Box Tree Caterpillar
Has been a pest on Box plants for 5 years in the UK, but it has only arrived in Marlow last year as it progresses out from central London.
It is the caterpillar of a small night flying moth that will strip all the foliage within 2 weeks if not treated. Defoliated plants may recover but often die immediately.
Treatment is by spraying a protective insecticide in advance of the first eggs hatching which occurs in early May, or by spraying immediately caterpillars are seen. Several generations per year mean a long period of risk. Caterpillars and Pupae overwinter in webbing on plants.
Synthetic Pyrethroid sprays are very effective and give 4- 6 weeks of protection.
Biological sprays are also available that are specific for caterpillars, these sprays are a fresh product that work on contact and must be applied when caterpillars are present and within 2 weeks of delivery.
More information can be found here.