[bayleaf]

I've read that if you put comfrey leaves in your potato trench it stops scab. Has anyone tried this?

[Potty Plotty Lotty]

It makes the potatoes grow better if you add the leaves as a mulch (or in the trench if you have enough leaves when the potatoes need planting)

Can't comment on the scab benefits though.

[bayleaf]

I'll take that as a no then!!

[mumofstig]

I wouldn't have enough leaves on my Comfrey at that time of year, even if I wanted to try it ...

John's advice for avoiding scab is here https://www.allotment-garden.org/vegetable/potatoes/potato-scab-common/

[Fishplate42]

As advised above, take a look at John's article which explains the actions you can take to minimise the effects of common scab. The marks you see on the skin are the potato's defence mechanism reacting to the bacterial infection. Peeling the potato will result in perfect edible flesh.

Adding comfrey, or any other fertilizer, will not make any difference to the susceptibility of the crop to the bacteria. This is a case where crop rotation will help. Growing potatoes in soil previously limed for a brassica crop will help minimise the transmission of the bacteria.

There is no chemical control available to us as hobby-gardeners, and I am not sure if there is one for the professionals either.

Ralph.     

[mumofstig]

Growing potatoes in soil previously limed for a brassica crop will help minimise the transmission of the bacteria.

Sorry, but that makes scab more likely
The RHS actually says

Common scab is worse on alkaline soil, so liming the soil to prevent club root of brassicas will predispose to common scab in potatoes. Apply lime after the potato course in the rotation

[Fishplate42]

Growing potatoes in soil previously limed for a brassica crop will help minimise the transmission of the bacteria.

Sorry, but that makes scab more likely
The RHS actually says

Common scab is worse on alkaline soil, so liming the soil to prevent club root of brassicas will predispose to common scab in potatoes. Apply lime after the potato course in the rotation

Thank you for correcting me. Sorry, I meant to say 'Not growing' as we always follow potatoes with brassicas on our plot, not the other way around for that very reason.

Ralph.