State of the spread of the exotic parasitoid wasp Leptopilina japonica tracking the route of its invasive host fly Drosophila suzukii in France

Highbush blueberry is a crop native to the northeast USA that has been domesticated for about 100years. This study compared the susceptibility of wild and domesticated/cultivated highbush blueberries to an invasive frugivorous pest, the spotted wing drosophila (Drosophila suzukii). We hypothesized that: 1) cultivated fruits are preferred by D. suzukii for oviposition and better hosts for its offspring than wild fruits; and, 2) wild and cultivated fruits differ in physico-chemical traits. Fruits from wild and cultivated blueberries were collected from June through August of 2015 and 2016 from 10 to 12 sites in New Jersey (USA); with each site having wild and cultivated blueberries growing in close proximity. The preference and performance of D. suzukii on wild and cultivated blueberries were studied in choice and no-choice bioassays. In addition, we compared size, firmness, acidity (pH), total soluble solids (°Brix), and nutrient, phenolic, and anthocyanin content between wild and cultivated berries. In choice and no-choice bioassays, more eggs were oviposited in, and more flies emerged from, cultivated than wild blueberries. Cultivated fruits were 2x bigger, 47% firmer, 14% less acidic, and had lower °Brix, phenolic, and anthocyanin amounts per mass than wild fruits. Levels of potassium and boron were higher in cultivated fruits, while calcium, magnesium, and copper were higher in wild fruits. These results show that domestication and/or agronomic practices have made blueberries more susceptible to D. suzukii, which was associated with several physico-chemical changes in fruits. Our study documents the positive effects of crop domestication/cultivation on an invasive insect pest.

Indigenous parasitoids (Hymenoptera) attacking Anastrepha fraterculus and Ceratitis capitata (Diptera: Tephritidae) in native and exotic host plants in Northwestern Argentina

The Spotted Wing Drosophila (SWD), Drosophila suzukii Matsumura, an invasive pest species in Europe and the Americas, is able to feed and reproduce on numerous fruit crops and a wide range of wild host plants. SWD is thought to overwinter outside of agricultural fields in forests and hedges. To identify overwintering sites and early spring oviposition hosts, traps were installed in forests. In spring 2015, traps in the canopy of pine trees parasitized by mistletoe, Viscum album subsp. laxum, captured significantly more SWD than traps in pine trees without mistletoe. We found SWD females with ripe eggs coinciding with ripening and ripe mistletoe berries. We investigated whether mistletoe may serve as a host for SWD. Under laboratory conditions, SWD developed from egg to adult in mistletoe berries. More adults emerged from wounded berries. Females were observed to feed on berries and survived up to eight days without other food. A few adults emerged from wild mistletoe berries. To understand the attraction of SWD to parasitized trees, we analyzed the volatile organic compounds (VOCs) collected from the headspace of mistletoe berries by GC–MS and identified the main components. Thirty-two VOCs were found. Wounded and unwounded berries differed significantly in the quantity of 11 VOCs emitted. The odor spectrum showed many similarities to other typical berry odors. The combination of field surveys and laboratory assays identified a new reproduction host for SWD in spring. This host plant may help SWD to withstand the bottleneck period for survival in winter and spring.

Native to southeast Asia, the spotted-wing drosophila (Drosophila suzukii (Matsumura); Diptera: Drosophilidae) has become a major pest of small fruits in the Americas and Europe. Field studies were conducted over a two-year period (2015–2016) in cultivated highbush blueberry (Vaccinium corymbosum Linnaeus; Ericaceae) fields and adjacent non-crop habitats containing wild blueberries in New Jersey (United States of America). We tracked seasonal changes in D. suzukii adult abundance and fruit infestation throughout the ripening period (June–August). In both years, D. suzukii adult counts post-harvest were generally higher in traps located in non-crop habitats compared with those located in highbush blueberry fields. Wild and cultivated fruits synchronised in maturation, and the numbers of eggs laid and of emerged adults in both fruit types were comparable for most of the season, although sometimes these numbers were higher in wild fruits post-harvest. Overall, immature success (measured as the per cent egg-to-adult survival) was also mostly higher in wild than in cultivated fruits. Altogether, these studies document that non-crop habitats, and wild hosts therein, are used by D. suzukii during fruit ripening and may serve as potential sources of infestation to nearby highbush blueberry fields. Hence, methods that reduce D. suzukii populations in non-crop habitats may help manage this pest in neighbouring highbush blueberries.

