what disease does my potato have (picture)?

[nmayhew]

hi there,

we have grown potatoes fairly successfully on the same plot for 2 years, and this is the third (rotation next year).

they are not fed much and generally not "loved" but have come out ok in the past

however the first few plants we dug up looked like this - any ideas?





the spud pictured has been put back together after i cut it so you can get a feel for general shape and appearance, in case you are wondering why you see a "join"!

many thanks

Nick

[SarzWix]

Are you saying that you've grown them in exactly the same place for 3 years, but will grow them in a different place next year?

From the first picture, it just looks like scab, which is caused by a lack of water and also possibly the soil being too alkaline. However. I've never seen scab affecting the tuber on the inside, so I could well be wrong.

[nmayhew]

hi,
yes 3 years on same raised bed in the patch, 2 years were fine - this year there seems a problem

[womble]

You're supposed to rotate every year, not once every 3 years.

[SarzWix]

As Womble says, you shouldn't be growing them in the same patch really. And that might well be the cause of your problems. Although pest/disease prevention is one of the main reasons to rotate, there is also the consideration that the plant will have used up all of it's 'preferred' nutrients from that patch, and moving them around gives the chance for them to build up again through the application of compost/manure/fertiliser etc while different crops are using different nutrients.

NB. When a book or an article says "A 3 year rotation", it means that it takes 3 years before the same crop comes back to a bed, not 3 years before you move it on. HTH

[Jeanied]

It looks like brown rot - and will affect potatoes grown in the same ground for some years to come. No idea how to treat - exept grow them somewhere else next year!

[SarzWix]

Sorry to disagree Jeanie, but brown rot usually shows in a more circular form:

[nmayhew]

just a quickie to say thank you for your input so far (although no positive ID on the disease yet?)

i DO know you are meant to rotate every year, just didn't have time / inclination to do it!

[Nicos]

Did you have any signs of early blight????...just a thought

I found this site- but none of them are quite the same....

Résultats Google Recherche d'images correspondant à http://vegetablemdonline.ppath.cornell.edu/Images/Potatoes/Detection/PotatoDetectColl2.jpg

[tongegardner]

The first picture could be scab if the patches have ragged edges but it looks more like the early sign of Blight - has it been very wet and warm where you are and has the foliage been affected in any way?
However as everyone else has noted, you must move you spud bed on every year to avoid soil born pests and diseases being built up in the soil.

[OllieMartin]

As I'm at work I can't see the images, but you can compare to a whole host of troubles here:

Potato troubles - WikiGardener

[teakdesk]

I'm reasonably sure that is blight.

Nothing to do with the soil - although the fungus can overwinter in the soil it is normally spread by the wind.

What was the top growth like before you harvested?


There is some scab on the tuber but the "bruises" on the outside of the ends of the tuber look just like blight as does the markings inside the tuber.

Moving to another plot next year, preparing the ground to minimise scab and picking a variety of potato that is resistant to scab will help with that (although tubers with scab can be eaten) but very little will help against blight.

[SueA]

There's a photo here of what blight in a potato tuber looks like, it looks more extensive than the rot you have in yours but I suppose it could be a different stage. Did you have any signs of blight on the foliage?
Potato Blight - Identification and Treatment of Potato Blight, Blight Resistant Varieties

[teakdesk]

l think these photos show it is blight - the pics with the red border are blighted tubers and the others are from nmayhew. The outsides have the same bruises and the inner the same rot, although those of nmayhew are not quite as advanced.

[nmayhew]

thanks again guys for your continued help
i guess blight it is!

having said that i dug up some more 2 days ago (adjacent to the affected ones) and 6 out the 7 spuds were fine, the one having only very minor signs

fingers crossed i get at least half of them that i grew

will remember for next year, and also grow on a different patch!

happy gardening and thank you all again

Nick