The RHS is keen to hear from gardeners who find the pest in their garden so that it can build a picture of host plants in the UK and tailor advice to gardeners.
Magnolias, mulberries, elders, sycamores and dogwoods are thought to be a favourite. Gardeners are encouraged, where practical, to remove egg masses with a stiff brush and water.
An RHS spokesperson said: “Given that many plants are grown for their blooms, foliage or textured stems and branches, the pest could certainly lessen their enjoyment.
“If it proves impossible to remove [with a brush and water] and its aesthetics are considered too much to bear a pesticide can be applied strictly according to label instructions, this is likely to be most effective when the eggs hatch in summer.”
Pests which mar and destroy gardens have been brought in from abroad in recent years, sometimes to devastating effect.
The RHS identified one new plant disease last year – a Phytophora on a Water Iris – and in previous years their identification includes deadly diseases which have taken hold in gardens across the UK, including Box blight in the 1990s, Escallonia leaf blight in 2007 and Kerria twig blight in 2014.
The Fuchsia Gall mite, discovered in the UK by the RHS in 2007, is now causing real problems for fuchsia growers in the South East.