by Dryocosmus kuriphilus. This Gnomoniopsis sp. has not been reported in Italy on non gall-infested leaves of chestnut trees (Cristinzio, 1986). The relationship between the necrotrophic propensity of Gnomoniopsis and chestnut gall wasp infestation is under investigation. The authors would like to thank the Regione Lazio (Italy) for financial support.

Gene expression following infestation by gall-wasp ( Dryocosmus kuriphilus Yasumatsu) in chestnut ( Castanea spp)

Gene expression following infestation by gall-wasp ( Dryocosmus kuriphilus Yasumatsu) in chestnut ( Castanea spp)

Experience with Dryocosmus kuriphilus Yasumatsu eradication measures in Slovenia*

After causing damage in Asia and the USA, Dryocosmus kuriphilus Yasumatsu recently established in Europe on Castanea. The first outbreak in Europe occurred at a C. sativa nursery for production of plants for planting in Cuneo (Piemonte, Italy) in 2002. The Piemonte official service notified Slovenia that a consignment originating from an infested nursery was sold to Slovenia. Prompt phytosanitary action was taken in Slovenia in 2005 in order to trace back plants from this consignment and prevent establishment of the pest. In the period 2006–2009, intensive surveys of forests and fruit production areas showed absence of the pest in the majority of the Slovenian territory, including the demarcated area from 2005. An earlier introduction of infested plants from Cuneo in January 2004 remained undiscovered until 2007. Despite the radical measure of eliminating the infested orchard and removing infested Castanea trees in the forest bordering this orchard, the pest was not eradicated in this outbreak area. Individual infested trees in the forest were confirmed at a distance of up to 10–34 km in 2008, and a further 15 km in 2009. The results of annual surveys, eradication campaigns based on generic contingency elements and the change of strategy after the finding of infested forests are presented.

DRYOCOSMUS KURIPHILUS YASUMATSU: AN OUTLINE SEVEN YEARS AFTER THE FIRST REPORT IN PIEDMONT (ITALY)

In 2002, for the first time in Europe, the oriental chestnut gall wasp (CGW), D. kuriphilus, was reported spreading in a large chestnut area in the south of Piedmont (Northwest Italy). Movement of infested plants from nurseries of this area has allowed the pest to progressively reach many other regions in Italy. CGW infestation has contributed, together with other factors such as drought and fungal diseases, to a significant reduction in chestnut fruits production. Death of chestnut trees due to CGW attack, however, has so far never been observed. Chemical treatments have proved ineffective for preventing the diffusion of this pest. Indigenous parasitoids, shifting from oak cynipids, show a low rate of parasitization on CGW. Since the first years of the outbreak, the Plant Health Service of Regione Piemonte has been trying to face the emergency, developing different activities: monitoring of chestnut areas, survey of nurseries, funding of research projects for biological control and evaluation of cultivar susceptibility.

Gall Structure Affects Ecological Associations ofDryocosmus kuriphilus(Hymenoptera: Cynipidae)

Gall wasps (Hymenoptera: Cynipidae) induce structures (galls) on their host plants that house developing wasps and provide them with protection from natural enemies. The Asian chestnut gall wasp, Dryocosmus kuriphilus Yasumatsu, is an invasive pest that is destructive to chestnut (Castanea spp.). An improved understanding of the interactions among D. kuriphilus, its host, and its natural enemies is critical for the development of effective management strategies against this pest. The objective of our study was to evaluate the D. kuriphilus community interactions, and relate these interactions to variations among gall traits. Galls were collected from four locations throughout the eastern United States from May (gall initiation) through August (after gall wasp emergence), and January. Gall characteristics (volume, weight, and schlerenchyma layer thickness), gall inhabitants (D. kuriphilus, parasitoids, and chamber fungi), and other community associates (insect herbivores and lesions thought to be caused by endophytes) were evaluated and correlated using canonical correlation analyses. The primary mortality factors for D. kuriphilus were parasitism, gall chamber-invading fungi, and failure of adult gall wasps to emerge. Larger gall size and thicker schlerenchyma layers surrounding the larval chambers were negatively correlated with parasitoids and chamber fungi, indicating these gall traits are important defenses. External fungal lesions and insect herbivory were positively correlated with the absence of D. kuriphilus within galls. This study provides support for the protective role of cynipid galls for the gall inducer, identifies specific gall traits that influence gall wasp mortality, and improves our knowledge of D. kuriphilus ecology in North America.

