Allotments 4 All
Produce => Pests & Diseases => Topic started by: Rhys on September 02, 2006, 12:10:36
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I have a bad case of some sort of rot on my 2nd earlies - Maris Peer - there is a lot of wastage.
Having looked up on the internet it looks like brown rot or ring rot and the cause can be from the seeds, apparently. I bought my seeds from a garden centre which said 'basic scottish seed'.
Has anyone ever had this problem and will it persist in the soil do you think?
(http://burgundy-breaks.tripod.com/poot1.JPG)
(http://burgundy-breaks.tripod.com/pot2.JPG)
(http://burgundy-breaks.tripod.com/pot3.JPG)
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Without wishing to appear to give any indication of certainty I don`t think that it`s either. The symptoms of both Ring disease and Brown Rot closely follow the vascular rings of the tuber, while those shown in your pictures appear to be more haphazardly spread.
Were there any signs or indications of trouble in the foliage of the plants before you lifted them, or are there any discolourations or softish or sunken spots or lesions on the skins of the tubers which might give more of a clue? In particular, were there any foliar indications of blight, and is there any smell from the tubers?
Both Ring Diseases and Brown Rot are notifiable diseases, so it is most important to try and identify what you have.
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if the haulms looked ok, i.e. not blighted then it could be a mineral deficiency, called spraing I think :-\
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Spraing's not a mineral deficiency, it's caused by viruses (either tobacco rattle virus or potato mop top virus) and is pretty nasty. If it's the tobacco rattle virus, it's transmitted by nematodes and is pretty much impossible to get shot of.
If you're worried, it might be worth emailing a close-up high def photo to somewhere like the RHS if you're a member. They may also take samples in that case.
http://www.csl.gov.uk/prodserv/diag/potato/Soil_testing_spraing.cfm
These folk do testing for commercial growers, given the cost! The link does have photos. Perhaps they'd advise a lottie grower if you contacted them and said you'd got a photo?
moonbells
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have been digging deep in the memory cells to remember what I was taught and should add that whether it is a virus thing or not a mineral deficiency can herald the onslaught of such a condition in spuds
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I guess like lacking vitamins can make us more susceptible to viruses. Makes sense.
(Except I bet most veg gardeners never have problems with malnutrition!)
moonbells
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Calendula, is it possible that you are thinking of boron deficiency - hollow heart or brown heart in potatoes and swedes (the only mineral deficiency I can think of likely to affect the tubers in this way)? Or are you thinking of PLRV or the X and Y viruses. The damage doesn`t seem to look quite right for boron deficiency, but certainly shows some similarity to PLRV, I had considered all of these, and that`s why I asked about the foliage. Any mineral deficiency or virus resulting in this damage would most certainly show at least some unusual signs in the foliage or stems.
Where is John Miller when we need him?
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could it not be the early stages of soft rot? the distinctive aroma would be a give away... but doesn't come across too well in photo's...
???
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Soft rot starts from the skin and works inwards. This doesn`t seem to be the case from the photos, but they`re not entirely conclusive - again one reason why I asked about soft spots or lesions on the skins.
Without some more input from Rhys we`re left scratching our heads!
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it is a very fine balance isn't it, even a water shortage such as we've had could cause this and the haulms can look fine above ground but the real problems occur underground - if there is no awful smell then that would rule out blight or rot, there are some varieties that are susceptible to spraing more than others, not sure if MP is one of them - either way I would choose another supplier, check your soil, don't grow spuds there for awhile, maybe look for other telltale signs of disease, try and find out if that variety has had a poor show nationally (that will make you feel better :)) and hope for something good next year
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If Rhys wants complete peace of mind the Central Science Laboratories will test for TRV, Ring Rot or Brown Rot (for a fee of course).
I agree that she should change her supplier, and grow next year`s crop as far away from this year`s as possible.
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The foilage was good with no signs of blight.
There is no bad smell whatsoever and there are no soft spots or lesions - in fact the potatoes look perfect, its only when you cut in to them you can see they are bad.
Perhaps it was because of the wet spring. I planted the potatoes and then it rained for about 4 days straight after. The foilage emerged slowly and growth seemed stunted.
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what was the soil type like and did you manure at all and can you say where you bought the seeds from
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The symptoms which Rhys describes (or rather the lack of them) seem to rule out TRV. The only foliar symptom of TRV is a yellow mottling of the foliage, whereas the only symptom of Rhys`s potatoes was an initial stunting of the foliage. To me this suggests either eelworm (which wouldn`t cause the tuber damage) or boron deficiency symptoms, which would cause a stunting of the stems and an upward curling of the leaf edges. Admittedly the tuber damage does appear entirely like that of boron deficiency induced brownheart, but then I`ve never actually experienced it `in the flesh` and can only rely on the pictures in my manual.
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what was the soil type like and did you manure at all and can you say where you bought the seeds from
I added pelleted chicken manure and I bought the seeds from my local garden centre - I think there is a name, will check tomorrow.
