Topic: What is eating my potatoes?

[worldor]

We have planted three different types of second early potatoes. The carlingford seem to be disappearing from underneath. I have dug down and nothing. Not even the original seed potatoe. The others higher up the plot seem to be thriving. We have 21 left out of 33 and I am concerned we will lose the lot. Any ideas?

[calendula]

blimey  :o I don't think I have ever heard of a whole or part of a crop disappearing without a trace but one of my books suggests 'gapping' which is when there are no sproutings due to either frost or diseased tubers - maybe change your supplier - did you actually get any haulms though, i.e. something green grew

[worldor]

Yes we did get lovely green growth and in some cases the green disappeared in others it was just there attached to nothing. No surface disturbance at all. I suspected slugs working underground and have been dreaming about them munching their way through all my crop.

[saddad]

Slugs never finish off a tuber totally IMHO... is the bottom part subject to waterlogging? If you only had small tubers because of the dry summer and hadn't taken them out they may have rotted in the recent damp... but very unlikely!
 :(

[calendula]

it is a puzzle  ??? are you sure no-one has actually pinched them, it is the only thing I can think of where they might have totally disappeared

[worldor]

I hope no one has pinched them. The ground doesnt look disturbed but I suppose a two legged theif could have tidied up after them. Don't want to think that could be true.

[Robert_Brenchley]

Even if they did, I'd expect to find a few accidentals. The soil would be loose after they'd gone through it as well.

[calendula]

truth is stranger than fiction  :)

[Kepouros]

I dug up my second early Nadines this morning, and I found a couple of plants like yours, with absolutely nothing on them.  All of the plants had full foliage until they died down a fortnight or so ago, all had flowered and most had borne seed pods.

Having noted this thread yesterday I washed the roots off carefully so that I could examine them.  I found that there were no stolons at all, and hence no tubers.  It is the stolons from the bases of the stems and buried leaf axils on which the tubers form, and they are quite different from the normal fibrous roots of the plant which were quite normal.  I thought at first that the stolons might simply have been eaten by some underground pest, but there was absolutely no sign that any had formed. 

I have a dry gravel soil, and throughout most of July (when the stolons would have been growing) and early August the plants wilted badly in the heat.  I can only assume that as a result of the stress so caused tuberisation had completely failed and the plants had diverted sych energies as they had into seed production instead.   Sounds far fetched, I know, but extreme stress can cause plants to do very strange things.

[worldor]

My problem isn't the same as yours then. We have only recently planted these second earlies, carlingford, 21 of the plants are thriving and some even have flowers forming but 12 of the plants and tubers have completely disappeared. There is nothing there. I have dug down to find the tuber to see if perhaps it had rotted or been got at by slugs but there is no sign that there was ever a plant there.

[Kepouros]

Sorry, I misunderstood.  I thought you were talking about plants with healthy foliage yielding nothing.

I would suggest that the cause of the problem is probably Fusarium dry rot affecting the seed tuber.  One of the symptoms of Fusarium in a crop is `missing` and stunted haulm which dies back.  Unlike in the normal rotting of a seed tuber, those affected by Fusarium rot much more quickly and the actual rotting attracts numerous soil inhabitants which complete the job of onsuming the remains.

Fusarium is normally only present in seed tubers that have been grown on contaminated soil and/or have been damaged in harvesting.  I obviously cannot state this to be the certain cause - I don`t think anyone could from what you say - but I would be inclined to think carefully about my future choice of seed supplier.
It is also a wise course to check all seed tubers most carefully for any signs of damage, however slight, or with any signs of skin lesions and reject any that show these.

[worldor]

They were bought from Alan Romans and looked in perfect condition on planting.

[worldor]

I am now finding evidence of blight on all three varieties of potatoes. We are cutting off any diseased foliage as advised on here. Is there anything else we can do?

[Kepouros]

Not really.  Once you have found blight the probability is that some spores will already have been spread to fresh foliage even though there are no visible signs. Spraying may slow the spread down a bit but won`t do anything about the disease actually in the plant.   As long as the attack does not spread too quickly you can keep picking off the affected foliage and try to keep the plants going for another week or two, but as soon as 30% of the foliage is affected you need to cut them down to ground level.
If you see any signs of blight attack on the stems (usually in the leaf axils) cut them down immediately.   It is important to remove every little bit of debris immediately after cutting down.  Although blight spores can wash down through the soil in wet weather, the main danger to the tubers is contact with spores on the surface when you lift them.  The spores take about 14 days or so to die off in the absence of a live host, so unless you can sterilise the surface with a flame gun you need to leave the tubers in for at least 14 days before you dig them.