Apple is one of the staple fruits worldwide which are a good source of mineral nutrients. However, little is known about genetic variation for mineral nutrition in apple germplasm. In this study, the calcium and zinc contents in mature fruits of 378 apple cultivars and 39 wild relatives were assessed. Mineral concentrations were quantified using flame atomic absorption spectroscopy (FAAS). Both calcium and zinc accumulation showed great variation among accessions tested. Overall, wild fruits were significantly richer in zinc than cultivated fruits, while the average concentration of calcium was similar between cultivated and wild fruits. The difference in zinc concentration between wild and cultivated fruits may be an indirect result of artificial selection on fruit characteristics during apple domestication. Moreover, calcium concentration in fruit showed a decreasing trend throughout fruit development of apple, while zinc concentration in fruit displayed a complex variation pattern in the late stages of fruit development. The finding of a wild genetic variation for fruit calcium and zinc accumulation in apple germplasm could be helpful for future research on genetic dissection and improvement of calcium and zinc accumulation in apple fruit. © 2017 Society of Chemical Industry.

Simple SummaryDrosophila suzukii has become a globally invasive pest of thin-skinned berries and stone fruits such as strawberries, blueberries, raspberries, blackberries, and cherries. D. suzukii has caused severe economic losses to the fruit industries in more than 30 countries and has been listed as an important quarantine pest in many countries around the world. To better understand the ecology of this invasive pest for its effective management, it is essential to investigate the occurrence of D. suzukii and its wild host fruits and natural enemies in its native range. Here, we report the occurrence of D. suzukii and its wild host fruits and associated parasitoids in Liaoning, Northeast China for the first time. Four species of wild berries from non-crop habitats were found infested by D. suzukii, and two species of parasitoids (Leptopilina japonica and Asobara japonica) were discovered. Over the survey period from June to October, D. suzukii adult populations increased and peaked in August, and then declined until it was no longer detectable in October.Spotted-wing drosophila, Drosophila suzukii (Matsumura), is a worldwide quarantine pest that is currently undergoing a rapid range expansion in the Americas, Europe, and parts of Africa. It feeds and breeds on soft-skinned fruits such as raspberries, blueberries, and cherries, and can cause significant economic losses to fruit production. This study investigated the occurrence of D. suzukii and its wild host fruits and parasitoids in Liaoning, Northeast China for the first time. Sentinel traps were used to monitor D. suzukii adults, and suspected fruits were collected weekly in four different locations (Wafangdian, Faku, Fengcheng, and Shenyang). The results showed that D. suzukii were distributed in the sweet soft-skinned fruit-production areas of Liaoning, and raspberry was the most infested fruit. During the field survey, four species of wild berries from non-crop habitats were found infested by D. suzukii, and two species of parasitoids (Leptopilina japonica and Asobara japonica) were collected. D. suzukii adult-population dynamics throughout the survey period (June to October) were similar in different survey locations; adult fly populations increased and peaked in August, and then declined until the fly was no longer detectable in October.

Drosophila suzukii (Matsumura) (Diptera: Drosophilidae) is an invasive vinegar fly that attacks a large variety of soft fruits including wild blueberries in Maine. Wild blueberry fields in Maine are commonly surrounded by woodland edges that contain wild fruit. These edges are important refugia as they provide the fly with needed shade and moisture during the hottest parts of the day. The wild fruit in these wooded edges are also potential alternative hosts for D. suzukii. We surveyed wild fruit along blueberry fields to determine the types of fruit present and measured D. suzukii infestation levels in surveyed fruit. We also measured the number of adult D. suzukii along field edges and the level of infestation in the wild blueberry crop. Drosophila suzukii was found in nine out of seventeen surveyed wild fruit species along field edges. Our results suggest a correlation between wild fruit infestation levels and adult fly densities in the crop fields. Blueberry fields with higher levels of wild fruit infestation also showed higher levels of adult D. suzukii trap captures in the commercial blueberry fields. These wild fruit hosts may allow D. suzukii to increase its population abundance prior to moving into commercial blueberry fields.

