Pests of box
This insect causes the leaves to become cup-shaped and in spring there are splashes of a waxy white material on the foliage which can also be blown around in the wind. In most cases the damage can be tolerated.
This moth has become established in south east England, and its caterpillars can completely defoliate plants. For more information and to submit reports of this insect visit the box tree caterpillar profile
Box leaf-mining gall midge
The box leaf-mining gall midge, Monarthropalpus flavus, is uncommon in Britian but occasionally heavy infestations occur. This tiny fly deposits its eggs in the new leaves during late April - May. The larvae feed inside the foliage, causing a yellowish discolouration on the upper leaf surface. The lower leaf surface develops a slight swelling in the area affected by the larva's feeding. The yellow larvae are up to 3mm long and they feed inside the leaves during summer – winter before pupating within the mines in spring. Several mines can develop in a leaf and heavily damaged ones often drop off.
Whilst the damage caused can be unsightly it rarely affects the vigour of plants and light infestations can be tolerated.
Mussel scale, Lepidosaphes ulmi, is a sap-sucking insect that is found on a range of woody plants, including box, apple, hawthorn, ceanothus, cornus and cotoneaster. The blackish-brown shells or scales are shaped like mussels, up to 3mm in length, and are attached mainly to the bark but sometimes they spread to the foliage. Heavy infestations can result in plants dying back.
Box red spider mite
A fine whitish mottling on the foliage of box plants can be caused by the box red spider mite, Eurytetranychus buxi, which is a mite that is specific to box. This tiny creature feeds by sucking sap from the undersides of the leaves, particularly during spring and early summer. By late summer infestations die out and the mite overwinters as eggs, which are laid on the stems and underside of leaves.
Box tree red spider mite is difficult to control. Fortunately, although the mottling may be considered unsightly, this mite does not cause serious damage to the plants and so it can be tolerated. If treatment is considered necessary mite numbers can be reduced by spraying the undersides of the foliage thoroughly with sprays based on fatty acids (e.g. Solabiol Bug Free, Doff Greenfly & Blackfly Killer) or plant oils (e.g. Vitax Organic Pest & Disease Control, Bug Clear for Fruit and Veg). Applications on three or four occasions at about five-day intervals when signs of renewed feeding damage are seen on new foliage may be necessary to control newly hatched mites and break the life cycle.
Do not spray on or near plants in flower due to the danger to pollinating insects.
Inclusion of a pesticide product does not indicate a recommendation or endorsement by RHS Gardening Advice. It is a list of products currently available to the home gardener.
When the leaves take on distinctive yellow tips or an orange or bronze colouration, it suggests the plants are under environmental stress.
Many shrubs can suffer brown leaves. Trying to diagnose the problem as soon as possible may help save the plant.