Tree Diseases and Pests
Bleeding canker is a disease that affects horse chestnut trees, it was first reported in Britain in the 1970’s. It was recognised in the USA much earlier in the 1900’s. Symptoms of the disease were associated with 2 types of pathogens. Today, diseases around the UK spread much more dramatically than previous years. In 2000, only 4 cases were reported but this rose to nearly half of the horse chestnut trees in 2007 in Britain showed some degree of symptoms.
The larvae of the Oak Processionary Moth can affect the oak tree and humans and animals. This can then lead to implications with health . The moths were active in oak trees in and around the affected areas in London, Surrey, West Berkshire and Hertfordshire in the spring and summer of 2016. The disease was carefully controlled with treatment for affected trees with approved insecticide to kill the Oak Processionary moths while they were still young enough for the treatment to be effective. The situation was controlled not long after the outbreak and therefore stopped the spread of disease.
The EAB is an exotic beetle. It is a member of the beetle family, the beetle causes significant damage to ash trees to not only the trees health but it’s appearance too. Ash trees have been widely planted in urban situations there, and are economically important as a commercial timber crop. The death of many ash trees, within two to three years of first showing signs of ill health, is causing considerable concern. A resolution could be to possibly plant more trees.
AOD is a new disease mainly affecting native oak trees in Britain and considered to have first made a presence in Britain 30‑35 years ago. Affected trees tend to have vertical, weeping fissures that seep black fluid down the trunk. In the live tissue beneath the bleeds a lesion is created. This is a sign of tissue decay. Some trees die 4-6 years after onset of symptoms. Forest Research is involved in studies to investigate the relationship in more detail.
The beetle poses a serious threat to a range of broad-leaved trees. It has caused major damage to trees in the USA and Italy since being accidentally introduced to those areas in recent years, and there have been outbreaks in several other EU countries. The beetles stay close to the site of original infestation in the early stages of an outbreak. However, they can fly more than 2 km. After checking climate data it suggests that most of England and Wales and some warmer coastal areas of Scotland are suitable for beetle establishment, but south-east England and the south coast have a much greater risk. The life-cycle from egg to beetle is one to two years in parts of Asia, and can be as long as four years in the UK. The beetles emerge during the summer and will mate and lay eggs, they die shortly after.
The horse chestnut leaf miner is a combination of an exotic pest and a killer disease. This could threaten to wipe out the UK’s conkers and horse chestnut trees within 15 years. The moth first came to the UK in 2002. They affect Britain’s population of horse chestnut trees along with the bleeding canker disease. The trees now barely last 5 years. The moth’s larvae effectively eat the trees’ leaves from the inside out by mining them. This destroys the leaf tissues, causing them to turn pale or brown. This has an impact on the trees’ ability to photosynthesise and their overall health. It also has an impact on the size of the conkers that are grown on the trees, which are smaller than usual.
When you notice one or two withered, blackened ash leaves in the hedge in you shouldn’t ignore it. Don’t leave it for month or two it will then be impossible to ignore what’s going on and a result of this may be that you can’t cure the disease. The signs of Hymenoscyphus fraxineus, are clear to see. Blackened leaves then droop from just about every other branch. The smooth, grey bark is stained and marked.
Plane trees in Britain are suffering from Massaria disease. This disease can cause large lesions on the upper surfaces of major branches and can cause the branch to drop. In 2009 tree management teams in London started to notice large lesions and branch drop on the branches of plane trees. However it is not yet clear whether a fungus is the primary cause of the disease, researchers are still having a look into the disease to try and find the main cause. The result of this is that the main cause is still unknown and will take a lot of work
The wasp was first seen in the UK in 2015, a second site was later confirmed in a single street in Hertfordshire, England. The oriental wasp is an insect of Asian origin which affects sweet chestnut trees. The wasp is a pest of sweet chestnut trees due to the activity by its larvae which then causes galls to form on the buds, leaves and leaf stalks. The galls start out green when they begin to develop about March, they then turn red by June. They start to dry out and turn brown over the summer, when the adult wasps emerge from them, they can cause the leaves to drop early.
The impact of the pathogen is currently limited in the UK as a whole. However, it is potentially serious for the Upper Teesdale juniper. This is because these are rare plants and this site has the second largest population of the species in the UK. Common juniper is already known as important and vulnerable, because since about 1990 its extent and condition have declined considerably. Juniper is also a key food plant for a wide range of invertebrates and birds, which means it has a unique and specialised group of associated insects, fungi and lichens. The establishment of P. austrocedri in the UK could further contribute to its decline.
SCB is a plant disease caused by a fungus, this pathogen has caused severe epidemics resulting in death and dieback of Sweet Chestnut trees. This devastated sweet chestnut forests in the USA during the first half of the 1900’s, killing an estimated 3.5 billion trees. Although losses have not been on the same scale in Europe and tree losses have been regionally significant. Sweet chestnuts are grown commercially in Europe for the timber and nut markets and therefore this impacts the economy
Dothistroma Needle Blight is also known as RBNB because of the colourful symptoms it shows on pine. The pest causes premature needle defoliation this means a loss of yield and in severe cases; tree death. Up until the 1990’s, the disease was primarily a concern in the Southern Hemisphere but now it is a concern all over the world. Since the late 1990’s, this pest has been found in many forests which grow susceptible pine species that are unfortunately all being affected.
P. ramorum is a fungus-like pathogen which causes extensive damage to a range of trees and plants. The disease is known in the USA as ‘sudden oak death’ where as in the UK its known as ‘Larch tree disease’ and ‘Japanese larch disease’. However, the strains of the pathogen found in Britain have had little effect on British native oak species. The first UK finding was made in 2002 at a garden centre in Sussex, whereas the first record of P. ramorum on a mature tree in the UK was on a 100-year-old southern red oak in 2003.