Drosophila suzukii (Matsumura) (Diptera: Drosophilidae), commonly known as spotted-wing Drosophila (SWD), is an invasive insect pest threatening the economy of many small fruit farms in the Americas and Europe. Biological control using parasitoids is a promising strategy for improving the sustainable management of SWD. To use the parasitoids as biocontrol agents, recognizing and understanding the presence and preference of North American native parasitoids and their local adaptation is necessary. We conducted 2 season-long field explorations of North American native parasitoids of SWD during 2021 and 2022 at major blueberry-producing locations in southeast GA, USA. A total of 371 parasitoids of Drosophila were collected using fruit-baited sentinel traps and classified into 3 families: Figitidae, Pteromalidae, and Diapriidae. Leptopilina boulardi (Hymenoptera: Figitidae) and Pachycrepoideus vindemmiae (Hymenoptera: Pteromalidae) were the most abundant species. The abundance of parasitoids was higher during the peak blueberry ripening period through the end of the harvest season compared to all other phenological stages. Out of the North American native parasitoids of SWD that we collected, Pachycrepoideus vindemmiae successfully parasitized SWD in its natural habitat, and L. boulardi only parasitized SWD larvae at a low rate of 7% in the laboratory, but it failed to emerge from all the parasitized SWD. Ultimately, we found that the existing North American native parasitoids were inadequate to suppress the SWD in these locations. Planned intervention with the classical release of Asian native specialist parasitoids in addition to the existing SWD management approaches was deemed necessary in these areas.

Following introduction of Halyomorpha halys in Europe and North America, a concerted effort has been made to characterize host–parasitoid interactions involving H. halys. Yet, it is unclear whether the reported low parasitism in the field is due to the rejection of H. halys by native parasitoids, or the inability of larvae to develop. To determine whether native and exotic pentatomids are equally exploited by native parasitoids in the introduced range of H. halys, sentinel stink bug (native and exotic) egg masses were exposed in different habitats and the incidence of parasitism was determined by rearing and DNA-based approaches. Parasitism estimates were always lower with rearing compared to the molecular method. Egg masses of both native and exotic host species were equally likely to be attacked under natural conditions, supporting the idea that H. halys represents an evolutionary trap for native parasitoids. Lack of parasitoid emergence from H. halys eggs is probably not due to native parasitoids rejecting this host, but rather due to the inability of larvae to complete development. The frequent parasitization of H. halys by native parasitoids highlights the possibility of interspecific interactions with natural enemies considered for introduction as part of biological control programme (e.g. Trissolcus japonicus). Oviposition in eggs of the unsuitable H. halys host by native parasitoid may also have population-level consequences for both parasitoids (e.g. reduced population size, shifts in parasitoid community composition) and pentatomids (e.g. competition with H. halys, deceased population regulation by parasitoids). These effects should be considered when developing biological control strategy for H. halys.

Drosophila suzukii Matsumura (Diptera: Drosophilidae), also known as spotted wing drosophila (SWD), is an important pest that damages various wild and cultivated soft fruits worldwide, especially in the Northern Hemisphere. In Brazil, it occurs mainly in the subtropical climates of the southern and southeastern regions. However, SWD has also been sporadically found in the central region of the country in the natural vegetation of the tropical Brazilian Savanna. In this study, we investigated the occurrence of SWD at the northern limit of its range in South America - the central region of Brazil - by monitoring an established drosophilid community in an orchard located in the Brazilian Federal District. We also investigated the current geographical distribution of this pest in Brazil and its potential geographical distribution using species distribution models under two different future shared socioeconomic pathways scenarios (2040 and 2060, optimist and pessimist). Twenty drosophilid species were detected among the 6,396 captured specimens, most of which are exotic in the Neotropical region. The fly community greatly fluctuated throughout the year, and the highest abundance of SWD (3.5% relative abundance and 1.38 flies/trap/day) was recorded in April during the rainy season. Potential distribution models indicate that suitable areas for SWD spread will decrease in the south and southeast but increase in the central region of Brazil. We recommend continuous SWD monitoring and improving bioclimatic forecast models for mitigating damage to local fruit production.

