Ants all over my hop plant

[Northern_Brewer]

As I recall from school, the ants keep the aphids in special underground chambers in the nest when they're farmed.

That's only for root aphids, mostly species that attack grasses and some trees. On hops the main problem is the damson-hop aphid, Phorodon humuli which attacks leaves and stems - it's probably the biggest animal pest of hops in the UK, enough that Boadicea was bred specifically for aphid resistance.

I've never been much troubled by it but IME the fatty-acid sprays (the commercial version of detergent) work pretty well against aphids on other plants and are pretty specific to aphids so you're not going to hurt pollinators in the cross-fire.