Fire Ants on Brassicas (Broccoli)

I planted an entire row of brassicas and in hind sight it probably wasn't the best idea for pest management. Right now I have a problem with fire ants nesting and harvesting from the stalks of my brassicas, broccoli in particular.

What are they harvesting and how can I manage it? Are they harvesting the bi-product of another insect or nectar from the plant itself? Here is a photo of the fire ants carrying a small sap like substance from this broccoli stalk.

From wikipedia/aphids:

"Some species of ants farm aphids, protecting them on the plants where they are feeding, and consuming the honeydew the aphids release from the terminations of their alimentary canals. This is a mutualistic relationship, with these dairying ants milking the aphids by stroking them with their antennae."

Ants don't attack plants especially Broccolli. They're after aphids, and maybe the ants gone in the roots. Blockage on the roots can make  the plants die.

If you want them to move, just sprinkle some cinnamon. They’ll be gone in no time. Granted they will simply move but often that’s good enough.