First record of the invasive pest <Emphasis Type="Italic">Drosophila suzukii</Emphasis> in Ukraine indicates multiple sources of invasion

Drosophila suzukii, commonly known as the spotted-wing Drosophila, is an invasive polyphagous fruit pest, which has emerged as a global threat to agriculture in the Americas and in Europe. Due to the rapid spread, great economic losses and its pest behavior, D. suzukii represents a powerful model for invasion biology and pest management studies. However, its current European distribution, invasion routes and levels of genetic diversity in populations of D. suzukii are poorly understood. We present the first report of D. suzukii from Ukraine, with the invasion likely occurring close to 2014. The pattern of genetic variation at cytochrome oxidase I among D. suzukii populations from Europe, USA and Asia reveals comparatively high genetic diversity in the Ukrainian population of this pest species, suggesting a complex invasion scenario from multiple sources. Further monitoring patterns of genetic variation across space and time, to better understand the invasion routes of this invasive insect pest, will be an essential part for developing successful pest management strategies.     

Biological invasion of European tomato crops by Tuta absoluta: ecology, geographic expansion and prospects for biological control

The tomato leafminer Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) is a devastating pest of tomato originating from South America. After its initial detection in eastern Spain in 2006, it rapidly invaded various other European countries and spread throughout the Mediterranean basin. If no control measures are taken, then the pest can cause up to 80–100% yield losses in tomato crops in recently invaded areas and may pose a threat to both greenhouse and open-field tomato production. The exceptional speed and extent of T. absoluta invasion have called for studies documenting its biology and ecology, while indicating an urgent need for efficient and sustainable management methods. The development of approaches to manage T. absoluta would be facilitated through a detailed revision of information on this pest in its area of origin. This review combines information on the invasion by T. absoluta, its ecology, and potential management strategies, including data that may help the implementation of efficient biological control programs. These programs, together with a variety of other management tactics, may allow efficient integrated pest management of T. absoluta in Europe and Mediterranean Basin countries.     

A first inference of the phylogeography of the worldwide invader Xylosandrus compactus

Native to Southeastern Asia, the ambrosia beetle Xylosandrus compactus is invasive worldwide. Its invasion is favoured by its cryptic lifestyle, symbiosis with a fungus that facilitates a broad range of host plants, and predominant sib-mating reproduction. X. compactus invaded Africa more than a century ago and the Americas and Pacific Islands in the middle of the twentieth century. It was not detected in Europe before 2011, when it was first reported in Italy before quickly spreading to France, Greece and Spain. Despite the negative environmental, agricultural and economic consequences of the invasion of X. compactus, its invasion history and main pathways remain poorly documented. We used COI and RAD sequencing to (i) characterise the worldwide genetic structure of the species, (ii) disentangle the origin(s) of the non-native populations on the three invaded continents and (iii) analyse the genetic diversity and pathways within each invaded region. Three mitochondrial lineages were identified in the native range. Populations invading Europe and the American-Pacific region originated from the first lineage and were only slightly genetically differentiated at nuclear SNP markers, suggesting independent introductions from close sources in or near Shanghai, ca. 60 years apart. Populations invading Africa originated from the second lineage, likely from India or Vietnam.

     

Identification of attractive blend for spotted wing drosophila, <Emphasis Type="Italic">Drosophila suzukii</Emphasis>, from apple juice

Drosophila suzukii, commonly known as the spotted wing drosophila (SWD), is an exotic fruit fly from Southeast Asia that was introduced to the temperate regions of North America and Europe in 2008. It attacks a wide variety of fruits and has become a devastating pest of soft-skinned fruit crops. Due to the rapid spread of SWD across the newly invaded continents, fresh fruit markets have a zero-tolerance policy regarding D. suzukii infestation. Specific and efficient D. suzukii detection tools are urgently needed so that farmers can deliver timely management interventions to meet market demands. Since SWD is known to be attracted to damaged and rotting fruits, headspace volatiles from fresh and fermented apple juices were collected and analyzed by gas chromatography–mass spectrometry. Special attention was given to the compounds produced and/or enriched during the fermentation process. After performing a series of laboataory and field tests, we identified a quinary blend, which is more efficient and selective for D. suzukii than the currently standard apple cider vinegar and commercially available SWD lure under field conditions. Identification of SWD attractant will help growers accurately detect D. suzukii adult infestations in orchards, thereby allowing for timely pest management interventions while reducing conventional insecticidal usage to protect our crops, environment, and ecosystem.     

