Need help here. My dad's water jasmine trees which are more than 20 plus years old is dying due to some weird disease. The leaves are withering.

Looks very dry, and is it inside? If that is roots on the surface it looks very pot bound and in need of re potting. I would look at culture first before blaming it on any disease or pest.

it looks like an iron deficiency, but maybe a lack of water and a good repotting

Hi, nope that's is not root's those are just dried grass cover on top of the soil. I notice those water jasmine with disease will have white spots on their branches

Here are few more photos for ur diagnosis.

I dont know the species. But I read online that it is semi decidious. That makes me wonders where you are, how it is cared for and for how long you have had the tree.

In general it is much better to ask why instead of what. No matter if it is disease,pests or just normal behaviour, the reason is allways environment and care.

So please tell us more about your climate and care.

Hi Tropfrog, I live in malaysia and I have those plants for more than 20 years. This is the first time I encounter this problem. My care is quite simple mainly just watering.

When was it last repotted and what soil was used?