Abiu tree's slowly dying

Bangkokii starts with ...
Again my abiu's in raised bed full sun are slowly dying, branch by branch is getting black and dead.

What can cause this? i have a few options:

1- root rot, the raised bed is 30 cm high, under that is clay and the waterlevel is about 50 cm under the clay. Avocado grew very well on the same spot, so does durian.

2- some infection, there are always insects on the tree.

3- too hot and too much sun..i live in Bangkok.

4- not enough potassium/zinc....the leaves look light green but got smaller since 6 months.

I had loads of abiu's dying here but i won't give up trying..All help is welcome..thanks in advance.

Bangkokii says...
Mark the abiu's were 2 and 4 meters away from where i had my huge avocado which never had any issues and grew too fast but never bloomed.

I took the abiu's out and planted them in large pots with sand, pumice and some peat/pinebark chips.

They had almost no roots left.

I'll plant another durian on the same spot but make an extra high mound for it. Also a pulasan will go in...

Abiu's are not easy to grow here but i'll get there...

Your avocado looks very sad, i had some in pots which looked much better.

Bangkokii says...
Yes that looks better Mark.

I treated the abiu with a 1% soildrench of neemoil and also sprayed it with a 30cc in 10 liter mixture.

Plus i gave it potassiumphospite to stop the rootrot.

They are still alive but look very sick.

Now i don't dare to plant pulasan on that spot, maybe it gets rootrot as well. So i planted another durian there, can easy buy those.

In that raised bed are still old avocadoroots, they don't rot away for a year now. Maybe those caused the rootrot? Anyway i will only grow abiu in pots with much sand from now on but they also did well in pots filled with loam as long as you don't water too much like me by automatic sprinklers.

Bangkokii says...
One abiu is in a new potting mix with loads of pumice and pinebark..it's alive but that's all said and done.

I'm starting to think that it's too hot here in my garden for abiu's.

I have a cocktail abiu tree now with 3 varieties on it (my last good tree) and i put it in full sun but it's not happy.
Especially the Z4 has yellowing leaves but also the one from melbourne has new leaves dying. Might be sunburn but i think i'll put them on the back of the house where they get 4-5 hours sun a day...in the past they grew well there but maybe never bloom.

There's a lot of contrary info about growing abiu on the web, some say they need wet soil, others say sand...max temp for them is 38 i read but i get that every day in the sun.

White jaboticaba can stand the heat easy and even likes it.

I hope abiu fruit is worth all the hassle, i've killed more than 10 so far.