Capsid bugs are members of the true bug family Miridae, true bugs have sucking mouthparts. There are over 200 species of mirid bug in Britain. A majority feed on plant sap, most do not affect garden plants, some species are predatory. Some capsid bugs are a natural part of any garden. 

A few species do feed on plant

Sap is a fluid that circulates through a plant's vascular system, in a similar way to blood moving through our veins. Phloem sap carries the sugars produced in the leaves by photosynthesis down to roots and other storage organs, as well as carrying minerals and hormones. Xylem sap is watery and transports nutrients absorbed by the roots upwards to the rest of the plant. Some plants leak sap from wounds or pruning cuts, and this is known as bleeding.

Some capsid bugs have a more restricted host range such as the apple capsid (Plesiocoris rugicollis), which feeds on apple and pear and can affect fruits.

Signs of damage appear from May to early September.

• As capsid bugs feed, they damage and kill some of the cells where the mouthparts have probed 
• The leaves near the shoot tips develop many small, brown-edged, holes and may be misshapen
• Affected flower buds, particularly those of fuchsia, may fail to develop, or, in the case of chrysanthemum, dahlia and other daisy-like flowers, open unevenly
• Apple capsid (Plesiocoris rugicollis) damages the foliage and also feeds on young fruitlets, which results in bumps or raised corky growths developing on the mature fruit. These blemishes are superficial and do not affect the eating and keeping qualities of the fruits. Apple capsid can also affect pear

The presence of capsid bugs in a garden is not unusual, they are a component of garden biodiversity and are part of a functioning garden ecosystem.

• Tolerate some damage, by the time distorted leaves are noticed it can be too late to take control measures. Often the vigour of plants is unaffected and they soon recover. Vegetables do not need treating 
• Encourage predators and other natural enemies in the garden such as birds and ground beetles
• Apple cultivars vary in susceptibility to apple capsid – the fruits of Charles Ross’, ‘Allington Pippin’ and ‘Edward VII’ are some which may be extensively marked by capsid bumps
• If capsid bugs have been a problem in the past removing unwanted plants which can act as alternative host plants can reduce the problem
• Removing dead vegetation in late winter may destroy overwintering sites for the tarnished plant bug

• Apple capsid overwinters as eggs that are laid in the bark of apple branches and shoots, these eggs hatch in April to May. They become adult in June and July and there is one generation a year
• Common green capsid overwinters as eggs inserted into a range of trees and shrubs. They eggs hatch in spring and become adults by July. These lay eggs and produce a second generation before the winter
• The tarnished plant bug overwinters as an adult in sheltered places. They emerge in spring and lay eggs on a wide range of plants. There are two generations a year