Mystery potato pest

[Birdie Wife]

I've tried searching all over the web, including the RHS site, and I can't find out what's happening to my tatties. I think it's a pest rather than a disease because a few plants are affected, and the plants growing right next to them are fine. Also, I bought seed tatties so certified virus free.

These are the symptoms - leaves and stems going yellow and stunted, but not curling or going brittle. Tubers when I dug them up - slightly reduced yield but main symptom is ugly raised light brown lumps (not powdery or flaky) which appear superficial, ie. I can rub the surface of the spot off and the flesh underneath is still white. Sometimes these spots cover more than 50% of the tuber.

My thoughts are some weird kind of scab, or another possibility is leatherjackets - but I don't know if they can inflict that kind of damage. Although it's superficial, the affected tubers are not very appetising and I'd rather get to the bottom of the problem and sort it if possible.

Can anyone help?

[SueA]

Hi Birdie, does sound like some kind of scab but not sure which, you can get common scab in dry weather & sandy soils or powdery scab in heavy soils & wet weather so it depends on the ground conditions you've got & some varieties are more susceptible than others. If it just looks like scab though the potatoes should be O.K. to eat if you peel them. Hope someone else has a better idea!

[JennieAtkinson]

I'm having a similar problem too. I meant to take a photograph last night of the ones I dug up as I was wanting to ask for advice. As you say BW the scabby bit does rub off and we ate the potatoes last night (I feel fine today - well normal anyway!).

I seem to remember I had similar problems last year. My plants look very healthy though. What sort are your growing? I've only dug up two of the Charlottes so far and only a few tubers are affected. Some were completely clear.

Interested to know what others think.

[Birdie Wife]

I'm growing Red Duke of York and Rooster. Haven't lifted any of the Rooster yet but some of the stems and leaves look affected by the same thing. My soil isn't sandy or heavy, just a nice in between! I had scab on my tatties last year but it didn't result in the raised bumpy bits that I had this year. I'll try and get a photo, that'll probably help...

[JennieAtkinson]

Remembered last night that one of my MOM prizes was the pest detective. So fire it up and I must say it is very good. Loads of pictures of problems with potatoes, but not what I'm getting! It doesn't look like ordinary scab. I'll try and get a picture tonight, need to dig some up for tea.

[sewer rat]

Bw
Sounds like common scab to me - common scab produces raised lumps, and powdery scab produces sunken depressions. If you get a photo, then that'll help more.

[nick the grief]

Rat you've certaily changed since you got married, you look like a girly now

[sewer rat]

Nick
You certainly haven't changed - that is of course my now very grown up 5 year old, Iona - professional pea sheller.

[JennieAtkinson]

A photo of my "scab". What do you think? Sorry it is not a very clear photo.

[SueA]

Think we're probably all just a bit 'scabby' Jennie! I harvested my 'Harlequin' potatoes from the barrel last night & a couple of them had a few spots of scab on (see pic. attached) It's probably due to the weather being so hot, maybe we think we've watered them enough but they have been drying out too much in between especially as it's been quite windy at times too.

[Bugeyes]

Yep my Rocket spuds just harvested look disgusting with the amount of scab they are carrying but taste delicious when cooked! You two have nothing to worry about.....

[Birdie Wife]

That's reassuring, thanks everyone for your excellent advice, as usual. I think it must be scab, but some of the tubers are so badly affected that they've warped into some potato version of the elephant man!! Thankfully most only have one or two spots on them. I lifted a few more yesterday and found a millipede with it's head buried in the top of one of them too, he was most put out when I picked him out of the spud and sent him on his way. Sorry little critter.

[JennieAtkinson]

Thanks for your reassurance - I had hoped it wasn't anything too serious, especially as we had been eating them

Dug some more up from the middle of the row last night and they are quite clean, so perhaps it was just the ones on the end drying out.

Something I keep forgetting to do is pile up the earth around the next plant waiting to be dug up. Forgot the other night and left a couple to grow green. Could kick myself for not thinking of that