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My Indian Guava (18 months) has been getting more and more rust looking spots on its leaves.

Front side: enter image description here enter image description here

Back side: enter image description here enter image description here enter image description here

  • Is this a nutrition issue? (They are given a weak fertiliser about once every 3 months)
  • A type of insect? (I couldn't find any active bugs, and they get sprayed about once a fortnight)
  • Too hot? (Days are around 36C)
  • Too cold? (Nights are around 5C, but it lives in a greenhouse)
  • Mould? (I mould spray every month)

I found this: What are these red spots on my guava leaves? but the pics they have seem very different to mine, so I thought it would be OK to ask separately.

I rescued this plant when it was a tiny little sapling about to be thrown out by my local hardware store (Bunnings Australia), so I've got quite an attachment to it and would really like to figure this out. I've tried so much without effect, so I'm happy to take whatever steps people recommend to get it back to health!

Thanks in advance!

  • Any chance of a photo of the back of the leaf? If spots become yellow then big problem. – Polypipe Wrangler Jul 18 at 5:19
  • @PolypipeWrangler: I really hope that you're wrong. Myrtle Rust (from what I've read since you posted) seems to be devastating, contagious, and very likely would require the destruction of the plant itself... not to mention a reporting obligation to the Qld Dep. of Ag. (I'm qld based). I've edited the question to include back side shots, they look the same as the front and I've kept a very close eye on the plant and have never seen anything like the yellow spore clusters that seem common to this fungus. Your help so far, and any further help is greatly appreciated! – Shane Gadsby Jul 18 at 11:30
  • You can send the photos in to get it identified at: daf.qld.gov.au/business-priorities/biosecurity/… The spores may stay brown either because they are winter spores (under 15 C) or on Guava (haven't found out yet). – Polypipe Wrangler Jul 19 at 0:54
  • I've submitted to the linked Qld government website and will see what they say, but I'm already preparing myself for a positive identification... I'll update here as soon as I receive a response (or withing a few weeks regardless) – Shane Gadsby Jul 20 at 8:22
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It is disease.

What is important to know here (Australia) is whether this is puccinia psidii (Myrtle Rust) because the nursery will have to be informed.

official info at https://www.environment.gov.au/biodiversity/invasive-species/diseases-fungi-and-parasites/myrtle-rust Contact details for help in Victoria at: https://agriculture.vic.gov.au/biosecurity/plant-diseases/shrub-and-tree-diseases/myrtle-rust/treating-myrtle-rust-in-home-gardens

This is Myrtle Rust on Psidium spp.

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