How to treat my diseased lemon tree?

[KevinPlant]

It looks like some pests bite the leaves.

And also it never fruits.

Can someone take a look and give some suggestions for my lemon tree?

[BradN]

Hi @KevinPlant , and a very warm welcome to the Bunnings Workshop community. 

I don't know what's eating the leaves in those top pictures. Could you take a closer look at the plant and see if there are any caterpillars, grasshoppers or other herbivorous insects hiding under the leaves or on the stems of the plant? 

The damage to the leaves in the bottom photo is caused by leaf miners. These are insect larvae that live inside the leaves. You will probably want to treat them with eco-oil. 

Let me share horticultural expert Adam_W's advice from this thread: 

"They're a tiny grub that burrows (or mines) between the leaf layers so normal insecticides won't work on them.
Best option is an oil-based spray but you need to cover leaf surfaces totally both top & bottom.
My personal fave is eco-oil.

Just read any precautions about spraying on hot days etc.
You should only need to spray the new foliage and repeat applications may be needed.
The damaged leaves won't repair so you'll need to prune them off for appearences sake.

Should just add... if you don't want to use any sprays, even safe ones, then you can prune off all new foliage however collect all leaves, seal them in a bag and place in the rubbish."

I'll also tag @Adam_W and another garden expert, @Noelle , to see if they have any more specific advice.

You can also see some more suggestions for leaf miners in this thread: What should you do about deformed citrus leaves?

Cheers,

Brad

[Adam_W]

Hi @KevinPlant 
Definitely some caterpillars doing damage there, that what the leaf holes are.
This silvery trails are, as spotted by @BradN, leaf miners and regular applications of eco-oil to top and bottom side of leaves will kill them. Note that the damage will not repair so you may want to trim those leaves off.

If the tree isn't fruiting there could be a heap of reasons.
Is it getting at least 5 to 6 hours of sun a day?

Is it being regularly feed with a balanced fertiliser?

[KevinPlant]

Thanks so much for the suggestion. @Adam_W 

• I will go to Bunnings to get the eco-oil, as suggested.
• No, I don't regularly feed my lemon tree with a balanced fertiliser; however, recently, I bought this product: Charlie Carp 2.2L All Purpose Hose On Liquid Fertiliser. Is this a good one for lemon trees? How often should I use this product to spray the leaves?

[KevinPlant]

Hi @BradN 
Thanks so much for your suggestion. I will try this product eco-oil.

[MitchellMc]

Hi @KevinPlant,

Charlie Carp 2.2L All Purpose Hose On Liquid Fertiliser, would be a good fertiliser to maintain your plant. However, if you haven't fed for a while, I'd recommend going with Scotts Osmocote 500g Citrus & Fruit Controlled Release Fertiliser. The Scotts product would be a fully balanced meal for a somewhat starving plant.

The Chalie carp is applied to the foliage and soil. If you are only using it, you would do so every 2-4 weeks during the growing season. Do not apply this full dose whilst also applying the Scotts product.

On a side note, your first picture has either a native bee or wasp on the leaf, and he's not the culprit. Please don't spray them with the Eco-oil. 😊

Mitchell