Assessing invasive bark beetle threats to the UK
Bark beetles (Scolytinae) are amongst the most economically important insect pests in the northern temperate forests. Within the group are numerous species that have the capacity to kill mature trees through direct mass attack or by vectoring pathogenic fungi. Under the projected future climate of increased drought and severe weather events, forests are expected to become more susceptible to bark beetle attacks, and outbreaks are likely to become more widespread. Due to their small size, bark beetles are readily transported in timber products and wood packaging material, and pose a key biosecurity threat worldwide. Potentially damaging species are regularly intercepted entering the UK, but until recently, no surveys have been carried out to investigate whether any exotic species have already established in our forests. This talk will examine some of the threats faced from exotic scolytines, and present some initial results and implications from the monitoring studies now being undertaken.
Asian longhorn beetle Anoplophora glabripennis in southern England: the 2012 outbreak.
Nigel Straw, Nick Fielding, Christine Tilbury & David Williams
Asian longhorn beetle Anoplophora glabripennis is a highly damaging pest of deciduous broadleaved trees. Its larvae bore within the wood of healthy and stressed trees and repeated attacks cause dieback and a general deterioration of stems and branches that leads eventually to the death of the tree. It is native to China and Korea, but has been transported around the world in untreated wood packaging material, and introduced populations have become established in North America and at several locations in Europe. In 2012, the first outbreak of A. glabripennis in the UK was discovered at Paddock Wood in Kent, in south-east England. Surveys showed that the population was confined to a relatively small area and over the next four months an eradication programme was carried out, which involved felling and destroying 2229 trees across an area of 11.5 ha. A total of 66 trees were found to have been attacked by A. glabripennis, mainly sycamores Acer pseudoplatanus, but also small numbers of other Acer species and Populus, Salix, Betula and Aesculus.
Stems and branches that contained A. glabripennis life-stages, or other signs of infestation, were recovered from the outbreak site as the trees were felled, and this material has been analysed to provide information on the history of the outbreak and the life-cycle and biology of the beetle in this part of southern England. Dating the exit holes that were produced by the adult beetles as they emerged, indicates that A. glabripennis had been present at Paddock Wood for about 10 years before it was discovered and that it had been spreading relatively slowly. The majority of A. glabripennis at Paddock Wood also appear to have been taking 3 years to complete their life-cycle, which is longer than the usual 1- or 2-years required by the beetle in its native range or in the USA and southern Europe. It appears therefore, that although A. glabripennis was able to establish at Paddock Wood and was beginning to kill trees, it was close to its climatic limits and its population was not managing to increase or spread very rapidly.
The use of pheromone traps for the early detection and monitoring of oak processionary moth (Thaumetopoea processionea L.)
D.T. Williams, T. Cull, N. Straw and G. Jonusas
Pheromone traps have been used in Europe and the UK to monitor oak processionary moth (OPM) populations, however their efficiency appears to vary depending on a variety of factors, including trap design, the effectiveness of the pheromone lure and the positioning of the trap in the tree canopy. This variation in trap use and efficiency makes it difficult to compare results from different studies, and has hampered efforts in the UK to develop a standard methodology for using pheromone traps to track the current outbreak. The use of a network of pheromone traps should facilitate improved detection of OPM and should allow the earlier discovery of spread from known infested areas into or beyond existing buffer zones around outbreak areas.
In an attempt to improve the methodology of OPM pheromone trapping, experimental trials were conducted within the west London outbreak area in 2011-2014 to evaluate key parameters that are considered influential in determining the numbers of adult male OPM caught in pheromone traps. The results obtained from these trials have enabled the development of a standardized pheromone trapping monitoring system for OPM to be established, which is now being integrated into the wider OPM control programme.
The development of a standardised pheromone trapping protocol is also being utilised in three areas of current research: (1) to investigate the long-term population dynamics of OPM in the UK, primarily in relation to climate variables, but also to consider the effectiveness of management and control strategies; (2) to examine the relationship between pheromone trap catches and the density of larval nests in the vicinity of traps, with the aim of identifying a threshold trap catch so that survey teams might be deployed in a more targeted, timely and cost effective manner; and (3) to investigate how characteristics of the host plant influence pheromone trap efficiency.