Following research carried out by the Department for Environment, Food & Rural Affairs [DEFRA] in partnership with Fera Science, government approval has this week been given for the release of a biological agent to help curb the spread of the invasive Oriental Chestnut Gall Wasp species.
The UK’s chief plant health officer, Nicola Spence, announced that the parasitoid wasp known as Torymus sinensis would be released as a natural control agent to kill off and thereby reduce the presence of its Asian counterpart, which has been harming the health of Britain’s sweet chestnut trees.
The move forms part of a wider government strategy to address emerging pest and disease threats to Britain’s trees, under the Tree Health Resiliency Strategy of 2018.
The Torymus sinensis wasp being used is already present in England in small populations. The Oriental Chestnut Gall Wasp being targeted was first seen in England in 2015 and is known to cause galls on the buds and leaves of sweet chestnut trees, which damages them. High populations of the wasp can therefore weaken sweet chestnut trees to the extent that they become more vulnerable to other pests and plant diseases.
The method of biologically controlling wasp populations in this way has already been successfully deployed across Europe. Yet, UK government approval for the strategy was only given after a thorough scientific review, which included input from the Advisory Committee on Releases to the Environment and consultation with the public.
Fera Science will control the release of the Torymus sinensis and carefully monitor the progress of the strategy over the next decade.
Neil Audsley, senior scientist at Fera Science, believes that the plan will fulfil its goal of improving the health of Britain’s sweet chestnut tree population.
He said: “Following an extensive programme of research and thorough risk assessment, we are now able to release a biological control agent to reduce the population of Oriental Chestnut Gall Wasp. Biological control is the safest and most effective means to manage pests such as Oriental Chestnut Gall Wasp. This strategy has been successfully used in countries across Europe and will directly contribute to improving the health of sweet chestnut trees in England.”
Chief plant officer Spence commented: “Threats to sweet chestnut trees have increased as a result of tree pests and diseases such as Oriental Chestnut Gall Wasp and Sweet Chestnut Blight. The release of this biological control agent represents a huge step towards protecting the health of sweet chestnut trees and will further enhance the resilience of our treescape.”
