How to treat citrus tree spots?

[Will01]

 Is anyone able to please diagnose and recommend how I treat these black and brown spots on my dwarf lemon tree? Many thanks in advance!

[MitchellMc · Accepted solution]

Hi @Will01,

They appear to be hard-scale insects, so you might like to check out this article: How to get rid of scale insects. The mainstay of scale insect control is the application of horticultural oils. Oil sprays suffocate small insects such as scale Insects. I'd recommend you apply Multicrop 1L EcoPest Oil Insect Spray. As this is a hard scale, the spray won't remove the scale that is already on the fruit, but with continued use, it should help prevent future fruit from having the same issue. By the way, as long as the plant is healthy, this hard scale is really an aesthetic issue, and the fruit will be perfectly edible.

Let me tag a couple of our resident gardening experts, @Noelle and @mich1972, to get their thoughts.

Please let me know if you have any questions.

Mitchell

[Will01]

Brilliant- thank you very much!

[Noelle]

Hi @Will01 

Mitchell is definitely correct in both his diagnosis and recommended treatment!

[John57]

Hi Mitch 

Is this the same problem, of scale insects?

Limes in this case.

 

[JacobZ]

Hi @John57,

No, that does not appear to be because of scale insects. You would expect to see smaller spots in much larger quantities if it was due to scale insects.

That looks like either the early stages of citrus brown rot, a fungal issue caused by Phytophthora, a soil-inhabiting species of fungi or sunburn.

If you press on the brown spots, do they feel soft, like the flesh beneath is rotting? Or do they still feel firm?

If they feel soft, then I'd say it is citrus brown rot, in which case I would suggest you need to remove the affected fruit and dispose of it, as it contains fungal pathogens that can spread to nearby fruit. 

If they still feel firm, then sunburn is a likely cause.

Allow me to tag our knowledgeable gardeners @Noelle and @mich1972 to see what they think.

If you can report back with answers to my above questions, we will be able to assist further.

Jacob

[mich1972]

@JacobZ  Certainly looks fungal and sunburn. Definitely remove from tree and straight into the bin not compost. Good luck @John57 🌿🙂

[John57]

Hi all

So the squeeze test shows it’s a little soft but could be explained by the thinner skin. It’s not mushy at all. These two surfaces are upward facing. I’ll take these two fruit off and cut them open later. Thanks for your help as always.

[Noelle]

Hi @John57 

If the fruits are not spongy under the brown areas, then I'd be fairly happy to diagnose sunburn as the most likely cause. Cut the fruits open and if they look OK inside, then that would be sufficient confirmation for me to say it's sun exposure. My own lime tree suffers from the same symptoms when we've had a hot spell and the fruits are still developing - they are quite all right inside and can be juiced without any issues.

[John57]

Hi Noelle

Here are the two limes. There is some flesh bruises but I have been squeezing the fruit so I can imagine this is the reason for the discoloration too.

 

 So my thoughts are it’s sunburn. It was upward facing. It’s the only limes affected on two trees.

So I’ve got two cut limes to juice.

Merry Christmas to you and the team at Bunnings Workshop 🎄🎅