Rapid harvest schedules and fruit removal as non-chemical approaches for managing spotted wing Drosophila

Spotted wing Drosophila, Drosophila suzukii (Matsumura) (Diptera: Drosophilidae), has caused significant economic losses to small fruit and berry growers throughout the USA and Europe since its invasion. This pest can lay many eggs over its lifetime within ripening and ripe berries, causing yield loss and the risk of fruit contamination. Zero tolerance for this pest has led to increased use of broad-spectrum insecticides to control it, which are costly and pose many other sustainability and pest management concerns. There is an urgent need to evaluate management strategies that can decrease reliance on chemical controls and mitigate economic losses. Over two growing seasons, we compared harvest schedules for their effect on infestation by D. suzukii, revealing that fruit harvested every 1 or 2 days had significantly fewer D. suzukii larvae than a 3-day harvest schedule. Furthermore, we found that yield per unit effort was highest on a 2-day schedule. Sanitation of the crop is another important component of a successful integrated pest management program, and we found that bagging infested waste berries killed 99% of larvae after 32 h, with higher fruit temperatures in clear bags than white or black bags. In combination, these methods can reduce the effects of this invasive pest on raspberry production. This study will provide guidance to growers on culturally based IPM tactics to decrease reliance on chemical management.     

Sterile insect technique and <Emphasis Type="Italic">Wolbachia</Emphasis> symbiosis as potential tools for the control of the invasive species <Emphasis Type="Italic">Drosophila suzukii</Emphasis>

Drosophila suzukii, a vinegar fly originated from Southeast Asia, has recently invaded western countries, and it has been recognized as an important threat of a wide variety of several commercial soft fruits. This review summarizes the current information about the biology and dispersal of D. suzukii and discusses the current status and prospects of control methods for the management of this pest. We highlight current knowledge and ongoing research on innovative environmental-friendly control methods with emphasis on the sterile insect technique (SIT) and the incompatible insect technique (IIT). SIT has been successfully used for the containment, suppression or even eradication of populations of insect pests. IIT has been proposed as a stand-alone tool or in conjunction with SIT for insect pest control. The principles of SIT and IIT are reviewed, and the potential value of each approach in the management of D. suzukii is analyzed. We thoroughly address the challenges of SIT and IIT, and we propose the use of SIT as a component of an area-wide integrated pest management approach to suppress D. suzukii populations. As a contingency plan, we suggest a promising alternative avenue through the combination of these two techniques, SIT/IIT, which has been developed and is currently being tested in open-field trials against Aedes mosquito populations. All the potential limiting factors that may render these methods ineffective, as well as the requirements that need to be fulfilled before their application, are discussed.     

Phenology,life table analysis and temperature requirements of the invasive brown marmorated stink bug,Halyomorpha halys,in Europe

