I've got a bunch of ants farming aphids in my front yard, and also in one of the flower pots in my back yard. I'm generally unbothered by the damage to my plants, it's just nature after all. So long as the plants don't die, I'm okay with "sharing". The plants they're on seem unbothered as well, with a minor bit of damage to some leaves/flowers, but they seem to be growing strong and well, making plenty of flower buds and blooming abundantly regardless of the ants and aphids. So far, the ants/aphids mostly seem to be interested in the Leucanthemum vulgare and the two Coreopsis varieties I have in the yard/pots, and they seem to be leaving the rest of the flowering plants and a few bushes alone.
But I've had people tell me quite insistently that I need to go and get rid of the aphids and the ants because they will 'damage my plants'. So far, none of them have been able to explain just how much damage I can expect though. Will these aphids and ants eventually kill the plants they're on now, then move on to other plants, perhaps years from now? While there seem to be slightly more ants and aphids around this year, the plants they are on are also a bit bigger, so perhaps they're just taking advantage of the bigger 'farming area'? Or will this get out of hand in a few years? What is the 'worst' they can do to my plants?