red ants

give em some more water n then folllow them where they go when thye off ur plot and in the hedgerows then let em alone ... disturbance of any kind they dont like , clever things is ants  

They don't feed on actual crops, but their nest might be so close to root systems that those particular plants would suffer setbacks. And once the nest builds up to full force you'd have biting problems. The reds and oranges are far more fierce than the blacks and in quantity it could get unpleasant (just ask Digger Dave   ) It's best to discourage them from your patch and onto an area you don't care about.