Aphids

Organic control:

Ladybugs are the prime aphid predator. Aphids aren't a problem, they're a symptom.

Aphids are a great indicator of imbalanced fertilization. Usually showing an excess of nitrogen. In one case of a lemon tree, the only one in a lemon orchard, that was infested with aphids, it turned out that the owner urinated at that particular tree every morning...hence, high nitrogen. Aphids are present to solve a problem, think of them as "nature's pump", boring in to suck out sap and slow down the plant. The plant has too much nitrogen, which pushes the growth excessively.

On fruit trees, after a pruning cut where active growth of new shoots occurs, aphids may be present.