A product that claims to prevent box tree caterpillar damage is making waves in the UK horticultural industry following successful trial results in southern Europe.
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Box T Pro Press, distributed in the UK by Fargro, works as a mating disruptor. It uses a pheromone (the same that is used in box tree moth traps, but seven times more potent) that makes the zone around it smell strongly of female box caterpillar moths. Male moths cannot locate the real females, stopping them from laying fertilised eggs and therefore from producing caterpillars.
Box tree caterpillar is the bane of gardeners’ lives in public and private gardens, defoliating shrubs and topiary in a matter of days if not dealt with promptly. Currently, the best tool against it is the biological control Bacillus thuringiensis (sold in the UK as TopBuxus Xentari or BuxRevive). It does not harm wildlife or humans but needs to be sprayed on plants several times a year – not always possible due to low temperatures, rainy weather or time restraints.
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Some gardeners have also found success with Plant GP's natural box moth caterpillar treatment:
Box T Pro Press is currently only available for use by horticulture professionals with PA1 and PA6 spraying licences in the UK. It is pumped onto the woody stems of box, at intervals of 2m, or three doses per cubic meter of box. Once applied, it lasts for three months – so normally two applications would be required, in May and August.
Chris Poole, former chairman of the European Boxwood and Topiary Societies, has been pioneering use of the product in the UK, starting with a trial at the National Trust’s Ham House, from 2021. “The trial worked well, giving about an 80% reduction in visible damage to the hedges and cones across the property,” says Chris. “It also meant that we could relax a little more than usual when it came to spraying [with Bacillus thruringiensis]. It was possible to delay spraying until there was a clear run of dry weather. We were also able to spot spray just the areas that had been affected. Overall, it reduced our spraying from eight times down to three.”
Chris is now working as a specialist volunteer at Chiswick House & Gardens to further test the product, working under the guidance of Rosie Fyles, Head of Gardens. Chris’s strategy involves a treatment of Bacillus thuringiensis at the first signs of caterpillar activity, then placing pheromone monitoring traps around the garden, and applying Box T Pro Press at very first signs of adult box tree moths. So far, signs are positive: “No caterpillars have been found since the moths started flying a few weeks ago.”
Chris points out a couple of drawbacks: Box T Pro Press is not available to domestic gardeners and is expensive, at around £270 for 250 doses. “While it would have been good if it could be available to domestic gardeners as well, at least most larger public and private gardens will have access to someone who is qualified to apply the product. If not then a quick look at the European Boxwood and Topiary Societies UK website will find a member who can do the work for them: ebts.org/company-profiles.”
Ant Surrage, Fargro’s Technical Development Manager, says: "Using the Box T Pro Press as a mating disruptor showcases a breakthrough in combating the box tree caterpillar. It's an eco-friendly approach that disrupts the insect's life cycle, controlling its spread and reducing its destructive impact, without the need for harmful chemicals.”
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