Topic: common scab on pots and beet

[minerva]

All my potatoes were infected with scab this year, they were planted in three totally seperate locations but still became infected, and my beetroot as well, they are still edible and taste good, but I would like to avoid this problem next year?  someone said it could be Boron defeciency but when I looked around I cann't seem to find any more info on this and how to increase the boron in the soil, infact i had not even heard of it before.  can anyone help me with this
sam

[Mrs Ava]

Scab on beetroots  :o  I dispair!! I am begining to think we need a first aid section on this site, with a list of symptoms, diagnosis's's's and  cures.  I didn't realise there were so many pests and diseases covering virtually everything I could ever want to grow!  
So....scab....doesn't actually affect the edibility (is that a word!?!) of the root?  What does it do to the plant?  And how would I recognise it?  :-/

[minerva]

well I think its scab!  the beets are covered in scabby lumps that are slightly darker just like the potatoes, thought they are only skin deep, I should have taken a photo but they are now all pickled in jars awaiting Christmas delivery up to family in cheshire, (They just love my home made christmas prezzies!!!??) :-/

[Hugh_Jones]

Potato scab is a bacterial disease, and its appearance is usually the result of lime in the soil, or overdry soil while the tubers are growing - a definite possibility last summer.  While you may indeed have a boron deficiency in your soil, this would not normally manifest itself in the form of scab; the usual early indications of boron deficiency are a stunting and deformation of the stems and foliage to the point where growing points may die out and stems die off (and no way could this be mistaken for potato blight).  Oddly enough, one of the main causes of boron deficiency is high alkalinity in the soil, and this would almost certainly be remedied by a reduction in the pH level.

I would suggest, therefore, that you do a pH test on your soil (in several places) to see whether the cause can be alkalinity (never lime before potatoes), as well as deciding whether the soil could have become overdry at the critical time.

I regret to say that I have never heard of scab on beetroot - neither have any of my reference books - so I can only say (as I did re potato scab) that boron deficiency would be unlikely to manifest itself in this fashion.

[Palefire]

My potatoes had a mild smattering of scab this year and it was my first year of growing them. It seems from your description that the culprit was the incredibly dry summer, especially as the soil was rather dry around the tubers when I lifted them.

Another learning curve journeyed by myself this year was that it does have an effect whether you get your spuds in at the right time, too. There was a four week gap in the timing of my Cara, due to lack of time in the garden, and the second set only yielded as much between them as the first set did per plant!

All part of the fun.

Love, Palefire

xxx

[Hugh_Jones]

Palefire, the reason why your late planting of Cara was less productive is that Cara is a maincrop variety.  Unlike the first and second earlies (which crop when the plants themselves are ready whatever the date) the maincrop types are sensitive to the length of daylight, and the size of the crop will always depend on the amount of topgrowth made before midsummer`s day - as soon as the days start to shorten production of tubers will commence, and if the topgrowth up to that date is poor, so will be the crop.

Of course, if your soil was dry as well this would only make matters worse.

[Palefire]

Thanks, Hugh - yes it was the late  planting that did it (regarding the yield) - I saw how well the first lot were growing and I resolved to get a few flowers in an adjacent bed out the way of a second lot, but of course, time ran away with me. I will try harder next time, as the potatoes themselves are lovely and they are still keeping well in a dark cupboard in my garage. :)

Love, Palefire

xxx

[minerva]

:) thanks for the help, dry weather seems much more likely,  and I suppose i shouldn't believe everthing kindly looking old men down the allotments tell me!
 I would love to get some scab free pots next year, I am too embarrased to give any of mine away this year as they look totally unedible and would probably get thrown away by the over sanitised recipients, they do taste good though,  are there any good scab resistant verieties to try??
sam
xx

[tim]

- do what the s/markets do - wash them before you give them away. The scab just washes off! Or, at least, it does with ours.

You did tell us, Hugh, but where did you get  your expertise? Not Porton Down, I trust!! - Tim

[gavin]

Hi there

All good advice so far re water and lime. Just one other little trick for scab-free potatoes.  When you dig the trench, put a layer of newly cut grass in.  

It was explained to me that the bacteria would head for the grass rather than the tatties.  So I'd have scabby lawn cuttings at the end of the season, and scab-free potatoes.  

