blight

I watched Friday's programme, showing tomato blight, and inviting further comments from viewers on blight. I had potato blight earlier in the year, and cut down all of the foliage, but some of the foliage ended up on the compost heap by mistake, instead of being buried or burned. Does this mean all the compost is unusable, or if I leave it long enough will it become harmless? The foliage had only just started to turn, and the potatoes that we have dug up have been sound, though small, so the blight can't have got very far.

Late Blight, that which infects spuds and can infect toms, is a curious beast. The pathogen will live on on the affected produce - spuds or toms if they're left lying around - but not in the soil, and not on stems and foliage providing they're dead. If yours was LB, and the foliage went straight into the compost, I'd be wary.

I am indeed wary - worried even without the composting problem, as it's impossible not to leave any potatoes in the ground when they're as small as these were. I begin to wonder how anyone's patch ever recovers from these diseases once they've been introduced.

Well, providing the affected produce and plant material is removed and destroyed, and you plant certified seed spuds the next season, you're in with a chance. The LB pathogens don't live on in the soil. Any infection you get next season will be a new infection. The spores are airborne, travelling on the breeze, and they can travel miles.

I think Damson's concern is about the compost and what will happen if it is used on ground where potatoes or tomatoes are to grow.

I think it's nearly impossible to ensure that all your compost is free from anything that could have a trace of blight. I get rid of most of my blighted plants in the Council green waste bin, but there's always the odd late mini-potato, or blighted scraps of stuff that end up in my kitchen bin (which goes into the compost heap). I think I'd just forget about it and hope for the best.

As Italophile says, the infection is mainly wind-borne and will reach your plants when conditions are right no matter what you do.