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Potatoes in bags
prowboth
Posts: 6
I have grown potatoes in bags for a number of years - mainly king Edwards and charlotte. I use bought compost. This year for the first time I have had a real problem with scab. How can I reduce this problem.
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Posts
Prow: what have you done with the compost after harvesting the potatoes? I would be concerned about the compost being host and if sprinkled back into the garden could cause problems.
Is it common scab or powdery scab? I don't think there is a chemical cure.
I think (I'm no expert) common scab is often caused by drought (powdery I think becoming worse under overly wet conditions) and is worsened by alkaline compost so you could test the compost (and chuck a handful or two of lime into it when preparing as required).
Aside from that all I can think of is when you plant next year take a really good look and discard any looking like they might be displaying signs of scab.
I put the compost on my flower beds.
Scab on potatoes is caused by a bacterium in the soil and is worse in alkaline soils. Lime is often added to multi-purpose compost to reduce the natural acidity. The chances are that the seed potatoes you used were already carrying some bacteria and the compost you used this year just happened to have more lime in it than usual. I would buy your seed potatoes from another supplier next year and use a different brand of compost. The chances are they'll be fine.