The Diversity of Bacteria Associated with the Invasive Gall Wasp Dryocosmus kuriphilus, Its Galls and a Specialist Parasitoid on Chestnuts

Dryocosmus kuriphilus (Hymenoptera: Cynipidae) induces galls on chestnut trees, which results in massive yield losses worldwide. Torymus sinensis (Hymenoptera: Torymidae) is a host-specific parasitoid that phenologically synchronizes with D. kuriphilus. Bacteria play important roles in the life cycle of galling insects. The aim of this research is to investigate the bacterial communities and predominant bacteria of D. kuriphilus, T. sinensis, D. kuriphilus galls and the galled twigs of Castanea mollissima. We sequenced the V5–V7 region of the bacterial 16S ribosomal RNA in D. kuriphilus, T. sinensis, D. kuriphilus galls and galled twigs using high-throughput sequencing for the first time. We provide the first evidence that D. kuriphilus shares most bacterial species with T. sinensis, D. kuriphilus galls and galled twigs. The predominant bacteria of D. kuriphilus are Serratia sp. and Pseudomonas sp. Furthermore, the bacterial community structures of D. kuriphilus and T. sinensis clearly differ from those of the other groups. Many species of the Serratia and Pseudomonas genera are plant pathogenic bacteria, and we suggest that D. kuriphilus may be a potential vector of plant pathogens. Furthermore, a total of 111 bacteria are common to D. kuriphilus adults, T. sinensis, D. kuriphilus galls and galled twigs, and we suggest that the bacteria may transmit horizontally among D. kuriphilus, T. sinensis, D. kuriphilus galls and galled twigs on the basis of their ecological associations.

A new species of oak gall wasp (Hymenoptera: Cynipidae, Cynipini) from Turkey

A new species of the genus Andricus Hartig, 1840 (Cynipidae: Cynipini) is described from Burdur province in Turkey: Andricus arslani Azmaz & Katılmış sp. n. sexual generation. The new species induce galls on Quercus cerris L. belonging to section Cerris. SEM images, photos of the host galls, and data on the diagnosis, distribution, and biology of the new species are provided.

A new genus of Neotropical oak gall wasp, Prokius Nieves-Aldrey, Medianero & Nicholls, gen. nov. (Hymenoptera: Cynipidae: Cynipini), with description of two new species from Panama

A new genus, Prokius Nieves Aldrey, Medianero & Nicholls, gen. nov., and two new species of oak gall wasps (Hymenoptera: Cynipidae: Cynipini), Prokius cambrai Medianero & Nieves-Aldrey sp. nov. and Prokius lisethiae Medianero & Nieves-Aldrey sp. nov., are described from adults reared from galls on Quercus bumelioides Liebm (Fagaceae, sect. Quercus, white oaks) collected in Panama. The new genus is phylogenetically and morphologically close to Dros Kinsey and forms part of a large clade that includes species from several other genera that appear to require revision, including Andricus Hartig and Phylloteras Ashmead. Molecular and morphological data, diagnostic characters, gall descriptions, distribution and biological data of the new genus and the new species are given. This new genus represents the fourth recently described genus of Cynipidae endemic to the Neotropical region.

Local-scale dispersal patterns and susceptibility to Dryocosmus kuriphilus in different Castanea species and hybrid clones: insights from a field trial

The chestnut gall wasp Dryocosmus kuriphilus is a major insect pest affecting chestnut trees worldwide. Medium and long-term control of this pest can be improved by using resistant or less susceptible cultivars and hybrid clones. In addition, little is known about the local patterns of dispersal of the pest. We obtained data from trees of 3 chestnut species and 27 hybrid clones in a field trial in NW Spain with the aim of evaluating the susceptibility of the material to the gall wasp and identifying possible drivers of local spatial dispersal. In the first 3 years of the invasion by D. kuriphilus, the number of trees attacked and the number of galls on each tree were spatially clustered. Tree height significantly predicted both variables, suggesting that gall wasps may use visual cues to locate suitable host trees, at least in the early stage of invasion. Assessment of the susceptibility of hybrid clones/pure species must take concurrent indicators of infestation levels into account. We suggest the use of indices involving galls on shoots because these enable good assessment of the damage to chestnut trees. The study findings add to existing knowledge on the susceptibility of hybrid chestnut clones. We report, for the first time, two hybrid clones resistant to the pest and one hybrid clone which exhibited consistently low values for all of the indicators of infestation level. The results have important implications regarding selection of plant material for use in afforestation in Spain, where the current high rate of chestnut planting is expected to continue.

Population Dynamics and Tree Damage of the Invasive Chestnut Gall Wasp, Dryocosmus kuriphilus, in Its Southernmost European Distributional Range

The invasive chestnut gall wasp (CGW), Dryocosmus kuriphilus, the worst pest of chestnut cultivation, has spread worryingly throughout Europe in less than 20 years. Despite the great concern around this pest, little is known about the status in its southernmost distribution in continental Europe. We assessed spatio-temporal patterns in the population dynamics, phenology and tree damage caused by CGW in southern Spain. Likewise, the relationship between these variables and thermal trends was evaluated. We found strong variation in the population dynamics and flight phenology among localities and over time, which were highly influenced by changes in thermal regimes. Specifically, warmer localities and vegetative periods promoted higher population densities, a partial increase in the survival of immature stages, and advanced flight activity. Moreover, tree damage evolved differently over time in each locality, which suggests that local conditions may determine differences in damage evolution. Our findings evidence that great spatio-temporal variability in the CGW populations takes place across invaded areas in its southernmost European distributional range. Although control mechanisms have been introduced, implementation of further control and management measures are critical to cope with this main threat for the chestnut industry and to prevent its spread to nearing chestnut-producing areas.

Ophelimus bipolaris sp. n. (Hymenoptera, Eulophidae), a New Invasive Eucalyptus Pest and Its Host Plants in China

Eucalyptus species have become one of the most commonly planted trees worldwide, including China, due to their fast growth and various commercial applications. However, the productivity of Eucalyptus plantations has been threatened by exotic invasive insect pests in recent years. Among these pests, gall inducers of the genus Ophelimus of the Eulophidae family are among the most important invasive species in Eucalyptus plantations. We report here for the first time the presence of a new invasive Eucalyptus gall wasp, Ophelimus bipolaris sp. n., in Guangzhou, China, which also represents the first species of the genus reported from China. The identity of the new species was confirmed by an integrative approach combing biological, morphological and molecular evidence. The new species is described and illustrated. This wasp induces galls only on the leaf blade surface of four Eucalyptus species: E. grandis, E. grandis × E. urophylla, E. tereticornis and E. urophylla. Our preliminary observation showed that O. bipolaris could complete a life cycle on E. urophylla in approximately 2 months under local climatic conditions (23.5–30 °C). Considering the severe damage it may cause to Eucalyptus production, further investigations of its biology and control are urgently needed in China.