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Recently I noticed my green grapes leaves don't look too good. There's nothing like scales or ants or any other sign of parasites. Only older leaves are affected, new ones are fine as you can see on the photos.

Do I need to give it more water? Add some fertiliser? Or is it just normal?

older leaves

newer leaves

I'm in Sydney, Australia. It's end of summer here now.

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Bacterial leaf spot infection. There is no cure, but you can try to avoid it next season. Here are some tips:

Cultural:

  • Clean up and burn/landfill fallen leaves/fruit. Don't compost.
  • Loosen the soil around the base of the plant. Add 1" of rich compost to the soil.
  • Mulch well with an organic mulch to help conserve moisture
  • Water whenever the ground is dry more than 1" down. When you do, water deeply.
  • Fertilize regularly while the plant is growing. Any balanced general fertilizer will do.
  • Avoid letting rainwater splash up from the ground onto the leaves - provide ample support.
  • Sterilize all pruning equipment before use.
  • When the plant gets crowded, thin it out to improve air circulation.

All of this helps prevent the disease, by limiting contact, and by building up the plant's conditions. A healthy plant easily wards off disease.

Here is some useful further information on the disease:

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