The fruit of indigenous, cultivated, and naturalized exotic plants was sampled in Kenya to determine the geographical and host plant distributions of the fruit fly pests Ceratitis anonae (Graham), Ceratitis cosyra (Walker), Ceratitis fasciventris (Bezzi), and Ceratitis rosa Karsch. In 1997, cultivated and wild fruit were sampled on the Kenya coast to determine seasonal patterns of host use by C. cosyra and C. rosa. From 1999 to 2004, the sampling effort was expanded to forested areas of the central and western highlands and to all fruit-infesting tephritids. Together, the four pest tephritid species were reared from 5.1% of 3,794 fruit collections, the latter making up 116 families and 882 species of host plants. C. anonae, C. cosyra, C. fasciventris, and C. rosa were reared throughout Kenya, from 14, 9, 30, and 28 plant species, respectively. Fifty-two of these plants represented previously unknown hosts for one or more of the tephritids. C. anonae was restricted to habitats west of the Gregory Rift Valley. C. fasciventris was found in western and central Kenya, but it was not reared from coastal fruit collections. C. rosa occurred at the coast and in central highland fruit. We provide evidence for the recent introduction of C. rosa into the central highlands. Only C. cosyra was found in habitats located in all three of the major regions sampled. Although distributed over a wider geographic area than the other species, C. cosyra had a markedly restricted host range. On the coast, C. cosyra used wild fruit, primarily Sclerocarya birrea (A. Rich.) Hochst. (Anacardiaceae), as hosts when mango was not fruiting. C. rosa was absent from our mango samples but attacked common guava and wild fruit species. Overall, C. anonae, C. fasciventris, and C. rosa had similar host profiles, but each also had unique hosts in which infestations were usually heavy. Members of the Sapotaceae and Annonaceae were the most important wild hosts of these three species. Within these families, host fruit were partitioned among these tephritid species and the Mediterranean fruit fly, Ceratitis capitata (Wiedemann). The availability of wild host fruit, sometimes supplemented by naturalized invasive plants or cultivated fruit, provided for year-round breeding of C. anonae and C. fasciventris, whereas indigenous fruit were sufficient for breeding of C. rosa and C. cosyra during most of the year. Opiine braconids were reared from all four species of Ceratitis.

Two species of larval parasitoids of the globally invasive fruit pest, Drosophila suzukii (Diptera: Drosophilidae), Leptopilina japonica, and Ganaspis brasiliensis (both Hymenoptera: Figitidae), were detected in British Columbia, Canada in 2016 and 2019, respectively. Both are presumed to have been unintentionally introduced from Asia; however, the extent of their establishment across different habitats with diverse host plants used by D. suzukii was unclear. In addition, there was no knowledge of the temporal dynamics of parasitism of D. suzukii by these two parasitoids. To address these gaps, we repeatedly sampled the fruits of known host plants of D. suzukii over the entire 2020 growing season in British Columbia. We documented the presence of L. japonica and G. brasiliensis and estimated the apparent percentage of D. suzukii parasitized among host plant species. Across a large region of southwestern British Columbia, both L. japonica and G. brasiliensis were found to be very common across a variety of mostly unmanaged habitats over the entire course of the season (May-October) in the fruits of most host plants known to host D. suzukii larvae. Parasitism of D. suzukii was variable (0-66% percent parasitism) and appeared to be time-structured. Our study demonstrates that the close association between the two larval parasitoids and D. suzukii that exists in Asia has evidently been reconstructed in North America, resulting in the highest parasitism levels of D. suzukii yet recorded outside of its area of origin.

Potential competitive outcomes among three solitary larval endoparasitoids as candidate agents for classical biological control of Drosophila suzukii

Aspects of the biology and reproductive strategy of two Asian larval parasitoids evaluated for classical biological control of Drosophila suzukii

Fruit flies are pests of economic importance in West Africa due to their quarantine status and losses recorded in fruits and vegetables. Before the introduction of exotic species of parasitoids against any exotic fruit fly species, it is fundamental to first determine the presence and monitor the native parasitoid species. This work was carried out in Casamance (Senegal), during the rainy season of 2010, with sampling of 5191 fruits from 22 plant species. Seven species of parasitoids (all Braconidae) were recorded and reared from six fruit species. The parasitoids included Fopius caudatus (Szepligeti), F. silvestrii (Wharton), F. desideratus (Bridwell), Diachasmimorpha fullawayi (Silvestri), D. carinata (Szepligeti), Psyttalia cosyrae (Wilkinson) and P. concolor (Szepligeti). The most abundant species was F. caudatus (63.97%). The overall mean parasitism rate observed in all samples was 2.4 ± 1.3 %. Ceratitis cosyra (Walker) (77%) was the host fly most commonly reared from fruits yielding parasitoids incl...