Medfly eradication in California:

The impact of malathion-bait sprays (directed against medfly, Ceratitis capitata [Wiedemann]) on an endemic gall midge (Rhopalomyia californica Felt) and its parasitoids was investigated during 1982–83 in the south San Francisco Bay area of northern California. In a heavily sprayed area (Woodside), a population explosion of the midge was detected following 24 applications of malathion bait. The midge population reached levels ca. 90x greater than those observed in an adjacent unsprayed area (Jasper Ridge). In a moderately sprayed area (Portola Valley), the midge population increased as much as 5x that observed in the adjacent unsprayed area (Jasper Ridge), following 12 applications of malathion bait. In laboratory tests, the malathion bait was toxic to both the midge and its parasitoids. The major parasitoids were Torymus koebelei (Huber), Zatropis capitis Burks, Platygaster californica (Ashmead) and Mesopolobus sp. Population increases of the midge following malathion-bait sprays were attributed to destruction of parasitoids and other natural enemies of the midge. If the environmental impact of malathion-bait sprays is related to the number of applications (as suggested in this study), then it would be worthwhile to determine the appropriate bait-spray strategy for a given situation, so as to minimize adverse effects on nontarget species, yet insure suppression or eradication of medfly.

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Résumé L'impact des pièges tratiés au malathion (destinés à Ceratitis capitata Wiedem) sur Rhopalomyia californica Felt et ses parasitoïdes a été examiné en 1982–1983 dans le sud de la zone de la baie de San Francisco en Californie. Dans une zone fortement traitée (Woodside), une explosion de population a été décelée après 24 traitements. La population de R. californica a atteint des niveaux 90 fois supérieurs à ceux observés dans une zone contiguë non traitée (Jasper Ridge). Dans une zone modérément traitée (Portola Valley), avec 12 traitement, la population de R. californica a atteint jusqu'a 5 fois celle de Jasper Ridge. Au laboratoire, le piège à malathion a été toxique tant pour R. californica que pour ses parasitoïdes, dont les principaux étaient: Torymus koebelei (Huber), Zatropis capitis Burks, Platygaster californica(Ashmead) et Mesopolobus sp. L'accroissement de la population de C. capitata après traitement a été attribué à la destruction de parasitoïdes et d'autres ennemis naturels. Si l'effet su l'environnement du traitement est lié au nombre d'interventions (comme le suggère cette étude), alors cela vaudrait la peine de définir une stratégie de traitement appropriée à une situation donnée, de façon à minimiser les effets négatifs sur des espèces non visées, tout en assurant la suppression ou l'éradication de C. capitata.

     

Effects of large‐scale host plant addition and removal on parasitoid‐mediated associational resistance in the gall midge Asphondylia borrichiae

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Seasonal flight activity and genetic relatedness of Torymus species in Italy

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Rapid on-site identification of the biocontrol agent of the Asian chestnut gall wasp

In classical biocontrol programmes, a rapid and correct identification of the introduced antagonist is a key issue during both the release and establishment monitoring phases. It is often difficult to distinguish morphologically cryptic species or immature stages. An accurate diagnosis can now be provided by molecular diagnostic methods. Among the conventional and real-time PCR-based methods, loop-mediated isothermal amplification (LAMP) is a particularly suitable technique as it allows a rapid amplification of target DNA directly in the field. During the programme implemented in Italy against the Asian chestnut gall wasp (ACGW) Dryocosmus kuriphilus, we developed a real-time LAMP assay, combined with a simple DNA extraction method, for rapid in-field identification of larvae, pupae, and adults of the biocontrol agent, the parasitoid Torymus sinensis. Validation of the assay comprised adults as well as preimaginal stages of parasitoids obtained from ACGW galls collected from different localities. Results confirmed the effectiveness of the LAMP assay to rapidly and specifically identify the target parasitoid in the field. This assay will be a valuable tool for quick on-site checking of the parasitism rate.     

Bottom-up effects shift top-down community structure of the parasitoid guild that attacks Asphondylia borrichiae (Diptera: Cecidomyiidae) on Borrichia frutescens (Asteraceae)

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Two new species of Torymus Dalman, 1820 (Hymenoptera: Torymidae) parasitizing Celticecis japonica Yukawa and Tsuda, 1987 (Diptera: Cecidomyiidae) that induce leaf galls on Celtis species (Ulmaceae) in Japan

Torymus celticolus Matsuo sp. nov. and Torymus celtidigalla Matsuo sp. nov. (Hymenoptera: Torymidae) are described as parasitoids of larvae of Celticecis japonica Yukawa & Tsuda, 1987 (Diptera: Cecidomyiidae) that induce leaf galls on Celtis species (Ulmaceae) in Japan. A key to species of the genus Torymus known in Japan is provided.     

