We've recently moved to a new house which has a lemon tree in the backyard in dire need of some TLC -- but we're not quite sure what exactly is wrong with it. Two primary problems, which may or may not be related:

1) Lemons are covered to varying degrees in narrow black-brown scabby spots that come off when scraped. Sizewise they look kind of like insects, but there's no obvious infestation of anything living. The inside of the fruit is fine, and this seems to primarily affect the side of the fruit that doesn't get direct sunlight.

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2) The leaves have yellow-brown spots, and in bad cases are dried-up and crinkly.

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We're in Sydney, Australia, which is warm and fairly humid, but neither of these seems to match up very well with the descriptions here. Melanose, perhaps, but doesn't look quite the same...?

  • 3
    That clearly looks like an infestation of some sort. More like Lepidosaphes beckii. You can also check here. I don't know much about how to treat these insects :(
    – 4-K
    Commented Sep 5, 2016 at 15:02
  • Yes, some type of scale insect. A hand lens might help with identification. Commented Jan 1, 2017 at 2:34

1 Answer 1


Lemon Scab

management of Lemon Scab

You'll see a picture of your lemon 5 or 7 rows down on the images. The only way to control this is a copper spray. How big is your lemon? I'd check out a professional as this is a very big problem in your country and other MOIST environments for citrus. It is a fungus and to control MOST fungus one needs to put a little 'raincoat' on your plant. Water splashing up from the soil which is full of these spores is how this fungus infects plant material. There is nothing you can do after infection. This spray, is the little raincoat, and can get this disease under control by protecting splash (full of spores) from landing on the epidermis of your plant. Have you contacted your 'Cooperative Extension Service' of your nearby University? Don't know what they'd call it DOWN there, grins. They will love that you are aware! They'll have the facts for your area in Australia. Please tell us what they say!

  • Bingo -- but your results indicate it's actually Lemon Mussel Scale (Lepidosaphes beckii): thecitrusguy.blogspot.com.au/2012/05/… Commented Jan 9, 2017 at 3:08
  • @jpatokal I'll go look this up, isn't lemon scab sort of a generic label for similar diseases? The citrus guy? I shall keep your web site! Thank you!
    – stormy
    Commented Jan 9, 2017 at 23:37

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