The invasive Halyomorpha halys was accidentally introduced into Switzerland around 2004 and has recently established in the neighbouring countries of France and Italy. To better understand the population dynamics of this pest in Europe, the phenology, reproductive biology and temperature requirements of Swiss H. halys populations were investigated. Overwintered adults became active in April, but peak oviposition was not observed before early July. Individual females laid on average 79 eggs (maximum of 160). The oviposition period lasted from mid-June to end of September. Eggs laid in August and September did not result in offspring due to the low temperatures in autumn. Under natural fluctuating temperatures, development from egg to adult lasted between 60 and 131 days. The first new generation of adults did not occur before mid-August when the photoperiod was already below 15 h, which likely initiated diapause and suppressed the reproductive activity of new generation adults. Under controlled conditions of 20, 25 and 30 °C, Swiss H. halys populations developed within 75.8, 42.3 and 33.2 days from egg to adult, respectively. No development was possible at or below 15 and at or above 35 °C. The number of degree days required for completion of development from egg to adult was 588.24 DD. Under semi-natural conditions, total mortality of Swiss H. halys populations was 86.7 % with a net reproductive rate of 5.69, indicating growing populations. In Switzerland, H. halys is univoltine, but if it continues to spread into the Mediterranean area two generations per year could be expected.     

Pheromone detection of the introduced forest pest Megaplatypus mutatus (=Platypus mutatus) (Chapuis) (Platypodinae, Curculionidae) in Italy

Megaplatypus mutatus (Chapuis) (=Platypus mutatus), an ambrosia beetle native to South America, attacks standing live trees of a wide range of forest and fruit tree species, and it is particularly damaging to commercial poplar plantations. In 2000, M. mutatus was observed for the first time in Italy, in the province of Caserta, near Naples. The development of a pheromone-based monitoring system, for detecting the spread and for managing M. mutatus infestations, is an important goal for both European and South American control and surveillance programs. Using a three component pheromone blend developed in Argentina into commercial funnel traps we were able to asses the level of dispersion of this pest in the Italian Campania region. Insects were captured in all the plantations suspected of being infested based on the presence of active parental and larval galleries. We also provide the first report of the attack followed by completion of the life cycle of M. mutatus in European hazelnut, Corylus avellana L. (Betulaceae), an important nut species native to Europe and Western Asia.     

Large-scale spatial dynamics of <Emphasis Type="Italic">Drosophila suzukii</Emphasis> in Trentino,Italy

Drosophila suzukii (Diptera: Drosophilidae) is an invasive alien species devastating soft fruit crops in newly invaded territories. Little is known about the importance and potential of long-distance dispersal at a regional scale. The goal of this work is to investigate D. suzukii dispersal ability during different times of the season, and along an elevational gradient in a mountain valley in Trentino Province, Italy. We employed a mark–release–recapture strategy using protein markers. Flies were recaptured using fruit-baited traps. The protein-marked flies were positively identified using ELISA procedure. Additional microsatellite analyses were performed on D. suzukii collected during autumn at different elevations to characterize the population structure. Results suggest that a portion of the local D. suzukii population moves from low to high elevations during spring and summer and travels back to low elevations in autumn. Genetic analysis further revealed that samples collected during autumn at different elevations belong to the same population. These results show that D. suzukii are able to fly up to about 9000 m away from the marking point and that seasonal breezes likely facilitate long-distance movement. We suggest that these migrations have multiple functions for D. suzukii, including conferring the ability to exploit gradual changes of temperature, food, and ovipositional resources in spring and autumn, as well as to assist in the search for suitable overwintering sites in late autumn. Our findings help to unveil the complex ecology of D. suzukii in Italian mountainous regions and provide important clues for improving the efficacy of integrated pest management control techniques to combat this pest.     

The first records of the invasive pest Drosophila suzukii in the South American continent

This paper presents the first report of the occurrence of Drosophila suzukii (Diptera: Drosophilidae) in South America. Several samples were collected during various seasons in 2012 and 2013, and a significant number of individuals were obtained and identified. Based on the data recorded during each sampling campaign, including the locality, temperature, time of year, and number of individuals collected, several conclusions were drawn about the development of this invasion in southern Brazil.     

