A few of my potatoes have what I think is potato blackleg. The haulms have gone yellow and collapsed and the stem is black and gungy just above soil level. I've looked in a few books which say that it cannot be passed from plant to plant. However, they also recommend taking out the affected plants as soon as they are noticed. I am a bit worried that if I pull up the blackleg plants I might disturb the healthy plants around them. Can I wait until I am ready to harvest the crop before taking them out?