Have I got potato blight?

[grubbyhobbit]

Help!
Just lost another potato plant.
Second one - both on ends of rows, although not the same row.
Symptoms are that the plant just withers and dies, when pulled up the base of the stem is rotten and when dug up the seed potato on the bottom is also rotten and stinky!

I dug the last one out of the soil, and the plant next to it seems to be fine.

I've checked the symptoms of potato blight, and all the books say that brown spots appear on the leaves, but I've seen no sign of this.

What is this and what can I do to stop it?

[grubbyhobbit]

[Merry Tiller]

No, it's not blight, probably blackleg or some other kind of rot.
This often happens to mine where the ground stays damper in the spring, usually a plant at the end of a row

[kenkew]

What do the leaves of the affected plant look like, colour especially? Are there ANY tubers at the base? Is there signs of grub attack on leaves or tubers? My first guess is blackleg.

[philcooper]

The good news is - you don't have blight

It doesn't sound 100% like blackleg either:

"This bacterial disease, caused by Erwinia carotovora, causes some plants to die before they emerge, resulting in missing plants in the row. Plants that do emerge may be stunted, have bronzed leaves, and finally wilt and die. The base of affected plants will have a shiny wet black rot extending from under ground up the stem several inches above the soil line. This symptom, the "blackleg," is diagnostic. The seed tuber may rot from Fusarium dry rot or bacterial soft rot, both of which may provide plant stress that triggers blackleg development. Blackleg may also occur on upper parts of the stem, a condition called aerial blackleg, when overhead watering is used.
Blackleg bacteria are present in almost all tubers, including seed, but generally do not cause disease unless weather conditions are favorable. Cool, wet weather at planting favors both decay of the seed piece and blackleg. Blackleg is favored by wounding during cultivation, wounding from insect feeding and fertilizer burn".


So some other bacterial rot

Phil

[grubbyhobbit]

Answers to questions asked...
Most of my spud plants have slight white mottling on the leaves, but are strong
and healthy otherwise.

They have all been slightly nibbled, as I'm trying to be as organic as possible.

Not seen any signs of bronzing, the plants just seem to wither.

No tubers on the bottom of either of the plants, just the rotted seed potato that they came from.

[/list]Any tips for blackleg control?

[philcooper]

Blackleg tends to come with the seed tubers so buy certified seed - but even that doesn't give a 100% guarantee

There is no cure but it is made worse by planting in cold wet conditions (ie UK in March, April and even May!)

Phil

[Svea]

i had one plant the same, and also two plants that failed to emerge completely.

dug up the diseased plant and a handful of tiny potato crop from it, also a rotting seed potato. found another rotten seed potato from one of the 'missing' plants. but the third one remains missing. who knows what happened to that?!

i now have a wilting potato plant which looks like a fox has walked right through it and bent/broke the stems. i will probably ldig this one up first to see what's what.

svea

[aquilegia]

I have a few suspicious looking plants - a few have browned leaves at the tips. They have definitely suffered from the heat over the weekend, even with daily watering (it's hard to keep them moist in pots when the garden's that hot). They are also suffering slug-attacks. Do you think the heat might've browned the leaves or might it be blight already?

But on a brighter note - my Charlotte and Anyas in the ground are flowering!

[redimp]

I dug up a couple of plants that were looking sickly at the weekend - similar symptoms to those described - I did have some potatoes - most were small but one or two larger ones, and they did still taste delicious - my first ever potato crop   :D  My ill looking plants are mixed in with the healthy ones too - was trying to work out whether they were the ones under the fleece borders during the frosty weather and that maybe the frost got them a bit.

[Kevins299]

it seems like black leg. we have many with similar symptoms on our allotment in Roehampton. dig up and dispose of preferably by burning. I have grown mine in a tub and so far so good.

[tilts]

I too have a couple of potatoes like this and have seen it amongst others on the site.  I have checked some reference books after thinking that it might be blight, todate have found info regarding magnesium deficiency which seems to answer the wilt and pale colour of my spuds ~ I haven't dug one up yet, should i try?

[philcooper]

Tilts,

Given the very dry hot weather at the moment, pale flagging leaves could just be shortage of water. A foliar spray of a fertiliser containing seaweed or Maxicrop Tomato will quickly help if a nutrient deficiency is the cause.

To check for black leg just clear the soil around the stems and look for a black leg (hence the name) The picture above may help.

There have been only very few outbreaks of blight so far this year - next month is when then normally really start.

Leaf blight (known as late blight in the USA) symptoms are:

Blight may appear on leaves, stems, and tubers. Leaf symptoms appear as pale green water soaked lesions. These lesions are usually at the tips or margins of the leaves, but not always. The lesions grow into brown or purplish-black lesions which sometimes have a yellow halo. The halo is not always present in late blight infections. During humid conditions a white growth of mycelium and spores can be seen on the underside of the leaves. Lesions also appear on the petioles and stems as black, greasy areas.



Ideal conditions for leaf blight are a minimum temp of 10 degrees C and a humidity of 90% for 48 hours (known as a Smith Period), but any period of high humidity and reasonable temps will help blight develop. Unfortunately the symptoms take 4 - 5 days to appear after infection so the only safeguard is to apply a measure before you see the symptoms. Bordeaux mixture or Murphy's Copper Fungicide puts a protective layer of copper sulphate on the leaves and stems, the good news is that it doesn't enter the plants' system (unlike systemic fungicides) so can't get into the tubers,  the bad news is that it washes off so needs replacing every 2 weeks. So when you hear a blight warning - get out and spray.

You can find blight warnings at http://www.potato.org.uk/blight05.asp?sec=1019&con=2110&lcon=2166 - with other useful advice

For more info on blight see http://biology.bangor.ac.uk/~bss081/blight_beginners.html

Phil

Now be afraid!!!  ;)

[Yuet_Lee]

I have one witling potato plant aswell was grow in the big tub. These hasn't flower yet :( Is that potato blight ???I have no idea why the plant were going yellow. All other plant were still going strongly.One or two just started to flower ;)please help!    yuet

[philcooper]

You don't say what variety(ies) you are growing - first early may well start dying back naturally at this time of year especially if planted out early or in containers in a warm spot and I can't see enough of the leaf detail to see whether you have the classic round brown patches.

All sorts of things (non-disease related) happen to potatoes when we have a spell of very hot dry weather, especially those in containers where the soil temp gets a little high for the poor little things

There is also a thread on the same subject at http://www.allotments4all.co.uk/yabbse/index.php/topic,10014.0.html

[tim]

Poor Yuet!

[aquilegia]

Some of mine are looking like Yuet's too. I'll try moving them to a more shady part of the garden, but there isn't much of that at the moment!

[westsussexlottie]

My first earlies all looking like Yuets too and they are in the allotment not a tub! It is the high heat levels which they don't like I'm sure. I feel the same.
The second earlies and maincrops looked fine (yesterday)... don't want to speak too soon!

[redimp]

Some of my first earlies - Rockets, are starting to go that way and they are in the allotment.  Have an explore with your fingers Yuet to see what is in there.

[Yuet_Lee]

I have dug up some potatos from the tub. It had got quite a few in with no sign of infection,lucky me :)because I'm not expected many in!