Sorry, I can only vouch for the scab-free potatoes - even after this dry summer!!!

All best - Gavin

[Hugh_Jones]

To reply to 2 of the above postings:-

Minerva - Yes, there are several scab resistant varieties:- First Earlies - Accent and Princess; Second Earlies - Kondor, Celine (my favourite) and Bernadette; Early Main - Pomeroy and Naturella; Late Main - Verity (which is a Cara type).   Princess and Bernadette are both excellent Salad Potatoes.

Tim - Slight Scab can be washed off as you say, but moderate to severe Scab eats heavily into the skins and thoroughly disfigures the tuber.

And as to your enquiry, no I didn`t tell you, and if I did you would no longer have the pleasure of wondering.

[minerva]

;D  thanks for the scab free advice hugh  Gavin and Tim, I can now go and look throught all my catalogues with my allotment buddy (we are shareing all our seeds this year to cut costs) and actually sound like I know what i am talking about for once,  My pots didn't clean up when i washed them you actually have to peel quite alot away to get rid of it never mind i can usually get the boyfriend to do that, as long as i cook them!
what about those pink fir pototoes? are they scab resistant, I think I am going to have an ongoing problem with this as my plot is very fine soil on an open south facing slope so there is never enough water in the soil, I have been digging in lots of horse poo! hope that helps
sam
xx

[Hugh_Jones]

I`ve never grown Pink Fir Apple, but one of my neighbours did, and his got mild scab - but again that may have been due to very dry soil (he`s on a water meter, so he refuses to water).

[gavin]

Hi - I tried 4 Pink Fir Apple potatoes this year.  Not a great yield - probably because of the dry summer; I should have watered a lot more.

But not a trace of scab on them - even though the soil was dry.  Could be me putting grass in the planting trench though.

All best - Gavin

[tim]

- yes of course, Hugh - I was looking on the bright side!

Pink Fir - we' ve  never had scab. Yield? The 'blessed' rain came far too late - we only managed 2 sacks from 50'.

Trying Anya next year. - Tim

[john_miller]

For Minerva:- It is not impossible that your kindly old men down the allotment were entirely wrong. Adequate amounts of boron are associated with suppression of bacterial cankers (which is what scab basically is) on plants susceptible to them.
 The acid test for boron deficency in crops where the storage organ is harvested is the presence, or absence, of hollow heart or brown heart. This will only be apparent when the root is sectioned. However boron deficency is excerbated by dry conditons (it is not very soluble) or, as Hugh mentions, by high pH.
 Boron is an integral part of starch cell formation (as in potatoes, swedes, sugar beets, celeriac) and, unfortunately, peak demand for this nutrient in these plants coincides with the driest time of year. Low levels can be remedied with Boraxo or Solubor but it also easy to induce boron toxicity by overapplication.

[john_miller]

Oops, make that exacerbate, not excerbate.

[tim]

- throw a pebble into the pond  and you sure get a ripple!! - Tim

[john_miller]

 If I am understanding you correctly you had brown cells inside the potato describing a heart shape but no actual hollowness? If so, then this could be the inital stages of hollow heart although any number of other reasons can also cause cell damage. Perhaps moisture came along at just the right moment to enable some cells to continue expanding instead of dying. True hollow heart is just that: the centre of the tuber or root is hollow and will, in potatoes, be surrounded by a layer of brown, dead, cells. Due to the way the cells are laid down during tuber expansion the hollowness tends to be elongated along the long axis of the tuber.  In my experience swedes, for instance, can then be infected by secondary pathogens causing the insides to be become a pungent slime which expands out to the pith. Not pleasant to stick your hand into!
 When I said the acid test for boron deficency is hollow heart I meant that in the colloquail sense. The real acid test for boron deficency is literally that- tissue analysis in a laboratory. Anyone got deep pockets?
 My uncles produced seed potatoes in Northern Scotland. Golden Wonder was their favourite potato. They had a muck soil, very moisture retentive as a result, but when I tried growing them on the London clay where I grew up they were, like yours, very fibrous and, frankly, inedible. You may want to look for a different cultivar?

[john_miller]

North East Scotland? Fraserburgh specifically?