Several of us have noticed lots of ants swarming up our apple trees. What’s going on? Are the ants doing any damage?

Ants unfortunately are a sign of aphid colonies, and aphids – green and black fly – suck sap, which is bad for our trees. We’ve also noticed a few curled up leaves, and these may also be the result of aphids. What can we do?

• First the mechanical solution: check both sides of the leaves  and squishany black fly and green fly between human fingers.
• Second the chemical solution: spray leaves with an organic pesticide based on ‘natural’ chemicals that will break down, such as pyrethrum or fatty acids. We have a spray available in the gated plot.

Aphids are a ‘normal’ part of our growing environment; we’ll try and control them, but they will return. It’s just a case of keeping their presence to a minimum so that plants don’t get weakened.

But having dispensed with aphids, back to the ants … What’s the connection? Ants and aphids are symbiotic. The aphids suck sap and secrete a sweet ‘honeydew’, the ants feed on the honeydew: a perfect relationship, perhaps, but not an equal one. It’s the ants that are the clever manipulators.

They literally ‘farm’ aphids – just like we farm cows – to ensure their honeydew supply. They will gently massage the back and rear end of the aphid to make it produce honeydew on tap. Ants also protect their ‘livestock’ by attacking aphid predators and will even nurture aphid eggs underground in their own nests. Once the aphids hatch out, their ant masters take them back to the host plant to continue producing the sweet, sticky stuff. Get rid of the aphids, and you should get rid of the ants …

More on aphids from the RHS.