Unhappy citrus plants - yellow spots on leaves


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Hello, new member here and this is my first post so hope I’m doing it right!

Around 3 years ago I planted some yuzu seeds and to my surprise they all germinated. I now have 15 plants ranging in height between 70 and 100cm. Over the last couple of months I’ve noticed small yellow spots on some leaves, which spread and then the leaf drops (4th pic). More recently new growth seems to have crinkly, curled, and sometimes yellow or misshaped leaves that have brown areas of discolouration (first 3 pictures) .

They are planted in citrus compost and have been fed weekly with citrus focus fertiliser. I don’t see any obvious pests on the leaves but there are sciarid flies in the compost, which I’m managing with nematodes and yellow sticky traps. I’m also trying to let the compost dry out a little between waterings to reduce the number of larvae in the compost. The plants get direct sunlight for part of the day.

I’ve also noticed yellow spots on new growth on a calamondin orange (final pic) that is a few metres away from the yuzus

Looking online there seem to be lots of reasons for yellow leaves - I really don’t want to lose these plants and would be grateful for any advice.

Thanks.
 

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What is the nutrient analysis of the fertilizer? Any micronutrients? If so, which ones? What are the label instructions for frequency and dosage? The yellow spots look like a micronutrient deficiency. If the potting soil is mostly organic matter (they usually are) it tends to mess with the availability of certain elements. A pH test will help narrow the possibilities.
The browning and distortion of the leaves are diagnostic for thrips and aphids-- look very closely at the undersides of the leaves for them. I don't see aphids so look for thrips -- they're small, light colored, move fast and hop.
 

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Thanks for the comprehensive response cpp gardener. The compost is called Citrus Focus and the fertiliser is from the same company. I’ve attached a picture showing the micronutrient content and I’ve been using the fertiliser with every watering over the last few months.

I’ve has a good look for aphids and thrips on the underside of the leaves but couldn’t see anything. I’ll keep an eye out for them now. There are certainly lots of sciarid flies/fungus gnats that seem to be resistant to the nematodes I‘ve been using. Have now moved on to predatory mites to see if they help
 

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IMO the problem are citrus mites. There are many types of them and all do the damage shown. They are very very tiny and one needs a magnifying glass to see them
 

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IMO the problem are citrus mites. There are many types of them and all do the damage shown. They are very very tiny and one needs a magnifying glass to see them
Thanks Chuck, and thank you for the welcome Tetters :)

I think you’re probably correct - the pattern of damage fits with some sort of mite. I’m not keen on using any pesticides - are there any natural predators that could help? I’m using hypoaspis with good results on the sciarid fly larvae and wonder if there’s anything similar for the mites.
 
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Thanks Chuck, and thank you for the welcome Tetters :)

I think you’re probably correct - the pattern of damage fits with some sort of mite. I’m not keen on using any pesticides - are there any natural predators that could help? I’m using hypoaspis with good results on the sciarid fly larvae and wonder if there’s anything similar for the mites.
Predatory mites are sometimes effective against other mites. I too do not like to use chemicals on anything but products such as Neem Oil and spinosad are not chemicals IMO. They are a natural substance, Neem from the Neem tree and spinosad is derived from a soil bacteria and distilled. Both are totally harmless and very effective
 

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Does Neem also harm beneficial predators like sciarid nematodes and the hypoaspis mites?
 
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Does Neem also harm beneficial predators like sciarid nematodes and the hypoaspis mites?
Not really. The nematodes and the hypoaspis miles mites live in the soil. If you sprayed the neem on the soil it would probably kill any nematode or mite that was on the surface of the soil but both of them live in the soil or underneath the surface of the soil. Just cover up the soil with a tarp or something and spray. If you want to get rid of the fungus knats just make a soil drench out of Neem Oil and soak the soil. It will kill any eggs or larvae present.
 

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