My neighbours is as well, although there isnt anyone there at the moment but i get half the tree in my garden, so i'm only commenting to see what people say.

With permission, look around at other people's gardens and hedgerows for aphids that are swollen looking, and a light pearly tan. Those contain the larvae of a tiny stingless wasp that parasitizes aphids. Gently take leaves or twigs that have those wasp nurseries on them, and tie them to your tree with thread. The adult wasps that hatch out will each lay eggs in hundreds of other aphids, which will hatch out to lay more eggs, etc. After several weeks, most of the aphid problem should be gone. In the mean time, you can reduce the aphids numbers by spraying hard with plain water, once a week.