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Strange marks on dahlia leaves

These have been on my Bishop of Leicester all Summer but they're even more widespread now.

Haven't really noticed it on any of my other dahlias. Any idea what's causing it?


  • fidgetbonesfidgetbones Derbyshire but with a Nottinghamshire postcode. Posts: 16,462
    I think it has leaf miners.  They burrow through the leaf eating the centre out.
  • Dirty HarryDirty Harry Posts: 1,021
    edited September 2019
    Would it be odd to only be on one plant? (as far as I can see anyway)

    There are 4 other dahlias in close proximity to this, all in pots.

    When I google for leaf miners the damage looks like the trail a snail/slug would leave yet this is nothing like it.
  • BobTheGardenerBobTheGardener Leicestershire, UKPosts: 11,391
    edited September 2019
    The pattern suggests some sort of necrotic spot disease, possibly caused by a virus (eg a mosaic virus) or bacteria, but I don't know exactly what.  Safest would be to destroy the plant in case it is infectious via thrips or aphids etc.
    A trowel in the hand is worth a thousand lost under a bush.
  • Sounds extreme!

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