Cabbage aphid (Brevicoryne brassicae). A pale green or pale blue aphid found on crucifers and cabbage species.
The damage caused by aphids consists of weakening the plant: juices necessary for growth are sucked out by the aphids. This causes deformations of the leaves (bulges, curls).
The plant sap contains more sugars than the aphids can absorb; the excess is secreted in the form of honeydew. Ants, bees and wasps love it. A fungus develops on honeydew: sooty mold. Aphids also transmit plant viruses.
Where to find
Control
Control with pyrethrum, Insecticidal soap, soapy water spray, rhubarb spray or nettle spray.