Ash dieback began to spread in Europe in the 1990’s, reaching England in 2012.  It is a fungal disease that slowly but surely interrupts a tree’s ability to transport water.   The fungus responsible is Hymenoscyphus fraxineus, which is native to Asia.  The death / loss of mature trees not only reduces carbon dioxide uptake but also represents the loss of habitats for many species of insects and other animals.  The dead trees are also a hazard to people and property. Though many ash trees have now died after infection with this fungus, there is a small glimmer of hope on the horizon.  Some British ash trees are evolving a degree of resistance to the fungus.  Scientists from Kew and Queen Mary University of London have studied the genetic makeup of many mature european ash trees, and also hundreds of young saplings (at Marden Park in Surrey).   This revealed that resistance was more commonly found in young trees - a shift in the genetics of the trees within a generation.   The resistance to the fungus is NOT complete, but if these young trees make it to reproductive maturity then there will another chance for natural selection to ‘refine ‘ the process, through their offspring. However, it may be that a careful breeding program will be needed to establish true resistance / immunity. Interestingly, ash dieback has not reached America but the emerald ash borer has.  This insect is spreading and killing trees.  It is another example of the effects of the globalisation of world trade. Insects and other animals from across the world are being ‘mixed up’, moved from their native regions to new areas where they spread and cause damage as their predators and / or parasites have not travelled with them.   Trees and shrubs are now facing challenges and threats at an unprecedented rate. see also :  https://www.qmul.ac.uk/media/news/2025/science-and-engineering/se/british-ash-woodland-is-evolving-resistance-to-ash-dieback-.html  

JAcross Europe, the red squirrel is recognised as an endangered species.  The U.K populations are at risk due due to :- Habitat loss Competition with Grey Squirrels The effects of the squirrel pox virus The last two are a result of the introduction of the grey squirrel from America in the 19th century. Red squirrels are at home in all types of woodland and may even be seen in parks and gardens, but they 'like' mixed conifer forests best.  Scotland is home to many of the U.K's red squirrels. The number of squirrels is quite small – estimates of their number vary, perhaps there are less than 300,000* across the whole of Britain.   The status of red squirrel populations is a matter of considerable interest. [caption id="attachment_42416" align="alignleft" width="300"] Screenshot[/caption]  In 2014, it was noticed that some members of the Scottish red squirrel populations had abnormal growths on their ears, snout and limbs. Further investigations found that the squirrels were suffering from leprosy.  Leprosy  is a bacterial infection,  caused by two different species of mycobacteria: Mycobacterium leprae and Mycobacterium lepromatosis.   The two types of  bacteria have slightly different distributions in the squirrel populations of the U.K.  Whilst leprosy in squirrels was first reported in 2014,  it is likely that the disease has been around in squirrel populations for much, much longer, probably hundreds of years. Profesor Verena Schünemann,  Christian Urban et al have studied bacterial DNA extracted from human skeletons, dating from 400 CE to 1400 CE with deformities associated with leprosy.   They 'reconstructed' the genetic makeup of mediaeval forms of the bacterium.  Leprosy was not uncommon across Europe in mediaeval times - indeed up to the sixteenth century.   Disease, in its many forms , was a common part of life -  dysentery, diphtheria, typhoid, smallpox, and plague meant that life expectancy was limited. The last indigenous case of leprosy in the UK dates back to 1798.  In humans, leprosy causes muscle and nerve damage, which lead to deformity, blindness and disability.   Interestingly, research by Dr. Sarah Inskip has revealed that a pre-Norman skull [found in Hoxne in Suffolk] had a leprosy strain related to a form known to affect squirrels.  The same strain has also been found in medieval scandinavian skeletons.  It is possible that the  trade in squirrel pelts (and meat) could have contributed to the spread of the disease. Strong trade connections with Denmark and Sweden were in full flow in the medieval period.  Squirrel fur was also used as a lining for fine clothes and squirrels were kept as pets by some. The historical spread of leprosy is not fully understood.  The disease may have passed from squirrels to humans or vice versa in historical times.  Further study of the microbes that cause this disease (and that in squirrels) will help determine how the disease is acquired and transmitted.    The risk to human health is low. (Even so, good hygiene should be followed during any contact with wild animals). Professor Anna Meredith  (University of Edinburgh) is researching into this disease in squirrels.   Further reading / articles: https://www.newscientist.com/article/mg14819991-200-virus-blamed-on-invading-squirrels/ https://www.science.org/doi/10.1126/science.aah3783 https://www.theguardian.com/science/2017/oct/25/medieval-love-of-squirrel-fur-may-have-helped-spread-leprosy-study-reveals https://www.sciencedaily.com/releases/2017/10/171025103109.htm

