Topic: Whats wrong with my potatoes?

[tjamj]

Hi, i noticed today my potatoes have yellowing leaves with brown spots on them. Does anyone know what this could be? This is my first growing season so any advice really appreciated.

[nittynora]

Mine too ........ spotted one of the plants with this on during the last week.

Dug up the plant straight away - several decent spuds and lots of "embryos" that were marble-sized.  The resy look fine.

No idea what it was mind ............ ???

These are 2nd early - Charlotte.  The 1st earlies at the other end of the bed ( Pentland Javelin) look OK (dug 1 kg today - hooray!!)

[Flighty]

tjamj what variety are they and how long have they been in the ground?
If they've been in the ground at least ten weeks then  they're ready to dig up so why not have a firkle- a feel around in the ground with your fingers- to see what you can find.
Have a look on the Forum under Edible Plants as there are various threads about potatoes such as these

http://www.allotments4all.co.uk/smf/index.php/topic,52535.0.html

http://www.allotments4all.co.uk/smf/index.php/topic,52435.0.html

[manicscousers]

our red duke of york were the same, we've dug them up and got a potato sack full  ;D
think it just means the plant's had it

[PurpleHeather]

I would certainly have a look. Every one else's at this time has a load of clean and green foliage.

Never too early for blight dare I suggest?

[tjamj]

Hi thanks all for your replies. they are arran pilots.  i planted then around mid march. i had a quick feel around but the potatoes are still really small. great news about your potatoes though!
Will have a ook at some of the other threads.

[Tee Gee]

If I may highjack this thread and make an observation.

I have noticed that some people are concerned if the have blight on their potatoes or not and when they think they have; they dig them up.

If you meet such a position do not dig them up, just cut the tops off at ground level ( normal procedure for blight) and leave your potatoes in place and dig them up at leisure.

OK your potatoes may not bulk up any further but at least they will remain quite fresh.

Generally; the size/bulk of the potatoes will depend upon how long they have been growing prior to the affliction.

[Kepouros]

I`m afraid that I regard Tee Gee`s advice as a counsel of despair.  Provided that you notice the blight at an early stage there is no need whatever to cut the tops off, particularly when the crop has not yet started to bulk up - that simply means the loss of the crop.

By daily attention, and the exercise of some care, the plants can be kept growing for another 3 weeks or so after blight strikes.  Even if tuberisation has not been initiated when blight strikes, the resulting stress in the plant will bring this about, and the plant`s natural inclination to reproduce before it dies will result in greater effort being directed to tuber production.

The plant can in fact be kept alive and growing until over 70% of the foliage has been lost, and plants that had no crop under them when blight strikes can still produce a worthwhile crop.

I discussed this fully on this site some 2 years ago (with photographs) under a thread "Life after blight strikes"

[bronwylfa]

I would suspect a bit of blight, keep taking off infected leaves/stalks but do not compost them, bag them up and bin them.  This may enable the spuds to grow a bit more.  If the crop is growing near your maincrop spuds then I would sacrifice the lot and just eat very small new potatoes to try and protect the maincrop that do need to store well.  We didn't do this once and as a result, most of the maincrop potatoes were lost to rot, not a good year for us, we actually had to buy some, disaster!!!

[BarriedaleNick]

Optimistically thinking that this does not have to be blight.  It is early and I dont think any smith periods have been announced as yet.  (Asbean posted this link http://www.blightwatch.co.uk which seems a worthy site to sign up for.)  It could be lack of nutrients given that they have been in the ground for 4 months.  Got any pics??

[Digeroo]

yellowing leaves with brown spots on them

There are some tomatoes on our site looking like this.  I am fairly sure they are suffering from cold/wind damage.    Is the whole plant affected or just a few older leaves.   We have had a few cold nights

Blight site only showing problem in far end of Cornwall. 

[Tee Gee]

I`m afraid that I regard Tee Gee`s advice as a counsel of despair.

And I agree with you Keporous! but what initiated my reply was the urge of people to dig them up when in all probability, the crop may not have been affected by blight at all.

Personally!  like you, I would not rush into 'chopping the tops down' but when I saw that nittynora had dug their crop up I had to try and get over the other readers that this should not the first line of attack.

What I didn't make clear is I would only chop down the worst affected plants till ultimately I had cut down the lot.

And as you rightly said; The plant can in fact be kept alive and growing until over 70% of the foliage has been lost, and plants that had no crop under them when blight strikes can still produce a worthwhile crop.

So hopefully between the two of us we have clarified the situation.

[Tattieman]

I would say that alot of these yellow leaves and brown dots are that the plant is getting under stress due to dry conditions and a lack of feeding.
So far this year I have used 4 blight testing kits on :-

Leaves that were yellow with brown dots - Result was negative
Leaves that were green with black dots - Result was negative

The main problem was a lack of nutrients like magnesium. I used epsom salt and the problem has never came back.

I am also using a foliar feed and watering at night to keep them right.
I sprayed them all last night with their first coating of blight spray to prevent any problems.

Any blighted haulms we have in the fields are left to die and are sprayed heavily to kill any spores. Cutting and removing large patches of blight would only spread things further.

[davyw1]

Magnesium defficiency is yellowing of the leaves with brown spots between the veins

[attachment=1]

Early Blight the one on your right

[Deb P]

Last year I attempted to keep my tomatoes and potatoes going by adopting the removal of affected foliage method.....but I was amazed how quickly it spread, some whole rows 'melted' overnight so I gave up and chopped all foliage off in the end. Dug up unaffected tubers a few weeks later, and the toms did eventually ripen in the shed.... :-\

[shirlton]

I never knew that we should feed potatoes

[blisters]

Some of mine look like they have Magnesium deficiency.   Does it actually affect the harvest or is it more cosmetic.

[davyw1]

I think this is about the best link with a good picture
http://www.gardenersworld.com/how-to/problem-solving/magnesium-deficiency/

[Kepouros]

I fear that there is a risk of people making far too much of apparent slight magnesium deficiencies, and adopting quite unnecessary remedial measures.

We have, in the last few weeks, suffered the usual mix of english weather, of cold spell, hot dry spell, several days deluge, hot spell, etc.  For anyone gardening on the lighter or sandy soils this almost invariably results in plants exhibiting signs of apparent magnesium deficiency caused by temporary leaching out, or being unavailable due to potassium  levels, or cold or heat or whatever.  These problems are very often purely temporary and frequently cured by a change in the weather, when the apparent symptoms disappear.   Only if the the symptoms are so severe that the leaves actually start to die off would I noirmally want to reach for the epsom salts.

The same considerations can apply with several of the trace elements which, even when present in the soil in sufficient degree, can be made unavailable to the plant by soil conditions of temperature or dryness/wetness, and the answer is to treat the underlying soil condition rather that adding trace elements to excess.

[boltonlad]

Look on the underside of the leaf where the spots are I think there may be a few aphids knocking about on them, recently had to spray mine for exactly the same problem.  The first sign was the yellowing leaves, the second was the brown spots on the surface.  I found out what it is by checking in the veg and herb expert book, and as normal it was correct.