From monospecific to mixed forest after fire?: An early forecast for the montane belt of Majella,Italy

Alternative hypotheses on post-fire successions of monospecific European beech (Fagus sylvatica L.) and black pine (Pinus nigra Arnold) forests are investigated. The research area is located in the centre of the Apennine montane belt, Italy and covers portions of the Roccamorice and Lettomanoppello municipalities within the Majella National Park. Temporal moderate-resolution (MODIS) and spatial mid-resolution (ASTER) imagery are combined for the assessment of the 2007-fire features. Tree seedlings were surveyed on the ground in post-fire forests and their unburnt equivalents during September 2008. The satellite imagery analysis provides records on spread, intensity, location and extent of the forest fires. The evidence suggests an abandoned farmland fire spreading secondarily uphill into the forests.     

Acute spread in France of an invasive pest, the horse chestnut leafminer Cameraria ohridella Deschka & Dimic (Lep., Gracillariidae)

The horse chestnut leafminer, Cameraria ohridella Deschka & Dimic (Lepidoptera, Gracillariidae) spread over the last 10 years from central Europe to western Europe and was observed for the first time in 2000 in the east of France and near Paris. This study presents the results of surveys carried out in France in 2001 to investigate the distribution and infestation level of the leafminer. One year after its first discovery, the moth was present in a large part of the country and for the first time has been observed in Paris. The spread of the moth is due mainly to natural dispersal and to passive dispersal by human activities.     

First report in Italy of the dusky sap beetle, Carpophilus lugubris, a new potential pest for Europe

Following a report submitted by a beekeeper to Istituto Zooprofilattico Sperimentale delle Venezie, in Padua province (Borgoricco, Veneto, NE Italy), the authors discovered in April 2011 several specimens of the dusky sap beetle Carpophilus lugubris Murray 1864 (Coleoptera, Nitidulidae) on the bottom board of some beehives. At a later time (May 2012), an isolated specimen was also collected within a Natural Reserve in Belluno province (Feltre, Veneto, NE Italy). These specimens represent the first known records of this species in Italy or Europe as a whole. This is also the first record of the species associated with beehives. This discovery led us to review the available bionomical and faunistic data for this widespread Nearctic and Neotropical species. C. lugubris is a recognized pest of corn, therefore is very important monitoring its possible dispersal into cornfields, beehives, and other agricultural regions of NE Italy and southern Europe over the next few years.     

Natural enemies of the South American moth, Tuta absoluta, in Europe, North Africa and Middle East, and their potential use in pest control strategies

The South American tomato leafminer, Tuta absoluta Meyrick (Lepidoptera: Gelechiidae), is an invasive Neotropical pest. After its first detection in Europe, it rapidly invaded more than 30 Western Palaearctic countries becoming a serious agricultural threat to tomato production in both protected and open-field crops. Among the pest control tactics against exotic pests, biological control using indigenous natural enemies is one of the most promising. Here, available data on the Afro-Eurasian natural enemies of T. absoluta are compiled. Then, their potential for inclusion in sustainable pest control packages is discussed providing relevant examples. Collections were conducted in 12 countries, both in open-field and protected susceptible crops, as well as in wild flora and/or using infested sentinel plants. More than 70 arthropod species, 20 % predators and 80 % parasitoids, were recorded attacking the new pest so far. Among the recovered indigenous natural enemies, only few parasitoid species, namely, some eulophid and braconid wasps, and especially mirid predators, have promising potential to be included in effective and environmentally friendly management strategies for the pest in the newly invaded areas. Finally, a brief outlook of the future research and applications of indigenous T. absoluta biological control agents are provided.     