Should wolves be reintroduced into the landscape. Wolves are regarded as a keystone species in many areas . A keystone species is often a predator that prevents a particular herbivore from ‘eradicating’ a prominent plant species. Without the predators, the herbivore populations can explode, wiping out particular plants, and dramatically altering the character of the landscape / ecosystem.  The logic for the reintroduction of the wolf relates to bringing deer populations under control. Relatively few  wolves can have a significant effect of deer numbers.  Wolves not only kill deer, but keep them on the move restricting their browsing activities. Though the exact red deer population is unknown, estimates for Scotland suggest it is about 400,000.  What is clear is that the deer browsing is having a significant effect on the natural regeneration of woodland and forest throughout the region.  This lack of natural regeneration has contributed to the decline and loss of native woodland.  Indeed, Scotland has a low percentage of woodland cover (approximately 4%).  Natural regeneration does occur  where measures are in place to exclude deer, such as fencing;  Or where deer numbers are below four per square kilometre In these conditions, seedlings can then establish themselves and grow towards maturity. Researchers at the University of Leeds are suggesting that a population of 167 wolves across the Cairngorms, South-west Highlands. Central Highlands and North-west Highlands would be sufficient to reduce the red deer population to a level that would allow natural regeneration to occur.  This natural regeneration would mean more trees, more natural woodland, which in turn would lead to greater carbon sequestration, possibly removing one million tons of carbon from the atmosphere each year.   Their calculations, using a predator prey model for the wolves and deer, suggest each wolf would effectively result in an additional uptake of some 6000+ tonnes of carbon.  It is possible that wolf reintroduction would also lead to: Increased ecotourism A reduction in deer related road traffic accidents / collisions A reduction in Lyme disease (fewer ticks carrying the bacterium Borrelia burgdorferi.  A reduction in the cost associated with deer culls, deer management However, against these potential benefits, there are concerns of public acceptance of wolves in accessible spaces, the challenges they may bring to livestock farmers (especially sheep farmers), and the impact on the deer stalking community.   Whilst wolves were once common in the British landscape, they have not been present (except in wildlife parks) for centuries.  Wolves likely became extinct in England during the reign of Henry VII (1485 - 1509), though wolf bounties were still offered in some parts until the 19th century. In Scotland, at one time (during the reign of James VI of Scotland), wolves were considered such a threat to travellers that special houses / rest places (Spittals) were built along the travel routes for the nighttime protection of travellers.  The Spittal of Glenshee was one such refuge.  At Eddrachillis, the people resorted to burying their dead on an offshore island so that the graves were not disturbed by wolves.   “Thus every grave we dug The hungry wolf uptore And every morning the sod Was strewn with blood and gore Our mother earth had denied us rest On Ederachillis shore” From A book of Highland Minstrelsy (1846) Wolf populations likely peaked in the latter half of the sixteenth century, causing so much damage to cattle in Sutherland that in 1577 James VI ordered wolf hunts three times a year.  According to some accounts, the last wolf to be killed in Scotland was shot in Perthshire in 1680, though there are some claims that a few may have survived into the 18th century. The modelling of the effects of wolf re-introduction by Liverpool University is not the first study suggesting that Scotland’s woodlands and forest would benefit from the return of wolves. However, whether the idea will gain public acceptance or make significant headway remains to be seen.  