ECONOMIC ASPECTS OF THE CHESTNUT MARKET IN ITALY

This work presents an overview of the chestnut cultivation sector in Italy, with particular reference to the chief economic and market aspects. The main purpose is to adequately quantify the significance of a species which, although of marginal consequence in Italy's agri-food industry is, however, of vital importance for the areas in which it is cultivated, ensuring that the local communities can remain there. In Italy, which is the fourth most important chestnut producer in the world and the first in Europe, there are about 800,000 ha of chestnut woods of which 150,000 are orchards. The areas dedicated to cultivated chestnuts are progressively decreasing and currently amount to 54,000 ha distributed amongst some 30,000 enterprises. The annual production of chestnuts is approximately 55,000 tons on average and amounts to a basic value of 60-65 million Euros, which can rise to as much as 165 million Euros considering the (whole chain) Unclear Significant additional revenue from ancillary sources also contributes towards this result to the tune of 15-25 million Euros per year and is obtained from woodland by-products, timber, transport but especially from the numerous wine and food festivals that attract crowds of visitors to all parts of the country. Thus the chestnut becomes a true attraction medium and a valid marketing incentive for these areas. The fact that these results have been achieved is mostly due to the great attention paid to quality, as testified by the seven Community trademarks obtained to date. Future worries include the drop in the supply noted in 2007 and 2008 (up to 30-40% according to estimates and due to the adverse weather conditions) and the aggressive new pathogens, such as the chestnut gall wasp.

Risk assessment of the oriental chestnut gall wasp, Dryocosmus kuriphilus for the EU territory and identification and evaluation of risk management options

Risk assessment of the oriental chestnut gall wasp, Dryocosmus kuriphilus for the EU territory and identification and evaluation of risk management options

CHEMICAL CONTROL OF CHESTNUT WEEVILS IN CENTRAL ITALY

In Central Italy Chestnut Gall Wasp Dryocosmus kuriphilus Yasumatsu, Chestnut Weevils and two Chestnut Moths, Cydia fagiglandana (Zeller) and C. spendana (Hubner) are the key insect pests of chestnut orchards. In Latium Region two species of chestnut weevils, Curculio elephas (Gyll.) and C. propinquus (Desbr.), are represented at 5% and 95% respectively. These two carpophagous insects can generate severe yield losses, variable in the years from 20 to 90%. In order to minimize the rate of damaged chestnuts, chemical control trials were carried out comparing two active ingredients: Thiacloprid and Etofenprox. The results show a higher effectiveness of a.i. Thiacloprid with respect to Etofenprox and control treatments.

Hybridization between introduced Torymus sinensis (Hymenoptera: Torymidae) and indigenous T. beneficus (late-spring strain), parasitoids of the Asian chestnut gall wasp Dryocosmus kuriphilus (Hymenoptera: Cynipidae)

Hybridization between introduced biological control agents and native species is a nontarget effect of biological control. However, the genetic impacts related to introduced insects, especially from the viewpoint of post-release evaluation, remain largely unexplored. Torymus sinensis (Hymenoptera: Torymidae) is a parasitoid wasp introduced from China into Japan to control the invasive Asian chestnut gall wasp Dryocosmus kuriphilus (Hymenoptera: Cynipidae). After T. sinensis was first released in 1982, the damage caused by D. kuriphilus fell greatly. Previous studies showed that hybridization between T. sinensis and indigenous Torymus beneficus (the early-spring strain) was rare in the field, but individuals morphologically intermediate between T. sinensis and T. beneficus then appeared in the field. Here, we examined the frequency of hybridization between T. sinensis and the late-spring strain of T. beneficus by using the internal transcribed spacer 1 (ITS1) region of nuclear rDNA. Increasing numbers of F 1 hybrids were detected every year from 1993 to 1996, reaching 22%. It seems that T. sinensis can hybridize more easily with the late-spring strain of T. beneficus. Morphological indices of the F 1 hybrid type ranged between indices of the late-spring strain of T. beneficus and T. sinensis, with considerable overlap. Simultaneous with the occurrence of the F 1 hybrids, the indigenous late-spring strain of T. beneficus was rapidly displaced by T. sinensis.

