Capsid bugs

There are several species of capsid bug, and most are harmless to plants. Those that suck the sap of plants, feed at the shoot tips, on very young leaves and on flower buds, causing damage as they do so.

Adult capsid bugs are either green or brown and around 6mm long (¼in). The young nymphs are usually pale green and, because they’re wingless, can’t fly.

The common green capsid (Lygocoris pabulinus) overwinters as eggs on plants. These hatch in spring, producing nymphs, which become adults by mid-summer. These lay eggs to produce a second generation before the onset of winter.

The tarnished or bishop bug (Lygus rugulipennis), on the other hand, overwinters as adults that find a sheltered place to spend the colder months. These lay eggs on plants in spring, which again produce nymphs and a second generation of adults.

This means that plants are mainly damaged from May to August/September.

The apple capsid (Plesiocoris rugicollis) overwinters as eggs laid in the bark of trees, which hatch in April or May. It only has one generation a year, timed to the production of fruit.

Many plants, but especially:

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• Apples and pears
• Caryopteris
• Chrysanthemum
• Clematis
• Dahlia
• Fuchsia
• Hydrangea
• Phygelius
• Rosa

Capsid bugs that feed on plants damage the cells where their relatively large sucking mouthparts have been. This produces a small, brown-edged hole, which enlarges as the leaves grow. Their feeding also causes the leaf to be misshapen, giving the foliage a distorted and tattered appearance.

When they feed on flower buds, the flowers may fail to develop or develop properly or open unevenly.

The apple capsid, which also attacks pears, feeds on the leaves and the young, developing fruitlets. This then develops into bumps and corky growth on the mature fruit. These are superficial and have no effect on the eating and keeping qualities of the fruit.

Check plants, especially those known to be favourite food plants, regularly and deal with capsid bugs as soon as you see them or any symptoms developing.

Unlike aphids, which tend to spend most of their lives feeding attached in one place on the plant, capsid bugs are very mobile and easily move around from plant to plant, feeding as they go.

Cut off badly affected growth to smarten up the appearance of plants.

Clearing up fallen leaves around affected plants may help remove the overwintering sites of the tarnished or bishop bug.

Capsid bugs sometimes use weeds as a secondary host, so keep weeds under control.

Spraying plants with insecticides containing the active ingredient acetamiprid, deltamethrin or lambda-cyhalothrin should help give good control of capsid bugs. Check that insecticides are approved for use on edible crops before spraying fruit trees. Most vegetables grow through or tolerate capsid bug damage and there usually isn’t any need to spray them.

Use plant protection products safely. Always read the label and product information before use. Plants in flower should not be sprayed due to the danger to pollinating insects. Either spray early in the morning or late in the evening when pollinating insects are less likely to be active.

There is nothing practical you can do to prevent capsid bugs attacking your plants.

• Insecticides
• Secateurs