Climate change is introducing disease to new areas as it favours the spread of disease vectors, such as mosquitoes.  Usutu is a virus disease that originated in South Africa, it is spread by mosquitos and affects birds, particularly blackbirds and owls.  Whilst birds are the primary hosts to the virus, it can infect ‘incidental hosts’ such as bats and humans, through insect bites. The virus has been found in a number of mosquito species in Africa and Europe.  In the U.K,  and Europe the main vector is Culex pipiens - the common house mosquito or northern house mosquito.  The virus has probably spread through the movement of migratory birds between Africa and Europe, and is now present in many European countries. The virus was first detected in the London area in summer 2020 and was associated with a decline in Blackbird numbers. Blackbird numbers have declined by approximately 40% since 2018. The virus was then detected in Cambridgeshire in 2023.  It seems that most Usutu infections in humans do not cause disease and so the risk to human health is considered ‘low’.  There is no evidence to date that the consuming poultry poses a risk to our health.  However, the detection of Usutu in the UK marks the first time that a mosquito-borne virus capable of passing  from animal hosts to humans has emerged in this country.  Its speed and spread are being monitored as it may model how other mosquito borne disease arrive here. A virus that may be a particular cause for concern is the West Nile virus.  This virus spreads in a similar way to Usutu and needs similar climatic conditions.  West Nile virus, also transmitted through mosquito bite, can cause fever, vomiting and diarrhoea.  At present, there is no vaccine available.  West Nile virus was detected in the Netherlands in 2020, and there is concern that the changing climate could facilitate its spread in Europe.

Native oak trees – keystone species in our woodlands - are under threat from Acute Oak Decline (AOD). The disease is increasingly affecting mature native oak trees across Britain, causing rapid decline and death within as little as 4-5 years. We are seeking help from woodland owners and managers for an important new research project aiming to monitor the health of oak trees across the country. We want to capture the current health of oak trees so we can make comparisons between affected and symptom free woodlands. We hope to understand the differences in environment, underlying health of the trees and importantly the role of management in improving outcomes. AOD can be diagnosed by a depleted oak crown, black stem bleeding, and D-shaped exit holes (left by the Agrilus biguttatus beetle). The disease can seriously diminish health and resilience of infected trees, for example by making them more susceptible to honey fungus. AOD can spread within a woodland once introduced and exacerbate existing stresses. Sylva Foundation is working closely with scientists from Forest Research and Aberystwyth University to understand more about this devastating disease. We are looking for volunteers to assess five or more oak trees, between June and August. Using a purpose-built web app, you will help by assessing each oak tree which should take no more than 5 minutes. The data will then be shared with researchers via Forest Lab. Please sign up to the project today to help this important research. Simply click on Forest Lab after creating an account (free) in myForest here Full details about how to take part and data privacy are provided at sign-up. NOTE : Celyn is a researcher at Aberystwyth University,  working with Forest Research and SYLVA  

Much has been written about the explosion of the UK deer population in recent times, and the damage to woodlands through their browsing activities.  However, the grey squirrelis associated with tree damage.  The grey squirrel is not just the 'cheeky chap' who steals the bird food in the garden, it is a serious pest.    The grey squirrel is a non-native species.  It was introduced in the 19th century.  The squirrels have spread across the country and have displaced the native red squirrel from many areas (either through competition or disease).  The grey squirrel's bark stripping activity now poses a threat to the sustainable management of woodlands. Gnawing of the bark means that they can get to the sweet, sap filled tissue (phloem) just beneath the bark. This tissue is responsible for the movement of sugars and other organic molecules around the plant (known as translocation). If the gnawing extends around the stem then the tree is ‘ringed’ [i.e a complete circle of bark and underlying tissue is removed]  then the tree us likely to die.  