STUDY APPROACHES ON THE CHESTNUT GALL WASP, DRYOCOSMUS KURIPHILUS YASUMATSU IN CHINA

Approaches of studies on the chestnut gall wasp, Dryocosmus kuriphilus Yasumatsu in China were documented in this paper. The pest distributes over 16 provinces covering all the chestnut productive area in the country with yield damage 15-30% every year. It was observed only 1 generation each year and seems to reproduce by parthenogenesis. Over wintering as young larvae within the host buds, it feeds acting with the budburst in spring, and its cabin forms with the leaf growth and spread. The adult eclosion is at end of male flower blooming. There have been 28 parasitical wasps reported as the nature enemies of the pest up today. Among them, Torymus sineresis Y. is the most predominant one. Pollarding in winter, releasing natural enemy during April to June, using black light trap from June to September, and utilizing resistant cultivars are the main methods of IPM.

ELECTROANTENNOGRAPHIC RESPONSES OF DRYOCOSMUS KURIPHILUS TO CASTANEA SATIVA LEAF VOLATILES

Electroantennographic (EAG) responses from adults of the chestnut gall wasp, Dryocosmus kuriphilus were recorded on stimulation with a given dose of 22 volatile compounds previously identified from Castanea sativa leaves. All compounds elicited measurable EAGs. The largest EAG amplitudes were recorded in response to the oxygenated monoterpenes, α-terpineol and linalool, and the green leaf volatiles (GLVs), (E)-2-hexenal, (Z)-3-hexen-1-ol, (E)-3-hexen-1-ol and (E)-2-hexen-1-ol. EAGs to hydrocarbon monoterpenes and aromatics were generally weak. In preliminary Y-tube olfactometer bioassays the GLVs, hexyl acetate, (E)-2-hexen-1-ol and (E)-3-hexen-1-ol were attractive when individually tested compared to a solvent control suggesting their possible role in the D. kuriphilus host plant selection. Identification of host plant attractants is useful to develop semiochemically based pest control strategies of the chestnut gall wasp.

ENDEMIC PARASITOIDS OF DRYOCOSMUS KURIPHILUS YASUMATSU (HYMENOPTERA: CINIPIDAE) IN CENTRAL ITALY

The presence of chestnut gall wasp was reported for the first time in Northern Italy in 2002 and has subsequently spread rapidly in Central and Southern Italy. Knowing the harmfulness of this wasp for chestnut growing, we considered essential to inquire the cohort of parasitoids of this new insect for the Italian fauna. This research reports on preliminary results obtained in 2007 on the D. kuriphilus parasitoids in Central Italy. In particular, eight parasitoids species have been found: two Euritomidae [Sycophila biguttata (Swederus) Eurytoma brunniventris (Ratzeburg)], one Pteromalidae [Mosopolobus sericeus (Forster)], three Torymidae [Torymus flavipes (Walker), T. erucarum (Schrank), Megastigmus dorsalis (Fabricius)], one Eupelmidae [Eupelmus urozonus (Dalaman)] and one Ormyridae [Ormyrus pomaceus (Geoffroy)]. We report for the first time the presence of the Torymus erucarum as parasitoid of D. kuriphilus.

DIFFERENTIAL GENE EXPRESSION IN CHESTNUT BUDS FOLLOWING INFESTATION BY GALL-WASP (DRYOCOSMUS KURIPHILUS YASUMATSU, HYMENOPTERA: CYNIPIDAE)

The chestnut gall-wasp Dryocosmus kuriphilus Yasumatsu, an insect native to China, was found in 2002 for the first time in Europe, and specifically in North western Italy (Cuneo province). The cynipid lays eggs into dormant buds and, in the following year, causes the development of galls on leaves, sprouts and inflorescences, due to the feeding activity of larvae. The wasp has an effect both on growth and yield of the tree. Complete resistance to D. kuriphilus was recently found in the hybrid Bouche de Betizac (C. sativa × C. crenata) and the genetic bases regulating this resistance are being investigated. Accessions of the cultivars Marrone (susceptible) and Bouche de Betizac (resistant) were subjected to an intensive attack of D. kuriphilus, with the purpose of getting infested buds to be examined at different stages of development of larvae. At budburst and just afterwards (March-April) buds were collected for the extraction and isolation of mRNA. cDNA was obtained by reverse transcription and analysed using the differential display technique. Two protocols, differing for the primer design, were applied and the results showed that 13 mer primers in combination with one-base anchored oligo-dT primers produced the best scorable profiles. Differentially expressed bands were cloned, sequenced and blasted with sequences deposited in NCBI and TIGR databases; putative genes were identified. The results showed that early activity of larvae in susceptible genotypes particularly influences the expression of genes involved in differentiation and nourishing; other genes found differentially expressed in infested tissues are involved in the plant response to external stimuli.