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Pelleted chicken manure has a fairly high calcium content (usually about 8%). One of the effects is to make the boron in the soil unavailable to the plant, as well as contributing to scab in susceptible varieties.
I still go for boron deficiency symptoms. This does not necessarily mean that your soil is deficient in boron, merely that you may have made it unavailable. Boron is also not very soluble, and the effect of the summer drought would have been to exascerbate any calcium induced deficiency.
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Pelleted chicken manure has a fairly high calcium content (usually about 8%). One of the effects is to make the boron in the soil unavailable to the plant, as well as contributing to scab in susceptible varieties.
I still go for boron deficiency symptoms. This does not necessarily mean that your soil is deficient in boron, merely that you may have made it unavailable. Boron is also not very soluble, and the effect of the summer drought would have been to exascerbate any calcium induced deficiency.
I won't add pelleted chicken manure next year then! What sort of fertilizer do potatoes grow well with? How about the potato fertilizers by Thompson and Morgan or Organic Gardening Catalogue?
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I have an old D.G. Hessayon "Vegetable Doctor" book (1978), and it has a similar illustration to your photo. I quote "Spraing. Tubers are normal on the surface; discoloured inside. There are several causes - viruses, trace element deficiency and water shortage." Hope this helps and not cause confusion.
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I won't add pelleted chicken manure next year then! What sort of fertilizer do potatoes grow well with? How about the potato fertilizers by Thompson and Morgan or Organic Gardening Catalogue?
If you can loads of horse manure that should be enough - it is all I use on spuds
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And failing that, plenty of good old fashioned garden compost (well rotted of course). The only additional fertilizer that I use is dried blood top dressing a couple of weeks before the tubers are expected to start forming, when potatoes always appreciate the extra nitrogen.
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I won't add pelleted chicken manure next year then! What sort of fertilizer do potatoes grow well with? How about the potato fertilizers by Thompson and Morgan or Organic Gardening Catalogue?
If you can loads of horse manure that should be enough - it is all I use on spuds
When is the best time to add manure for potatoes? January? and does it have to be weel rotted at this stage?
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Manure should always be well rotted before being dug in. Cow manure is best applied in the autumn. However, horse manure, being lighter and warmer, can be dug in in the late winter. Well rotted compost can be dug in at any time.
Fresh manure dug in for potatoes greatly increases the susceptibility to scab, and, of course, slugs absolutely love manure.
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I usually lay mine in late autumn when it arrives on the plots then it has plenty to time to settle down - I don't even dig it in, worms will do that and it just gets turned over when I plant the spuds
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Fresh manure dug in for potatoes greatly increases the susceptibility to scab, and, of course, slugs absolutely love manure.
interesting - I have found the exact opposite, virtually no slug damage at all on my spuds
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I did say `fresh`, Calendula, and I should have added `cow`. I`ve never had any trouble with rotted horse manure either, but on the two occasions when I had to use fairly fresh cow manure my potatoes were like colanders. You would in any case avoid the problem by leaving the manure on the surface for the worms to work in, whereas digging it in frequently results in buried lumps (particularly with only half rotted stuff) which are an absolute magnet for slugs.
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Since my last posting on this subject I now find that I have to throw a very large spanner in the works by advancing a hitherto undiscussed theory. This is as a result of a suggestion, made to me by someone with far greater knowledge than mine, that I should consider Internal Heat Necrosis as a possible cause. I had never heard of Internal Heat Necrosis before then, neither (apparently) has it come to the notice of the RHS or HDRA, and there do not appear to have been any recorded cases in Britain.
Inner Heat Necrosis is a purely physiological disorder of the tuber which causes damage similar to that shown in Rhys`s picture, and is a disorder well known in countries where summer temperatures are somewhat higher than we are normally accustomed to.
The disorder is caused by a period of high temperatures during the period between tuber initiation and harvesting of the plant, usually in conjunction with dryness of the soil resulting from such temperatures. Analysis of tubers so affected usually indicates a low calcium concentration in the tuber, the perception being that the effect of the high temperature and the dry soil together is to restrict the ability of the plant to take up the necessary amount of calcium even though it is present in the soil. The disorder is further exacerbated by harvesting during high temperatures.
Rhys`s potatoes (Maris Peer), as second earlies would indeed have spent at least part of the tuber growing stage in the very hot weather, and she has confirmed that she harvested them also in the hot weather.
It is impossible to say definitely that IHN was the cause of the damage in this case, or to rule out my earlier suggestion of induced boron deficiency, but after considerable research among transatlantic websites I now consider IHN to be the more likely cause.
The disorder is purely physiological, and so cannot be spread from plant to plant or persist in any way in the soil, and is only likely to appear with the sort of weather conditions (heatwave and drought combined) that we experienced this summer. However, this may well be yet another instance of the effects of climate change, and one which potato growers should take note of for the future.
Resistance to the disorder varies with different varieties of potato – research in the USA indicates that immune or resistant varieties have higher tuber concentrations of magnesium, sulphur, manganese and calcium, and lower levels of potassium. Unfortunately we do not have the US varieties in this country, and no research appears to have been done yet on our own varieties in this respect.