I have ants farming aphids on my stepover apple tree. The tree has only been in about 2yrs and has yet to fruit. The horizontal branch is only about 6" from the ground and i have tried the Vaseline method I found in an old discussion on this site with no success. Can anyone advise? unfortunately i am on a terraced slope positively teeming with ants but they do not seem to bother with my other stepovers or cordon trees.