IRL, the ants can't do anything to the ladybug but to annoy the heck out them, and the ladybug gonna bulldoze through the ant guards anyway to eat the aphids. Things change, however, if the ladybug gets surrounded by multiple ants-they're at risk of being attacked; or worse, eaten. Since aphids reproduce VERY quickly via parthenogenesis (i.e cloning themself) once or twice ladybug raids won't do anything to their population.
As long as the ant can secure a broodmother, they can continue farming the aphids for their dew sap.
Very clever: trouble is he makes them all so damn cute, one doesn't know whom to keep one's fingers crossed for: the aphid, the ladybird or the ant.
I understand rose-growers hate aphids, but that's all I know about them.
The danger of aphid infestation is that they multiple in warp speed (literally).
A healthy aphid can produce 1-12 clones per day. Which means your aphid problem will only increase EXPONENTIALLY if left unchecked, and it can cause an entire field of plants to suffer from either stunted growth or death.
Any farmer hates aphids, especially herb-vegetable farmers like tomato. Aphids can wreck your tomatoes by preventing flowers to turn properly into fruits; which is why you should place potted mint plants (aphids hate the aromatic compounds in mint) around your tomatoes, that way if the ants brought aphids to snack on the tomato plant they will scatter away.
