Elena Costi

Indigenous arthropod natural enemies of the invasive brown marmorated stink bug in North America and Europe

Since the establishment of the brown marmorated stink bug, Halyomorpha halys (Stål) (Hemiptera: Pentatomidae) in North America and Europe, there has been a large, multi-group effort to characterize the composition and impact of the indigenous community of arthropod natural enemies attacking this invasive pest. In this review, we combine 98 indigenous natural enemy datasets spanning a variety of sampling methods, habitats, and geographic areas. To date, the vast majority of H. halys biological control research has focused on the egg stage, using sentinel egg masses to characterize indigenous parasitoid and predator communities and their contribution to H. halys egg mortality. Although egg parasitism and predation levels by indigenous natural enemies are low (typically <10% each) in most surveys, total egg mortality attributable to natural enemies can be higher (typically between 5 and 25%; up to 83%)—even though these values were likely underestimated in most cases because some mortality due to biological control was not recognized. In North America, where the most data are available, it appears that the relative prevalence of different indigenous parasitoid species varies among habitat types, particularly between crop and non-crop habitats. Predator species responsible for egg mortality are much less commonly identified, but appear to include a wide variety of generalist chewing and sucking predators. To date, studies of natural enemies attacking H. halys nymphs and adults are relatively rare. Based on our review, we identify a number of key research gaps and suggest several directions for future research.

SEARCHING FOR NATIVE EGG-PARASITOIDS OF THE INVASIVE ALIEN SPECIES HALYOMORPHA HALYS STÅL (HETEROPTERA PENTATOMIDAE) IN SOUTHERN EUROPE

Halyomorpha halys is an invasive species, originating from East Asia, which was accidentally introduced in some areas of North America and Europe, where severe damages to different vegetable crops and fruit plants were recorded. Several studies in different countries focused on the possibility to apply biological control by means of egg- parasitoids. The main egg-parasitoids in the original area are unfortunately non-specific and thus the application of classical biological control is questionable. On the other hand, the possibility of using augmentative biological control by native egg-parasitoids able to exploit the new host is an interesting possibility in both Europe and the USA. In a preliminary assay, frozen egg masses of H. halys were exposed in the field in Central Italy. Results showed that some eggs were exploited by parasitoids belonging to the species Anastatus bifasciatus and Ooencyrtus telenomicida . Therefore, different native egg-parasitoids species widespread in Europe were tested in the laboratory in order to explore their ability to parasitize H. halys eggs. To this end, no-choice tests were carried out in climatic chambers (26°C, 70%RH, 16:8 L:D) in order to evaluate the parasitization potential of females collected in the wild. Conducted tests pointed out that A. bifasciatus and especially O. telenomicida may be potential candidates for the biological control of H. halys . In particular, O. telenomicida was able to parasitize the 35.56% of the exposed host eggs in the lab tests. New adults successfully emerged from the 22.92% of the eggs, and on the whole, this egg-parasitoid caused a significant hatching reduction of the H. halys eggs (more than 70%). Conversely, Telenomus chloropus and Ooencyrtus pityocampae were less promising species as biocontrol agents of this agricultural pest. Preliminary trials in pear orchards consisting of field releases of laboratory-reared specimens of O. telenomicida, one of the potential candidates for biological control, showed that this parasitoid is actually able to discover egg masses of H. halys (sentinel frozen egg masses) and to successfully parasitize them.

Monitoring of the invasive Halyomorpha halys , a new key pest of fruit orchards in northern Italy

Halyomorpha halys is an invasive polyphagous pest with a high negative impact on fruit orchards and other agricultural crops in the USA. In Italy, it was first detected in 2012 in Emilia Romagna, a northern region that is among the major European tree fruit production areas. A specific monitoring programme using active techniques was carried out in pear orchards and adjacent uncultivated areas between 2014 and 2016 to assess the abundance, seasonality and impact of H. halys and other phytophagous Heteroptera in the field. It emerged that just a few years after first discovery, this invasive species already largely outnumbers all the other Heteroptera and that it is a season-long pest for pear crops. Severe yield losses are reported in different farms, especially on the orchard borders, with more than 50% deformed fruits. Mirids are mostly found in the grassy areas and crops, and the other phytophagous Heteroptera, only occasionally detected in the orchard trees, occur mainly on hedges and other crops. Our survey demonstrates for the first time the great damaging potential of H. halys as a new key pest of orchards in southern Europe. The study also identified the patterns of seasonal abundance of adults and nymphs in the orchards and their uncultivated surroundings, providing baseline data for the development of specific strategies for sustainable management.