Poor yield of potatoes and black dots on tubers.

[Mark_Riga]

I grew rocket and vivaldi on a patch of ground and both had very reduced yield this year and also the tubers were small and had black dots on them. The poor yield could be due to the dry weather though they were watered on occasion. Can anyone identify this? pictured is some of the vivaldi. I think it means I don't grow spuds there for maybe 4 or 5 years.



It was like they had blackheads 1 to 3mm. deep.

[Mr Bones]

Could be just small concentrated areas of scab which is probably the result of dry conditions.

[Thelma Sanders]

I've had the same and I also think it's just something to do with the dry weather, as I've never seen it before this year. I'll not worry about it anyway

[bario1]

Mine were so bad I didn't bother eating them, covered in ugly warts!

[lottie dolly]

I would just peel them before use,in all honesty,it could just be the skins,if so,and you not want to store them,prep them for the freezer,chips,mash,skinless wedges sprinkled with a flavour part cook them,they are fine,

[WeeGarden]

Mine were like this too and I put it down to dry weather. The scabs come off and the potatoes are fine underneath.

[Thelma Sanders]

I just made a huge stir-fry pan of dryish mixed veg curry, including the worst of the potatoes, skinned and quartered. Had some for tea and I'll be freezing the rest in portions

[It never rains..it pours]

My earlies that are just finishing as cropped well are similar. Quick rub off with knife and they come up lovely. Looks are only skin deep, supermarket ones may be pure white but sprayed with lots of chemicals over the season and when in store

[Mark_Riga]

Well thanks for the replies - it seems to me there are probably more diseased seed potatoes out there than there should be. I know what scab looks like and it doesn't really affect the yield at all but this seemed a bit different. The black dots seemed like what are known in the trade as sclerotia and it looks like what is described in the link below but unfortunately I didn't examine the stems and roots so can't be sure. Seems like may be related to scab though as people say. Peeling the tubers though leaves very little left. They did last till my maincrop grown in a different area were ready and the yield of these was very good, though affected by scab. These were mainly Carolus which I would recommend as good to cook and immune to blight.

Black Dot Disease of Potatoes fact sheet