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Weird spots - potatoes

This is a new one on me. I have potatoes in buckets on spent compost. This has bed done before with no problems but they have been slow and not grown as much as I would have hoped. But more importantly they have developed tiny spots( like rust spots). Any ideas, should I feed them with Tom feed?? 

this isn't blight as the plants are healthy another than the newly formed spots. 


  • I've had this problem before, a bit like scabs on the surface?  It hasn't affected the growth, or the eating, as long as you cut them off before cooking. I think it can be something to do with the lack of nutrients in the compost, however I've used fresh compost and still got it - as long as the plants are healthy, I wouldn't worry image

  • This is just on the leaves so no idea what's happening under the compost. Should I feed with tomato feed?? Thanks for reply

  • marshmellomarshmello Posts: 683

    If its scab - which is common on potatoes, there is common and powdery scab. One is bacterial, the other fungal.

    • Common scab - caused by lack of water
    • Powdery scab - caused by wet conditions

    Further reading -

  • marshmellomarshmello Posts: 683

    Oh, on the leaves.

    How you followed crop rotation ?

  • They are in bucketso with spent bedfing flower compost. So shouldn't have any issues with rotation. 

  • marshmellomarshmello Posts: 683

    Never had this effect my potatoes before, but I've had it effect my leeks, onions and garlic etc, mid to late summer...

    ...but having done a bit of research, come across common rust Puccinia pittieriana or deforming rust Aecidium cantense as a possible answer.

    Google images for each and see if it matches. 

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