What's wrong with my Japanese quince Toyonishiki?

Since it has all three colors I’m assuming it’s Toyonishiki.
Last year it suffered drought and sunburn, at least I thought it was sun burn. I removed the damaged leaves and moved it to a shady spot.
This past spring it flowered and the leaves looked healthy. However as the summer progressed the leaf damage returned and progressing.
I’m thinking it might be root nematodes.
should I repot it as soon as possible or wait to later in the Fall. And how should I treat the roots? What soil can I use. Any suggestion will be welcomed.
Thank you.

What is the reason that has led you to guessing its root nematodes or root related issues?

Quick reading I found:
Years with heavy rainfall may cause fungal leaf spot, which can cause defoliation. New growth can be affected by aphids. Occasionally, scale and mites may be an issue.

Not suggesting your in correct with the root related issues…

but could the “root cause” (pun intended but probably made it confusing)…aka main issue be a lack of balancing water and oxygen?

1 Like

If your weather is as crazy as mine has been the last three years…(eastern Wa.state)… The tree looks OK…
Organic fertilizer and micronutrients now, light fall pruning, winter sulfer spray (or whatever is currently used), spring consertive repot into bonsai soil…
Post next summer for us to follow!

Thank you for you replies.
The reason I think it might be root related is because I don’t see any other obvious reason. No aphids, scales, mites nor mildew. There was a heavy infestation of aphids last summer, I used Neem oil and it cleared up. This year all seemed well until late Spring/early Summer when the leaf tips started turning brown, and it has, slowly, continued to progress throughout the Summer.
Yes, we’ve had a prolonged cool and rainy Spring and Summer. The last 3 or 4 days have been the first consecutive days we’ve had with no rain. All this rain, wouldn’t it cause root rot or other problems?
Today I repotted a much smaller, younger JQ with similar leaf damage, and sure enough it had 2 woody knots. I used a mix of sifted pine bark and perlite. Didn’t use anything else and keeping my fingers crossed and hope for the best.
Ryan suggests to repot quince in the fall to reduce the chance of root nematodes. What do you think?

Hey Laura,
From what I can see, it’s root related. You’ve probably been keeping it a bit to wet.
Cut back a bit on watering and it should be fine.
As for fall repot, if you can keep it frost free there shouldn’t be any problems.

I decided to remove all the damaged leaves and this is what I have left.
I checked the soil and it does not look compacted and so I’m contemplating not repotting this fall, as you have suggested.
Now I would like focus on girth improvement. What should my next step be?