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A record number of tree pests and diseases have been reported in the last year, according to a TreeAlert system operated by Forest Research. TreeAlert reports record number of tree pest and disease enquiries

A record number of tree pests and diseases have been reported in the last year, according to a TreeAlert system operated by Forest Research.

The service received its highest number of enquiries since it was relaunched in 2014. The service is crucial in the early identification of new pests and diseases – and is used to help enable their control and track the spread of emerging problems.

Members of the public and conversation groups are encouraged to report pest and diseases to TreeAlert. The increase in enquiries is thought to be partly down to more people visiting the countryside during the pandemic.

Tree health enquiries in the 12 months to 31 March concerned a wide range of species and mostly broadleaf trees. The most common tree species was oak, followed by ash and sweet chestnut.

Highly destructive

Ash dieback was the most commonly reported disease in 2020, and it is now present in most parts of the UK. A highly destructive fungal disease, it is predicted to kill 70-90% of the country’s 100m native ash trees over the next 20 years.

Oak processionally moth (OPM) enquiries made up almost half of all pest enquiries in 2020. Processionally moth caterpillars are pests of the oak tree and are hazardous to human and animal health.

Native to southern Europe and first detected in the UK in 2005, OPM is subject to a government-led programme of survey and control to minimise its spread and impact although sometimes the caterpillars are confused with other species.

Chestnut blight was diagnosed in a number of cases in 2020. This is a serious fungal disease of sweet chestnut trees. Since 2011 the disease has been found on a restricted number of sites in the UK, principally in central and southern England.

The government is taking action to suppress and eradicate the disease including surveillance and destruction of infected trees, and prohibiting the movement of susceptible planting material and wood products.

Forest Research said it was investigating ways of combating the problem by using biocontrol methods based on naturally occurring viruses which infect the causal fungus and reduce its ability to cause disease.

Pest control

Other pests and diseases to look out for include bark beetles which are pests of coniferous trees. Some species can cause significant damage to spruce in the UK and the government is taking action in a bid to control the pest. A newly introduced pest is elm zig zag sawfly. First detected in the UK in 2017, its larvae feed on elm leaves and can severely defoliate trees, damaging their health and associated biodiversity. Acute oak decline is a disease of oak which has emerged since the 1980s and can kill mature oak trees within five years. Forest Research said it was pioneering research to understand the disease and protect oak trees for future generations.

Forest Research identifies tree pests and diseases and provides ad- vice on their management to both en- quirers and government. The service is funded by Defra, the Forestry Commission and the Scottish and Welsh governments.