Q What do capsid bugs look like?

A Capsids look like small beetles with long legs and antennae and are about 6mm long. They move quickly if disturbed – hiding in vegetation or dropping to the ground. They vary in colour from green to brown. When the wings are folded they form a diamond shape on their backs.

Caption: Capsid bugs attack a wide range of plants

Q What are the main types of capsid bug?

A There are four types of capsid which are important pests of garden plants:

Apple capsid (Plesiocoris rugicollis) overwinters as eggs laid in the bark of apple trees. When they hatch in spring, the young bugs feed on the rosette of leaves around the blossom buds. Feeding marks can often be seen on these leaves. They move on to the developing fruitlets and new foliage later. By July, the adults begin to lay their overwintering eggs. Apple capsids come into the garden from willows which are their natural host plant.

Common green capsid (Lygocoris pabulinus) overwinters as eggs, hatching in April. After feeding for a few weeks on the woody plants where the eggs spent the winter, they move to herbaceous plants. By mid-summer the winged adults hatch. A second generation develops from eggs laid in June and July. They feed until the autumn when they pupate, emerging to lay overwintering eggs on woody plants.

Potato capsid (Calocoris norvegicus) is less important than the others and is an occasional pest of daisy family plants, especially chrysanthemums.

Tarnished bug or bishop bug (Lygus rugulipennis) adults overwinter in plant debris, especially heaps of garden rubbish. In May, they lay eggs in plant stems and flower buds. Little damage is done by the first generation. By late summer the second generation attacks many garden plants, before the onset of autumn sends them into hibernation.

Q Could I mistake capsid-bug damage for anything else?

A Many other insects, mites and eelworms cause similar damage to capsid bugs. Also, by the time problems are noticed, the capsid bugs have often moved elsewhere.

Q How do I know whether capsid bugs are present?

A Other signs are spots of brown, calloused material where the plant was pierced by the capsid mouthparts. These spots are often hollow, and become enlarged, with tears around the edge as leaves expand and grow. Distortion and puckering of attacked leaves is common too. Where the growing point has been attacked, the whole shoot may be distorted or even killed. Flowers can be similarly affected.

Q How do capsid bugs damage plants?

A During feeding, capsids inject toxic saliva into the plant tissue, which kills the cells near to where they are feeding. They feed on young growth which develops visible signs of damage as it grows. Affected parts become distorted and the areas of dead tissue tear into tiny holes. If the flower buds are affected (as often occurs in hardy fuchsia) the flowers may fail to develop. The least serious damage is caused to fruits. On apples, damage results in raised corky pimples or blotches on the skin. On pears, look for small depressions with corky outgrowths. The fruit is still edible.

Q Is capsid-bug damage on apple trees serious?

A Capsid feeding on the leaves of apples cause only minor damage and should be tolerated. However, damage may be more serious on trees that have been recently planted or are already lacking vigour, because the capsid bugs will weaken the tree further.

Q Can I avoid capsid-bug damage on apples?

A It is not possible to eliminate the chances of damage altogether, but vigorous, healthy plants are more likely to escape capsid attacks. The fruits of some apple varieties (eg 'Allington Pippin', 'Charles Ross' and 'Edward VII') appear to be more susceptible to capsid attack than others, so are best avoided.

Q Which plants do common green capsids attack?

A The common green capsid attacks a wide range of plants. These include vegetables (like beans and potatoes), most tree and bush fruits (especially apples, raspberries and blackcurrants), herbaceous plants (like salvia), trees (such as magnolia), climbers (eg clematis) and shrubs (eg caryopteris, forsythia, fuchsia, hydrangea and roses). They can attack and stunt seedlings, and bedding plants, pelargoniums, dahlias and chrysanthemums are often damaged.

Q Are all these plants at risk from capsid bugs at the same time?

A Trees and shrubs are host to overwintering capsid eggs, so the newly hatched nymphs feed on them first during April and May. The nymphs then move to herbaceous plants, on which they feed until June and July when they develop into adults.

Q What plants do the tarnished bugs attack?

A The tarnished bug’s main hosts are chrysanthemums, dahlias, nasturtiums, poppies, zinnias and asters. Weeds, such as nettles and groundsel, are also affected.

Q Can I reduce the likelihood of capsid-bug attack?

A Since capsids not only attack cultivated herbaceous plants, but will also feed on herbaceous weeds, keeping weeds to a minimum will help to reduce the number of alternative host plants. Tarnished bugs overwinter as adults in hollow plant stems, hedges and leaf litter. Herbaceous plants and other debris should be cleared up if possible in late autumn to reduce the number of overwintering sites for capsid.

Q Is it necessary to control capsid bugs?

A If there is only minor damage to leaves, flowers or fruit it is not necessary to control capsid bugs. Damage on vegetables is rarely severe, though seedlings can be stunted and some control will be needed. When symptoms are severe on ornamentals and whole plants become disfigured and distorted, it may be desirable to take control measures.

Q How can I control capsid bugs?

A Getting rid of dead foliage and plant debris, and keeping down weeds, will help reduce the likelihood of capsid bug damage. Fruit trees and bushes can be sprayed immediately after petal fall and other plants can be treated as soon as you notice the damage. However, the capsids will usually have disappeared before you manage to spray, so it's probably not worth it. Try chemicals containing pyrethrins.