Kirva

Kirva is the Finnish common name for aphids, small soft-bodied insects in the superfamily Aphidoidea, order Hemiptera. They feed on plant sap using piercing-sucking mouthparts. Most species range from 1 to 4 mm in length and come in colors including green, yellow, black, or pink. They excrete honeydew, a sugary liquid that can foster sooty mold and attract ants.

In many aphid species, reproduction is parthenogenetic, allowing rapid population growth; winged forms can disperse to new hosts when populations become crowded or plants are stressed. Some species have holocyclic life cycles with alternation of hosts: over-winter eggs on certain trees, giving way to a herbaceous summer host; others are anholocyclic, reproducing on a single host year-round.

Aphids are significant agricultural pests because they suck sap, stunt growth, curl leaves, and transmit plant viruses such as Potato virus Y and Barley yellow dwarf virus. Their honeydew also supports secondary infections. They have many natural enemies, including lady beetles, lacewings, and parasitic wasps, and are a central target of biological control and integrated pest management.

Management includes regular scouting, promoting beneficial insects, using reflective mulches, row covers, and, when necessary, targeted pesticides such as insecticidal soaps or oils. Broad-spectrum insecticides can disrupt natural enemies and worsen outbreaks.