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Whats wrong with my discoloured brown lemons?

My established lemon tree which was at the house when bought it produces an abundance of fruit. They have small brown marks on the skin which last year did not seem to be a problem with the lemons being large and juicy. This year many of the lemons are discoloured brown in the centre or around the edge when cut in half, but are still juicy and not dry. Is this a disease or caused by insects and what can I do to prevent this happening next year?

Thanks

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JacobZ

Hi @frannie,

Thank you for your question and welcome to the Bunnings Workshop community, it is fantastic to have you with us.

It looks like you might have a case of lemon scab which is a fungal disease that affects the fruit, leaves, and twigs of citrus trees, including lemons, and is more common in humid or wet environments.

Do you have any photos of the tree that you could upload?

There may be some signs on the tree that would help to confirm this diagnosis. The fungus can cause small, scabby lesions on leaves and twigs, though the fruit is usually the most affected part.

To manage lemon scab, prune the tree to improve air circulation and reduce humidity. Apply copper-based fungicides, such as Yates Liquid Copper Fungicide during key growth periods, such as after flowering and during fruit set. Additionally, remove infected material, like heavily affected leaves or fruit, to limit the spread of the disease.

Preventing moisture buildup is crucial, along with regular fungicide treatments in areas prone to scab.

Allow me to tag @Noelle, our resident garden guru to see if she has any thoughts.

Let me know if you have any further questions.

Jacob

Noelle

Hi @frannie

The outside of the fruits looks very like lemon scab. However, this does not usually cause browning to the inside of the fruit. Affected fruits are usually OK for juicing but not for zesting or making marmalade where the skin should be perfect!.

The browning inside is often seen on fruits that are over-ripe and are starting to rot on the tree. This can also sometimes be caused by excessive rainfall and humidity as the fruits are maturing. Fruits that are brown inside should be discarded as they are likely to have quite an unpleasant after-taste.

The fungicide treatment outlined by Jacob will aid in the control of lemon scab but sadly won't save the current crop from the warty-looking skin lesions.

Sybille

https://www.workshop.bunnings.com.au/discussion/comment/41901#Comment_41901

I also have this problem with a very old lemon tree. Is it the same diagnosis or something else? Any advice for treatment would be gratefully received!!

JacobZ

https://www.workshop.bunnings.com.au/discussion/comment/86625#Comment_86625

Hi @Sybille,

A warm welcome to the Bunnings Workshop community, it is fantastic to have you with us.

It doesn't look like a fungal scab as it is a discolouration of the skin rather than raised sections.

I would say it is more likely related to a nutrient deficiency. I note that the leaves are slightly yellowing and there is some leaf curl, which can also be indicative of nutrient deficiency.

If you could get a wider shot of the tree and some photos of the yellowing leaves, this would certainly help us narrow down the issue.

I suspect the best course of action at this point is to apply a citrus-specific fertiliser such as Scotts Osmocote Citrus and Fruit Controlled Release Fertiliser to the base of the tree. This will give the tree the nutrients it needs to thrive moving forward.

Allow me to tag @Noelle to see what she thinks.

Jacob

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