Agrilus Biguttatus Research Articles

A checklist of the Ukrainian Xoridinae (Hymenoptera, Ichneumonidae).

The Ukrainian Xoridinae list containing 28 species is reviewed. Four species, Xorides flavotibialis Hilszczanski, 2000, X. hedwigi Clement, 1938, Xorides rufipes (Gravenhorst, 1829), and X. rusticus (Desvignes, 1856) are recorded in the Ukrainian fauna for the first time. Agrilus biguttatus F. is recorded as a host of Ischnoceros caligatus (Gravenhorst, 1829) for the first time.

Analysis of Unmanned Aerial System-Based CIR Images in Forestry—A New Perspective to Monitor Pest Infestation Levels

The detection of pest infestation is an important aspect of forest management. In the case of the oak splendour beetle (Agrilus biguttatus) infestation, the affected oaks (Quercus sp.) show high levels of defoliation and altered canopy reflection signature. These critical features can be identified in high-resolution colour infrared (CIR) images of the tree crown and branches level captured by Unmanned Aerial Systems (UAS). In this study, we used a small UAS equipped with a compact digital camera which has been calibrated and modified to record not only the visual but also the near infrared reflection (NIR) of possibly infested oaks. The flight campaigns were realized in August 2013, covering two study sites which are located in a rural area in western Germany. Both locations represent small-scale, privately managed commercial forests in which oaks are economically valuable species. Our workflow includes the CIR/NIR image acquisition, mosaicking, georeferencing and pixel-based image enhancement followed by object-based image classification techniques. A modified Normalized Difference Vegetation Index (NDVImod) derived classification was used to distinguish between five vegetation health classes, i.e., infested, healthy or dead branches, other vegetation and canopy gaps. We achieved an overall Kappa Index of Agreement (KIA) of 0.81 and 0.77 for each study site, respectively. This approach offers a low-cost alternative to private forest owners who pursue a sustainable management strategy.

A review of Agrilus biguttatus in UK forests and its relationship with acute oak decline

Agrilus biguttatus Fab. (Coleoptera: Buprestidae) is a European bark-boring beetle whose larvae feed in the vascular tissue of oak trees. Until recently, it was considered rare in Britain, but sightings have become more frequent and it is often found on weakened trees suffering from Acute Oak Decline (AOD). This rapidly acting syndrome is characterized by patches of dark sticky fluid exuding from cracks on the trunk, with areas of necrotic tissue beneath, probably caused by a pathogenic bacterial component. However, the frequent association of AOD with the larval galleries and distinctive adult exit holes of A. biguttatus has raised concerns that the beetle may be contributing to the AOD syndrome or hastening the mortality of affected trees. This review evaluates the potential role of A. biguttatus in the AOD complex. Information on the beetle's life cycle and ecology is assessed along with the apparent increase in its abundance and distribution in the UK, and likely mechanisms of host selection. Oak tree defences against the beetle are discussed, as well as risk factors influencing susceptibility. Research on related Agrilus species is reviewed so that insights into the relationship between the beetle, the bacteria and the host tree can be made through comparisons with more extensively studied species. Possible management options in an AOD context are considered, and priority areas for future research are identified.

A description of the symptoms of Acute Oak Decline in Britain and a comparative review on causes of similar disorders on oak in Europe

Acute Oak Decline (AOD) is a relatively new decline-disease affecting both native oak species (Quercus robur and Q. petraea) in Britain. The key aim of this study was to describe the symptoms, and signs of AOD, to set a baseline. The second aim was to compare and review the European literature on what appear to be similar disorders on oak. AOD is characterized by four key features: weeping patches more-or-less vertically aligned on oak tree trunks; cracks between bark plates from which dark fluid seeps; inner bark necrosis and the presence (in >90 per cent of cases) of larval galleries of the oak buprestid, Agrilus biguttatus, on the phloem–sapwood interface. In this study, it was noted that although larval galleries were present in the inner bark in 19 of 21 trees, the ‘D-shaped’ exit holes of the adult beetles were seen less frequently on bark plates of affected trees (33 per cent of cases). Similar disorders reported in Europe are compared with AOD in Britain and potential causes of the condition discussed. Based on the unmistakable symptoms, it is hypothesized that AOD is a distinctive, identifiable condition within the broader oak decline syndrome.

Field observations of visual attraction of three European oak buprestid beetles toward conspecific and heterospecific models

Agrilus biguttatus Fabricius, Agrilus sulcicollis Lacordaire, and Agrilus angustulus Illiger (Coleoptera: Buprestidae) are three beetle species associated with oak trees [Quercus spp. (Fagaceae)] in Europe. In Hungary, all three species were observed in the foliage near freshly cut oak log piles. Agrilus biguttatus was active later in the afternoon, whereas the other species were observed earlier in the day. Dead female models of these three native Agrilus species, as well as the native species Agrilus cyanescens Ratzeburg and the non-native Agrilus planipennis Fairmaire, were pinned onto adjacent leaves in direct sunlight to observe the visual mating approaches of the local male populations. Agrilus biguttatus and A. sulcicollis males flew toward and landed directly on the models from a distance of 1 m. Agrilus angustulus flew toward the models from a similar distance, but rather than landing directly on a model would alight on the leaf, 1-2 cm away, before walking closer to the model while antennating it. For all three species, there was substantial cross-attraction to models of other species. Both A. biguttatus and A. sulcicollis males chose A. angustulus models less often than their respective conspecific models. Likewise, A. angustulus males approached A. sulcicollis models less often than their normal conspecific models. Agrilus biguttatus males attempted to copulate with both A. biguttatus and A. planipennis models, afterward remaining with them for several minutes. Agrilus biguttatus males spent more time on A. planipennis models than on conspecific models. Thus, there is substantial cross-species attraction in visually mediated mating approaches and copulation behavior. These findings suggest a common behavioral template for visual mate-finding among buprestids and a large degree of close-range mating compatibility between A. biguttatus and A. planipennis.