True bugs (capsids)
There are manu different types of capsids, both harmful and useful. Harmful varieties include the common green capsid (Lygocoris pabulinus) and the common nettle capsid (Liocoris tripustulatis) that plague sweet pepper and aubergine crops, and the tarnished plant bug (Lygus rugulipennis) in cucumber crops. These insects are found in virtually all parts of Europe. They belong to the family Miridae, which also includes a number of beneficial species, such as Macrolophus pygmaeus (formerly known as Macrolophus caliginosus). Another harmful type is the sycamore lace bug (Corythucha ciliata), in the family Tingidae.
Capsid eggs are banana-shaped, cream-coloured and shiny, with a rounded, green cap on one end. The bugs go through five nymph stages. They feed by penetrating the plant with their proboscis. In greenhouses, these insects reproduce readily in damp, warm conditions, often being found in multiple adult generations. Adults crawl away after the summer. They are able to survive the winter in the greenhouse taking shelter in dead leaves and the like. The subphylum of these bugs is so large that it is difficult to give a general description of the appearance of the adult bugs. They generally have a flattened body, partially hardened wings and membranous underwings, like beetles. One way to tell them apart from beetles is the prominent triangular area on the abdomen that the wings do not cover. After moulting (particularly after the final moulting) they often change colour. The wings can generally only be clearly seen in the fourth nymph stage.
- Common green capsids puncture soft plant sections, leaving tiny holes that become large gaps in full-grown leaves and pockmarks in the vegetables. They cause growth deformities because the vegetable can no longer grow properly around the spots where the insects have fed.
- Nymph and adult common nettle capsids generally stay around the head of the plant, giving rise to thick, bunchy growth. The damage to the plant often remains for a considerable period, even after the insect plague has been eliminated.
- Nymph and adult tarnished plant bugs secrete a toxin when they puncture the plant, killing the area around where the bug feeds. This can be anywhere on the plant, from leaf to stem to axil. Once damaged in this way, the plant can no longer develop properly. Plants may drop vegetables affected by the toxin.