Host specialization is ancestral in Torymus (Hymenoptera,Chalcidoidea) cynipid gall parasitoids

The host range of parasitoids varies greatly among species: Some only parasitize one to a few hosts (specialists), while others parasitize multiple species or a variety of host types (generalists). The direction of most host range shifts in parasitoid groups, that is from generalist to specialist or, alternatively, from specialist to generalist, is unknown. To explore the origin of host range shifts, we studied a clade within the genus Torymus (Hymenoptera, Chalcidoidea) that includes both generalist and specialist parasitoids of Cynipidae (Hymenoptera). We analysed the phylogenetic relationships of the species of Torymus on the basis of two gene fragments (cox1 and ITS2) of 246 specimens and performed an ancestral state reconstruction of the specialist/generalist trait. Our results revealed the following: (a) The ancestral state of this group of Torymus is specialist, with the generalist state evolving through a loss of specialization. (b) The species Torymus cyaneus and Torymus flavipes both have a strong genetic structure, suggesting the existence of different biological identities. (c) There has been a host plant shift in the lineage(s) leading to Torymus rubi and Torymus bedeguaris from galls on Quercus to those on Rosaceae. (d) The alien species Torymus sinensis and the native European species Torymus notatus are phylogenetically closely related. (e) Speciation within Torymus was likely associated with the diversification of their cynipid hosts, which itself was driven by the dramatic changes in climate and vegetation that occurred during the Miocene.     

中国长尾小蜂属(膜翅目,长尾小蜂科)分类研究

研究了中国长尾小蜂属Torymus Dalman,记述3个中国新纪录种,提供了形态特征图,编制了中国长尾小蜂属分种检索表.研究标本保存在中国科学院动物研究所动物标本馆.     

Rearing,release and settlement prospect in Italy of <Emphasis Type="Italic">Torymus sinensis</Emphasis>, the biological control agent of the chestnut gall wasp <Emphasis Type="Italic">Dryocosmus kuriphilus</Emphasis>

Dryocosmus kuriphilus Yasumatsu (Hymenoptera: Cynipidae), is one of the most serious pests attacking chestnut trees. Recently it was incidentally introduced into Northwest Italy and it is now spreading throughout Europe. This pest was successfully controlled in Japan by introducing a parasitoid, Torymus sinensis Kamijo (Hymenoptera: Torymidae), from China’s mainland. Following this successful experience, the parasitoid was introduced into Italy from Japan. One year of preliminary studies led to a successful method of rearing imported galls with a synchronization between the parasitoid’s emergence and the presence of the target galls in the field. In two consecutive years, a total of 2,117 individuals were released in several sites covering most of the infested area. There are encouraging data about the settlement of the parasitoid and its synchrony with the host’s cycle: from about 64,000 host galls collected in the field over 200 T. sinensis were reared. The role of native parasitoids associated with the chestnut gall pest in its Italian distribution range is also discussed.     

Oxycephalomyia, gen. nov., and life history strategy of O. styraci comb. nov. (Diptera: Cecidomyiidae) on Styrax japonicus (Styracaceae)

A new genus Oxycephalomyia is described to contain the gall midge that was previously known as Asteralobia styraci (Shinji). Oxycephalomyia styraci, comb. nov., produces leaf vein galls on Styrax japonicus (Styracaceae). The adult of O. styraci is redescribed, and its full‐grown larva and pupa are described for the first time. The annual life cycle of the gall midge in northern Kyushu was clarified; the first instars overwinter in the galls on the host plant. However, the galls of O. styraci mature much later in the season than those of other gall midges with a similar life history pattern, and the durations of second and third larval instars are remarkably short. Such a life history pattern is considered to have an adaptive significance in avoiding larval parasitism, particularly by early attackers. The number of host axillary buds as oviposition sites decreased in bearing years and increased in off years, but there was no sign of oviposition site shortage even in bearing years, probably due to the low population density of the gall midge. An unidentified lepidopteran that feeds on galled and ungalled host buds and a Torymus sp. that attacks pupae of O. styraci were recognized as mortality factors of the gall midge.