No abstract

1 The two spotted oak buprestid, Agrilus biguttatus Fabricus, is implicated in oak decline events across Europe, and is strongly linked to Acute Oak Decline in the U.K., although its role in the syndrome remains under investigation. In the U.K., the beetle is restricted to south and central England. The present study aimed to improve our understanding of the beetle's life history and thermal requirements, intending to explain its U.K. distribution, and to collect data for lifecycle modelling. 2 Novel methods were developed to collect and culture the beetle in the laboratory, which enabled experiments to be carried out, providing data on the beetle's sex ratio, longevity and fecundity, and the development rates of eggs, larvae and pupae at constant temperatures. 3 On average, females lived for 63 days and laid 82 eggs. Larvae developed through four instars. Sex ratio varied by site, with no overall trend apparent. 4 The development rates of eggs, larvae and pupae (to adult emergence) had linear relationships with temperature, with lower developmental thresholds of 12.1, 11.9 and 15.1 ∘ C, respectively. For each life stage, degree-day values were calculated. Beetles appeared to have an obligatory prepupal diapause at all temperatures studied, up to and including 25 ∘ C. 5 The implications of the developmental findings for the beetle's current distribution, as well as the possible effects of climate change, are discussed. The beetle appears to be thermally limited in the U.K. and, if so, its distribution, and perhaps that of Acute Oak Decline, may alter under climate change.

Scots pine (Pinus sylvestris) is frequently planted as a monoculture, but it is also grown in mixed plantations with other native trees such as pedunculate oak (Quercus robur). Both pine and oak form ectomycorrhizas that cover their roots and extend into the soil, facilitating tree water and nutrient uptake in exchange for photosynthetic carbon. Forming the interface between the soil and tree roots, mycorrhizal fungi are key drivers of biogeochemical cycling in terrestrial ecosystems and play an important role in the successful establishment of tree seedlings. They can, however, be susceptible to changes in the soil environment and in their hosts. Both environment and neighboring hosts affect how fungi colonize roots and may affect their host preference. Despite the importance of mycorrhizal fungi in forest ecosystems, little is known about the biodiversity and functional effects of mycorrhizal communities in mixed compared with monoculture plantations. Changes in mycorrhizal richness and composition can result in changes in functional groups with consequences for forest ecosystem stability and functioning. We compared pine mycorrhizas in eight mixed plantations of pine and oak and eight pine monocultures in two forests in England, and we investigated the main factors driving their taxonomic and functional composition. Geographical location and litter pH explained over 50% of the variation in pine mycorrhizal communities. Different environmental factors affected taxonomic and functional composition across stands, indicating functional redundancy. Pine tended to associate with more fungi in the presence of oak, but the abiotic environment exerted a stronger influence than oak presence on pine mycorrhizal diversity

BACKGROUND Agrilus bigutattus (Fabricius) is a forest pest of increasing importance in the United Kingdom. The larvae damage weakened native oaks and are thought to contribute to premature tree death. Suspected links with acute oak decline (AOD) are not yet confirmed, but AOD‐predisposed trees appear to become more susceptible to A. biguttatus attack. Thus, management may be necessary for control of this insect. To explore the possibility of monitoring beetle populations by baited traps, the host tree volatiles regulating A. biguttatus–oak interactions were studied.RESULTSBiologically active volatile organic compounds in dynamic headspace extracts of oak foliage and bark were identified initially by coupled gas chromatography–electroantennography (GC‐EAG) and GC–mass spectrometry (GC‐MS), and the structures were confirmed by GC coinjection with authentic compounds. Of two synthetic blends of these compounds comprising the active leaf volatiles, the simpler one containing three components evoked strongly positive behavioural responses in four‐arm olfactometer tests with virgin females and males, although fresh leaf material was more efficient than the blend. The other blend, comprising a five‐component mixture made up of bark volatiles, proved to be as behaviourally active for gravid females as bark tissue.CONCLUSIONSThese initial results on A. biguttatus chemical ecology reveal aspects of the role of attractive tree volatiles in the host‐finding of beetles and underpin the development of semiochemically based surveillance strategies for this forest insect. © 2015 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.