The potential global distribution of <Emphasis Type="Italic">Chilo partellus</Emphasis>, including consideration of irrigation and cropping patterns

Chilo partellus is a major crop pest in Asia and Africa, and has recently spread to the Mediterranean region. Knowledge of its potential distribution can inform biosecurity policies aimed at limiting its further spread and efforts to reduce its impact in areas that are already invaded. Three models of the potential distribution of this insect have been published, each with significant shortcomings. We re-parameterized an existing CLIMEX model to address some parameter inconsistencies and to improve the fit to the known distribution of C. partellus. The resulting model fits the known distribution better than previous models, highlights additional risks in equatorial regions and reduces modelled risks in wet and extremely dry regions. We bring new insights into the role of irrigation in the potential spread of this invasive insect and compare its potential distribution with the present known distribution of its hosts. We also distinguish regions that are suitable for supporting persistent populations from those that may be at risk from ephemeral populations during favourable seasons. We present one of the first demonstrations of a new capability in CLIMEX to automatically estimate parameter sensitivity and model uncertainty. Our CLIMEX model highlights the substantial invasion risk posed by C. partellus to cropping regions in the Americas, Australia, China, Europe, New Zealand and West Africa. Its broad host range and reported impacts suggest that it should be a pest of significant concern to biosecurity agencies in these presently uninvaded regions.     

Die Verbreitung der Roßkastanien-Miniermotte Cameraria ohridella Desch. & Dimic (Lepid., Gracillariidae) in der Region Südtirol-Trentino

A survey on the present distribution of the horse chestnut leafmining moth, Cameraria ohridella Desch. & Dimic 1986, in Europe and in Italy is given: In Europe, within a period of 15 years, the leafminer – recently introduced into Central Europe – has settled in an area that spreads over 13 latitudinal and about 20 longitudinal degrees; in Northern Italy, an area of approximately 50,000 km² has been afflicted in the 5 years since the leafminer's introduction in South Tyrol and Julian Venetia in 1993.The development of the distribution in the region of South Tyrol and Trentino is shown: In the province of Bozen-South Tyrol, between 1995 and 1999 the moth has spread in all the three principal valleys (Eisacktal, Pustertal, Etschtal); in the Trentino province, first local attacks began only in 1998, near Trento and Riva, but spread over the entire Etschtal/Adige Valley in 1999. While in South Tyrol C. ohridella was introduced from the North (North Tyrol), the introduction into the Trentino occured from the South (Verona).At present the attacks in Trentino province are preponderantly low (resulting heavy only in the city of Trento and in Riva del Garda) and limited to altitudes ranging from 70 to 700 in. In South Tyrol, attacks are mainly heavy in altitudes ranging from 250 to 900/950 m, while they are low in the increasingly affected higher altitudes of 1,000 to 1,230 m. Numeric attack parameters are given to show attack intensities.The number of generations per year depends on the respective climatic conditions: in lower-altitudes, usually three generations develop in a year, but in higher altitudes (800 to 1,100 m) only two generations; in the climatically favoured area around the Lake Garda a (partial) fourth generation appears possible.The question of host plants (Aesculus sp., Acer sp.) and the larval parasitism of C. ohridella is discussed. The parasitism of the larvae, principally by Eulophidae (Hym., Chalcidoidea), was ascertained already in the first years of attack: In South Tyrol, 16 species of parasitoids appeared, and 8 in the Trentino province, but only two species were dominant: Minotetrastichus sp. and Pnigalio sp. The level of parasitism reached was low, comparable to other Central European countries.     

<Emphasis Type="Italic">Drosophila suzukii</Emphasis> flight performance reduced by starvation but not affected by humidity

Drosophila suzukii is widely studied because of its status as a global pest of berries and soft fruits. Environmental conditions and access to food resources impact the physiology and fitness of D. suzukii; these factors could also affect dispersal. Flight mills are a convenient tool for measuring and comparing the flight performance of insects. In this study, two experiments examined the effects of diet and humidity on D. suzukii flight performance using custom-built flight mills, and a third experiment compared the energy reserves of D. suzukii flown or not flown on flight mills. Over all flight assays, the median flight distance and duration were 27.16 m and 2.37 min, respectively, and the mean flight velocity was 0.18 m/s. The maximum flight distance and duration by an individual were 1.75 km and 2.35 h, respectively. Drosophila suzukii provisioned with blossoms, fruits, or standard laboratory diets flew farther distances and longer durations than starved flies. While starvation was associated with reduced flight performance, there were no observed differences between diet types. It remains unclear whether D. suzukii consistently use lipids, glycogen, sugar, or another energy source for flight because tethered individuals may not have flown enough to deplete energy reserves. Humidity did not affect flight performance of D. suzukii within a?~?2 h test period. These data indicate that most D. suzukii are likely to remain within limited area (e.g., within a field) but that some individuals can disperse long distances (field to field spread).     

