Aphid

Aphids, also known as plant lice, greenfly or blackfly are small plant-eating insects, and members of the superfamily Aphidoidea. Aphids are among the most destructive insect pests on cultivated plants in temperate regions. The damage they do to plants has made them enemies of farmers and gardeners the world over, but from a purely zoological standpoint they are a very successful group of organisms.

Protection
There are various chemicals that can be used for controlling aphids. Nowadays, there are many plant extracts and plant products that are eco-friendly and are a more effective control of aphids. Another common alternative option is Biological Control, a system in which a natural predator, such as a Lacewing is introduced in egg form, the larvae of which eat aphids, bringing down aphid population. The adult lacewing survive on pollen, which leaves the crop without threat.

Companion Planting
Alliums, anise, buckwheat, catnip, chervil, coriander, dill, mint, nasturtium (not blackfly), petunia, poached egg plant, rue, summer savory, sweet alyssum all repel aphids or attract predatory insects that eat aphids and can be used as companion crops by planting them next to plants that suffer from aphid attacks.

Nasturtium (blackfly) and sunflower attract aphids and can be used as sacrificial crops (although sunflowers are strong enough to withstand the aphids).