The squirrels tend to take bark from the main stem (and branches). The bark stripping may : Lead to the loss of particular tree species (for example, beech) Lead to the loss of insect / spider and fungal species associated with the loss of tree species, i.e. a loss of biodiversity allow fungal infection of the tree Reduce carbon capture Reduce the economic value of timber Act as a disincentive to creating new woodland for timber In order to reduce squirrel damage, it is important to Start inspecting for damage in late February as damage typically occurs in early Spring.  Examine the base of trees for damage. Look for ‘tester patches’ made by squirrels (to which they may well return later). Check young, broadleaf trees as they are particularly favoured by the squirrels.  Oak and beech are quite vulnerable to damage (see image of damaged beech trunk below). Recent research* at Bangor University has investigated the microbiome of the squirrel in relation to its bark stripping activity.  The microbiome of the gut refers to the various micro-organisms found with the intestines.  Analysis of bacterial DNA found in the colon of great (and red) squirrels revealed that grey squirrels had 'oxalobacter' bacteria in their colons.  These bacteria are able to 'release / access' calcium from the tree bark to the squirrels.  Calcium is an important nutrient in terms of bone building and is also involved in muscle contraction. had  a more diverse bacterial population in the colon. These findings may help explain why the grey squirrel 'outcompetes' the red squirrel.  Their more diverse gut microbiome may mean that they can access a greater range of resources. For example, grey squirrels can digest acorns, which red squirrels cannot;  this is possibly associated with tannin content of acorns. In order to reduce damage in a woodland, the number of grey squirrels may need to be managed.  This can be done though trapping or shooting.  Trapping is a legally acceptable and effective way of controlling grey squirrels in most situations. Grey squirrels can be trapped throughout the year though March to September is a good time as food is less abundant. Through autumn, berries, nuts and seeds [natural foods] are available so trapping is less successful.  Details of the various types of traps and their use / placement may be found at: https://greysquirrelcontrol.co.uk/trapping-method.php https://www.britishredsquirrel.org/wp-content/uploads/2016/07/Grey-Squirrel-Best-Practice.pdf https://basc.org.uk/pest-and-predator-control/grey-squirrel-control-with-live-capture-traps/ https://www.britishredsquirrel.org/wp-content/uploads/2016/09/Trapping-Protocol.pdf  https://bpca.org.uk/a-z-of-pest-advice/squirrel-control-how-to-get-rid-of-squirrels-bpca-a-z-of-pests-/188983 To go down the ‘shoot to kill’ route then there are a number of rules and regulations to observe.  Details may be found in the link below : http://www.britishredsquirrel.org/grey-squirrels/grey-control/ It is hoped that eventually a form of oral contraception will be developed, which will offer a non-lethal and humane means of population control. Full details of this research work may be found here

Solar farms have sprung up across the country with hundreds or thousands of solar panels, linked together in fields.  Now, researchers in the States have shown that sowing grasses and wild flowers in-between the panels on solar farms resulted in: A significant increase in the number of beneficial insects (bees in particular benefitted) An increase in insect diversity beneficial 'spillover effects' on adjacent farmland. The solar farms under study were sown with specially designed seed mixes. See also the previous woodlands  blog on solar panels and wildlife The seeding of solar farms would seem to offer support to : Renewable Energy Generation: Biodiversity Pollination services Habitat restoration: in fields that may have been damaged by intensive agriculture and / or development. They can also act as a refuge for native plants and wildlife. Erosion control: the root systems of native plant species (which penetrate to different depths) help prevent soil erosion. Reduced maintenance costs: as less mowing / weed control needed. The cabbage white butterfly is generally regarded as the enemy by the keen vegetable gardener.  If you are growing brassicas - cabbages, cauliflowers, brussels sprouts, broccoli, kale or pak choi, it is likely that you will have these butterflies as summer visitors.  