Sorry, another spud blight query

If it's only 1 spud it's more likely to be blackleg - there's a lot of it about this year!

Blight wipes the whole lot out rather than choosing one

I've lost five plants to blackleg this year. It comes with infected seed so buying certified seed from a reputable supplier is no guarantee. It's just one of those things and, as mum says, there's a lot of plague and pestilence about this year.