Potato Problems - Brown rotting on the stems

[Parsleythelion]

Afternoon All

With photos

I am growing some late potatoes for Christmas etc in potato bags. They were planted at the beginning of August and the plants are about two feet high from the top of the bag. I have been earthing up and moved them into my unheated greenhouse last week. The temparature hasn't dropped too low and we have not had any frost in the area.

I had a look at the plants yesterday and of the 4 bags growing, one of the bags had plants that had a brown mould growing on the stems and when I touched it it was squishy and the stems collapsed. The leaves were all fine (no blemishes). I removed all the offending plants (outside) and then decided to destroy them (hence no photos).

I have looked at other pages referring to blight and it doesn't seem to be that.

Any ideas?

[rustylady]

Too warm, too wet, and not enough air circulation. How big is your greenhouse?

[womble]

Not sure about the brown mould, but it sounds like black rot to me.

[OllieMartin]

Was the mould constricted to one side of the stem? Are the leaves discoloured or wilting? and is there any sign of damage to the tubers?

I would suggest, either fusarium wilt or verticillium wilt, both of which have very similar symptoms to what you describe.

Plenty of images here

[gojiberry]

Sounds like all the classic symptoms of blight to me.

Ian

[OllieMartin]

Never had blight myself, but I didn't think that you'd see a visible "mould" growing, but more of a browning.

[Parsleythelion]

Thanks All for your comments

Rustylady - my greenhouse is 6X8 and has an auto vent in the roof, the door has been closed so it might be getting a bit humid in there during the day. I left the door ajar today.

OllieMartin - I looked at your images and in some ways it look like the frost damage (even though we have had no frost in sunny SE London!!) but the damage to my stems didn't look like the images. i should have taken some snaps but was eager to get rid of the offending plants in case it spreads.

At the back of my mind I am in agreement with gojiberry and think it coould be blight, but I hope not.

I will keep an eye on my other plants.

[tattieman]

It could be possible that it was blight spores on the stem where you have been watering the plants? If blight was in the greenhouse I think it would have taken them all out.
Another possible problem may be blackleg when you say that the stem was squishy.
I will see if any other ideas pop into my head.

[Parsleythelion]

I think it is blight (photos)

Thanks tattieman but the plants my greenhouse are now infected I looked this morning and took these pictures (sorry for the quality, but the iPhone doesn't take good pictures close up and this is the only way I can transfer them at work).

From what have read it seems they are all lost and the only option is to burn them.

Does blight infect the soil? I have four potato bags full of compost, what can I do with that?

[jacob]

Looks like botrytis to me -- light brown/grey patches that go furry if left for a few days? Greenhouses get moldy old places in the autumn and even strong plants will succumb in the end. The spores will be in the air and dripping down with the condensation.

I'm afraid all you can do is chop of the affected leaves and keep your fingers crossed that there is some plant left.

This is why we clean our greenhouses before a new year's planting!?

[Parsleythelion]

Thanks Jacob

The plants are all pretty much infected so I will destroy all of them.

With regard the cleanliness of the greenhouse, this was only erected about 3 weeks ago and was brand new from the box!!! The spuds started off outside so I may have brought the spores in. Oh well, looks like my new greenhouse will need a good clean then!