I can't remember whether it was in a recent MGS journal or not but I read that to stop ants running up into your trees to farm aphids and the like, you should tie some cloth smeared with vaseline around the trunk. Both my lemon trees were heavily infested with scale insects of some kind last year. As the new growth is getting infested almost as soon as it comes through, today I gave the trees a thorough soaking with a neem oil solution and then applied the cloths. It remains to be seen how successful it will be. But the ants trying to go up the tree turned round and went away. Those coming down were totally confused. The last 2 photos show one brave ant trying to get across and then turning back. Fingers crossed.!