Diversity and surge in abundance of native parasitoid communities prior to the onset of Torymus sinensis on the Asian chestnut gall wasp(Dryocosmus kuriphilus) in Slovenia,Croatia and Hungary

Since the rapid spread of the Asian chestnut gall wasp(ACGW) throughout south-east Europe in the last few years,the possibilities of its control have been increasingly investigated.Due to constraints in available suppression measures in forest stands,biological control is recognized as the most suitable action to lower the abundance of the new invasive pest.Torymus sinensis,as a specialized parasitoid chalcid wasp of ACGW,was introduced to suppress the pest in Italy in 2005,and later in Croatia,Hungary(2014) and Slovenia(2015).We investigated the native parasitoid complex associated with ACGW in Slovenia,Croatia and Hungary over 8 years of sampling.We found 41 species of native parasitoids,eight of which are the first records on ACGW in Europe,adding up to a total of 51 species known to parasitize ACGW.These findings represent a large complex of cynipid-parasitoid fauna.Moreover,the abundance of native parasitoid populations on ACGW have demonstrated a temporal surge between the invasion of a new alien host(ACGW) and the onset of its specialized parasitoid,T.sinensis.Our results indicate that the introduced parasitoid acts as a very successful biocontrol of ACGW,outcompeting native parasitoids.This outcome should be considered as beneficial through the maintenance of ecological balance in affected forest ecosystems.     

Spatial and temporal genetic variation of Drosophila suzukii in Germany

Native to Southeast Asia, the spotted wing drosophila (SWD), Drosophila suzukii Matsumura, rapidly invaded America and Europe in the past 20 years. As a crop pest of soft-skinned fruits with a wide range of host plants, it threatens the fruit industry worldwide, causing enormous economic losses. To control this invasive pest species, an understanding of its population dynamics and structure is necessary. Here, we report the population genetics and development of SWD in Germany from 2017–19 using microsatellite markers over 11 different sample sites. It is the first study that examines SWD’s genetic changes over 3 years compared to multiple international SWD laboratory strains. Results show that SWD populations in Germany are highly homogenous without differences between populations or years, which indicates that populations are well adapted, migrate freely, and multiple invasions from outside Germany either did not take place or are negligible. Such high genetic variability and migration between populations could allow for a fast establishment of the pest species. This is especially problematic with regard to the ongoing spread of this invasive species and could bear a potential for developing pesticide resistance, which could increase the impact of the SWD further in the future.

     

First evidence of deuterotokous parthenogenesis in the tomato leafminer, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae)

The tomato leafminer, Tuta absoluta (Lepidoptera: Gelechiidae), originates from South America and is now considered to be one of the most damaging invasive pests of tomatoes in the Mediterranean Basin countries of Europe and North Africa. The preventing pest mating control methods include: (1) the use of synthetic pheromones for male attraction and annihilation inside insecticide-containing traps; (2) mating disruption by saturating the atmosphere with sex pheromones which alter the ability of males to locate females; and (3) massive applications of sterile males to alter the overall reproductive success of the pest population. However, all these methods achieve only a poor success rate in controlling T. absoluta populations under greenhouse conditions. Sex pheromone management and sterile insect techniques are both based on an important biological trait: the insect must breed through sexual reproduction. Here, we report for the first time laboratory evidence of deuterotokous parthenogenesis, an asexual reproduction where both males and females are produced from unfertilized eggs. We discuss the consequences for T. absoluta control strategies.