The butterfly is white with black spots on the wings.  Males have a single spot on each of the forewings, whereas the females have paired spots. The butterflies are attracted to the plants as they produce the chemical - glucobrassicin. The butterflies can sense the glucobrassicin through the hairs on their front legs (they have three pairs of legs, a pair on each segment of the thorax). This chemical, glucobrassin, stimulates them to lay their eggs on the leaves of cabbage and other brassicas.  A female can lay up to 800 yellow eggs. These eggs may hatch and the green / black caterpillars emerge.  These caterpillars can double their mass in a day through their voracious feeding.  The adults are attracted to the glucobrassicin in the brassicas just as the caterpillars ‘enjoy’ the chemical - SINIGRIN.   When leaf tissue is damaged, the sinigrin is broken down into a mustard oil, responsible for the pungent taste of Cruciferous vegetables. There are a number of strategies that may help keep the butterfliess away from your crops, and reduce the damage by the caterpillars. Cover the plants with an insect proof mesh Offer ‘sacrificial brassicas’ away from the main crop Use companion / mixed planting, so that beneficial insects have 'hiding places' and it is more difficult for the female cabbage whites to find the brassicas.  Also, by mixing up the planting with herbs and other veg, it makes it a bit more difficult for the caterpillars to move from cabbage to cabbage etc. If you do need to use an insecticide, consider using the products derived from Bacillus thuringiensis.

The woodlands blog has previously reported on the damage being wreaked by bark beetles.  These beetles may be small (less than a centimetre in length) but their effects on the western forests of North America has been immense. Some areas have lost 90% of their conifers.   Outbreaks of these beetles have been increasing in size and severity.  Indeed, across Europe, the eurasian bark beetle (Its typographus) has killed millions of conifers. Whilst bark is broadly protective, it can also offer a home to certain insects.  Bark beetles lay their eggs just below the bark so that when the larvae hatch, they can feed on the nutrient-rich living tissue of the cambium and phloem. Consequently, the tree's transport systems begin to fail.  The beetles may also introduce disease-causing fungi and bacteria. Ageing stands of trees coupled with warmer winters, which help the overwintering stage of the insect, have contributed to the spread of bark beetles. .  Conifers, by their nature, are not defenceless.  When a pine tree is cut / wounded, it produces a pale yellow and sticky fluid - RESIN to seal the cut or wound [see above image]. This material helps prevent the entry of pests or pathogens, and can stem water loss. The resin may trap insect invaders as  witnessed by those trapped in time capsules of amber.  Resin is rich in terpenes, these are used in the building of many complex organic molecules and contribute to the make-up of the volatile oils, produced by many plants.  Terpenes are made from units of isoprene, which has the formula C5H8. So the basic formula of a terpene is (C5H8)n, where n is the number of isoprene units that have been joined together.  Terpenes are also readily available in coniferous oils, which contribute to the unique smell of a pine forest or a burning log. [caption id="attachment_40973" align="alignleft" width="300"] Old and dying tree[/caption] These ‘chemical defences’ should trap, poison or deter an insect invader, such as the bark beetle.  But it would seem that bark beetles ‘don’t mind’ these defences. Research suggests that the eurasian bark beetle might have an ally.  Certain fungi (from the genus - Grosmannia) are found in association with these beetles. When the  Grosmannia fungi infect spruce trees they alter the chemical profile the trees, so that infected trees produce different volatile chemicals - ie they smell different.  The bark beetles are able to detect these differences and exploit this ‘breach’ of the trees natural defences.  The unique chemical profile of infected trees and the pheromones produced by the beetles probably help explain the swarming behaviour of the bark beetles.  A heavy beetle infestation results in the death of a tree. However, there is a possible positive in this rather sad tale.  At present, traps for bark beetles rely solely on using pheromones but if the pheromones can be combined with the chemicals produced by the fungi then it opens the door to more effective beetle traps.