I need HELP!

My chard plants are inundated by black aphids and ants that seem to be farming the aphids. Every single new leaf that emerges is almost instantly colonized on the back side of the leaves by these black aphids, causing the leaves to curl. There are so many aphids that the back side of the leaves are black. Growth of course is stunted. I don't know what I should do.

The first crop grew nice and strong with big, healthy leaves. Subsequent crops are now struggling. I had no aphids last year but this year they're fierce.

Any help would be appreciated.