Population genetics of the brown marmorated stink bug Halyomorpha halys in the early phase of invasion in South Tyrol (Northern Italy).

AbstractThe brown marmorated stink bug Halyomorpha halys is one of the most harmful invasive species in the world. Native to East Asia, this insect was introduced into North America in the 1990s and into Europe in the 2000s where it subsequently established and spread across the continent. Previous population genetic studies determined the invasion pathways at continental and national levels. However, information on the dynamics on a small-scale is currently scarce. Here we study the genetic diversity and population dynamics of H. halys in South Tyrol, a region in Northern Italy, since its arrival to its widespread establishment over a period of four years. By haplotyping 162 individuals from ten populations (including six previously published individuals) we found a high haplotype diversity in most populations with an increasing diversity across the different years. Most haplotypes were previously found in other regions of Northern Italy, providing evidence for migration from neighboring regions. However, the presence of four previously undescribed haplotypes as well as a haplotype previously found exclusively in Greece highlights additional long-distance dispersal across the continent. Phylogenetic analysis of the haplotypes found in South Tyrol showed that the majority of haplotypes clustered with haplotypes predominantly found in Japan. This suggests a potential recent introduction of H. halys individuals from Japan into Europe, and thus an additional invasion pathway that was previously unidentified

Occurrence of different Cacopsylla species in apple orchards in South Tyrol (Italy) and detection of apple proliferation phytoplasma in Cacopsylla melanoneura and Cacopsylla picta: (Hemiptera: Psylloidea)

Preventing the diffusion of phytoplasma associated diseases until now is based mainly on indirect control measurements against the transmitting insect vectors. Apple proliferation, one of the economically most important pests in European apple cultivation is caused by the apple proliferation (AP) phytoplasma (‘Candidatus Phytoplasma mali’), which is spread by the psyllids Cacopsylla (C.) picta (Foerster, 1848) and C. melanoneura (Foerster, 1848). Current control measures primarily comprise treatments against these AP phytoplasma transmitting vectors. The surveillance of C. picta and C. melanoneura population dynamics, as well as the determination of their infection rate in the field are crucial prerequisites to develop suitable and appropriate strategies to limit further spread of AP phytoplasma. Furthermore, the analysis of the species composition of the genus Cacopsylla present in apple orchards provides important information about the presence of other insect vectors potentially involved in spreading AP or other diseases. During an intensive monitoring program realized in the valleys of Val Venosta and Burggraviato (South Tyrol, Italy), the hotspots of apple proliferation epidemics, over 13,000 Cacopsylla individuals were captured and the occurrence of 16 species of the genus Cacopsylla was confirmed. The presence of C. picta was recorded in more than 50% of the investigated apple orchards and the natural infection rate of this vector was about 21% in a three-year average. Conversely, C. melanoneura was confirmed in more than 90% of the investigated sites but its low infection rate of about 1 % further supports that it plays a rather secondary role in spreading AP phytoplasma in South Tyrol

Surveying Potential Vectors of Apple Proliferation Phytoplasma: Faunistic Analysis and Infection Status of Selected Auchenorrhyncha Species

Apple proliferation (AP) is one of the economically most important diseases in European apple cultivation. The disease is caused by the cell-wall-less bacterium ’ Candidatus Phytoplasma mali’, which is transmitted by Cacopsylla picta (Foerster) and Cacopsylla melanoneura (Foerster) (Hemiptera: Psylloidea). In South Tyrol (Italy), severe outbreaks were documented since the 1990s. Infestation rates of AP do not always correlate with the population densities of the confirmed vectors, implying the presence of other, so far unknown, hemipterian vectors. By elucidating the species community of Auchenorrhyncha (Insecta: Hemiptera) at a regional scale, more than 31,000 specimens were captured in South Tyrolean apple orchards. The occurrence of 95 species was confirmed, whereas fourteen species are new records for this territory. Based on the faunistical data, more than 3600 individuals out of 25 species were analyzed using quantitative PCR to assess the presence of AP phytoplasma. The pathogen was sporadically detected in some individuals of different species, for example in Stictocephala bisonia Kopp and Yonk (Hemiptera: Membracidae). However, the concentration of phytoplasma was much lower than in infected C. picta and C. melanoneura captured in the same region, confirming the role of the latter mentioned psyllids as the main insect vectors of AP- phytoplasma in South Tyrol