Aphids are very tiny soft-bodied insects which suck juice from cabbage family plants.
There are many plants in the cabbage family, they include broccoli, brussels sprouts, cauliflower, chinese cabbage, collards, kale, kohlrabi and of course the common cabbage and all are susceptible to aphid damage from brevicoryne brassicae, the cabbage aphid. Aphids typically have very pale, light green bodies which can often appear grayish because they are so pale. They are soft-bodied insects and can be found on cabbage family plant leaves and stems. They are most commonly found on the undersides of plants in the vegetable garden, but may also be found on the actual heads of the cabbage family plants. In small numbers, you may notice very little plant damage, but in large numbers aphid damage will appear in the form of yellowing leaves which tend to wilt in a downward direction.