A new technique to control invasive tree pests such as oak processionary moth (OPM) is proving effective in trials and could be commercially available by next year, the Arboricultural Association Amenity Conference (14-17 September) has heard.
Derived from a naturally occurring insecticide, emamectin benzoate (EMB), and its means of deployment, known as tree micro-injection, it is currently being assessed by the Chemicals Regulation Directorate.
Syngenta turf and landscape manager Rod Burke said: "Tree injection with Revive (which contains EMB) is in use in France and Spain. We are trialling it and hope to gain UK approval next year for the control of OPM, with treatment for horse chestnut leaf miner approved the year after.
"We will also investigate its usefulness as a control for Asian longhorn beetle and emerald ash borer."
Dr Glynn Percival, who heads Bartlett's Tree Research & Diagnostic Laboratory at the University of Reading, has worked with Arboricultural consultant Dr Dealga O'Callaghan to trial the technique, which involves boring an array of 10mm-diameter holes at the base of the tree and injecting the chemical at low pressure.
He said: "We tested for wound closure as well as leaf chlorophyll content and fluorescence - these weren't affected. We can inject it at quite high levels without burning the tree."
O'Callaghan added: "One application lasts two years, with signs of effect in three-to-four weeks."
Stressing the importance of controlling such pests, he said: "It's been a very bad year for OPM. It's often forgotten that it does a lot of damage to the trees as well.
"Nor is horse chestnut leaf miner just a cosmetic problem. Year on year it depletes the tree's energy reserves, making it susceptible to other pests and diseases, and will ultimately kill the tree."
"Can we eradicate OPM or HCLM from the UK? We can have a shot at it. You wouldn't have to hit every tree. For HCLM you might only treat high-value trees. But you'd need a coherent approach, which we don't yet have. Even if you don't eradicate these pests, with the help of the biological controls being developed at Kew we could keep them to critically low levels."
Dr Dealga O'Callaghan, arboricultural consultant.