Something is killing my soursop seedlings :(

[Zafra]

Hi everyone. As the title states, something is killing my soursop seedlings. I had 9 and now I'm down to 4, only one of which looks completely healthy - for now. Don't really expect to beat it this time around, but I really would like to know what it is - any ideas from the experts here? Photos of 3 stages of the disease are below (click on the first one to see it complete). Thank you!

[FlyingFoxFruits]

I wonder if it's a fungus like phytophthera?

have you possibly over fertilized them? are you keeping them excessively wet?
where did you get your soil?  was it sterile?

I hope we can figure this out!

good luck!

[Zafra]

They have gotten quite wet more than once in our torrential tropical downpours, but I thought the bags had decent drainage - maybe not? I don't fertilize at all - I use a compost/worm castings/sterile soil mix that is not sterile, but very rich in organic material. One thing I forgot to mention in the original post is that I had a devastating scourge of cucumber mosaic virus (CMV) which has the longest host list of any known virus. It wiped out most of my kitchen garden. I could easily have infected the seedlings like I did everything else, but I can find no information as to whether soursop is one of the plants affected by CMV. Does anyone know about this or want to hazard a guess?

[FlyingFoxFruits]

maybe it's some type of pathogen associated with the soil mix, being that it's not sterile....and also im not sure how well it drains (how much aeration the roots have)...the combination of unsterile soil, and poor drainage can lead to seedling death!

maybe try to use a mix that drains well...sterile if possible.

[Zafra]

Thanks for taking the time to respond. I doubt it has to do with the soil mix because I've used the same one, from the same batch, with many other seedlings of all types and not had this problem. Still wondering about CMV if anyone has any idea about that...

[FlyingFoxFruits]

youre welcome Zafra!

maybe try pulling one of the ruined seedlings up by the trunk to see if the root system is damaged.

sorry i don't know about the cucumber disease!

good luck!  I hope you figure it out!

[Saltcayman]

You could try removing the bag to see if the soil at the bottom is over saturated. I had a similar problem with bags not draining well when sitting on a flat surface. Good luck. Dave

[terejiguete]

cucumber mosaic attacks the Cucurbitaceae and Solanaceae have not seen Anonáceas attack. the viruses are very specific. and I should have a vector that carried infected plant to healthy.

I'm with asaffron, is more likely to be an infection of a vascular fungus, Phitium, fusarum .... favored by high humidity

[KarenRei]

A root check would be a pretty easy way to eliminate (or prove) certain possibilities. 

[Zafra]

Thanks to everyone for your responses! I have looked at the roots of those I've pulled and not noticed anything that jumped out at me, but I'm certainly no expert and maybe I don't know what's normal and what isn't. When I pull up the next one that bites the dust, what should I look for?

[FlyingFoxFruits]

looks for roots that are rotted...they will usually be soft, easily broken, and exhibitiing an unhealthy color...usually dark brown...rotten looking.

there won't be health white or light colored growing tips on the roots.

the soil will usually have worms and lots of moisture.