Bacteria: Advancement of Control and Knowledge to Save Threatened Oak and Protect them for Future Generations

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Oak trees are iconic in Britain and important to our natural world and economy. Unfortunately, they are under threat from an emerging disease Acute Oak Decline (AOD). Affected trees have weeping stem patches caused by bacteria rotting inner tissues that carry food and water vital for tree life, and larval feeding galleries the oak jewel beetle (Agrilus biguttatus). Disease disrupts the flow of food and water in the tree often leading to its death. Solutions to manage and protect trees are vital to ensure the future of British oak. The role the beetle plays in AOD remains unanswered, but it is thought to be involved in disease process and transmission. If so, at what stage of its lifecycle? How does the beetle find suitable trees to feed and lay eggs on? Do the rot-causing bacteria attract the beetles? We will test these questions using controlled experiments. Trees produce various odours, and plant-feeding beetles such as A. biguttatus use their sense of smell to find suitable trees and mates for feeding and reproduction. By capturing gases given off by the tree, presenting them to beetles and monitoring their response we can find out which ones attract beetles. This interaction can be exploited to protect trees by using attractive odours to pull beetles into traps. Agrilus species can only colonise weakened trees and previous research shows that specific environmental stresses make oak more susceptible to AOD. Main stresses are drought and imbalanced soil nutrition, specifically nitrogen and phosphorous deficiencies. These effects on tree metabolism and function as well as on natural soil and tree microflora will be tested under controlled conditions. This will provide important information about possible microbial additives that could accompany soil nutrition amendments to hasten tree recovery. Until these questions are answered, control of the beetle cannot be implemented and soil amendments and suitable management practices to make trees more robust to attack cannot be introduced.Research will provide a better understanding of who has an interest and stake in oak health. The values, attitudes and actions of people, professionals and policy makers will be examined to help understand reactions and responses to control of the disease and how to work together to develop and implement appropriate management and control. We will collaborate with stakeholders and scientists, build on existing experience, identify values, attitudes and actions and explore knowledge and awareness associated with oaks in urban and rural environments that will be used to promote and facilitate engagement in collective action to protect oak trees.Finally, we will address the question of whether the bacteria present in AOD bleeds on oak are also found in disease symptoms on other broadleaf trees, and if so, are there similarities to AOD that would help understand the infection and rotting processes in AOD. Furthermore, as bacterial tree diseases are generally under-regarded and there is a lack of information available concerning them, the risks to tree host species are unknown as are the implications for control of bacterial spread. Records from Forest Research's Tree Health Diagnostic and Advisory Service (THDAS) show that in the past 5 years over 550 cases of stem bleeding have been reported, 40% of these were on oak but approximately 10% had undiagnosed disease cause. Through laboratory microbial culturing processes from a range of broadleaved trees with stem bleeding symptoms we will isolate, identify and test bacteria for their disease-causing ability. Information about bacteria on these trees would be helpful to manage AOD and also to assess the risks of bacteria to other important native forest tree species that might be susceptible to AOD and other bacterial species. This interdisciplinary project will provide new evidence that can feed into a better understanding of appropriate and acceptable management practices for oak health and resilience.