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- Sep 4, 2011
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To be honest I think the worries about late blight being "in the soil" are significantly overstated. As I understand it the fungus needs a live host to survive and the spores aren't viable for very long without one. That does mean however that "volunteer" potato (and perhaps tomato) plants can act as a reservoir of disease from one year to the next and I suspect that's where the concern about survival in the soil has come from. Either that or confusion with early blight, which apparently can survive in the soil over winter though I've never seen it on my plants. I am now very careful to remove all tomato and potato plants that self-seeded or grow from potatoes that I missed harvesting the previous year. There are also other plants in the nightshade family (some of which are weeds I think) that can be infected by the fungus and allow it to spread much more quickly.
By far the bigger problem in this country would appear to be that the spores from infected plants can apparently be carried many miles (even tens of miles) on the wind, which is why growing under cover helps, I guess. Given the climate in the UK there may also be sufficient moisture in the air for the fungus to flourish even if the leaves of the plants don't get wet otherwise, which is probably why the plants in my polytunnel eventually succumb given that it's usually fairly damp here by late October.
There is a spore type that can be produced by the late blight fungus that may be able to survive over winter in the soil, but I don't believe it has ever been found in the UK.
James
By far the bigger problem in this country would appear to be that the spores from infected plants can apparently be carried many miles (even tens of miles) on the wind, which is why growing under cover helps, I guess. Given the climate in the UK there may also be sufficient moisture in the air for the fungus to flourish even if the leaves of the plants don't get wet otherwise, which is probably why the plants in my polytunnel eventually succumb given that it's usually fairly damp here by late October.
There is a spore type that can be produced by the late blight fungus that may be able to survive over winter in the soil, but I don't believe it has ever been found in the UK.
James