WHY IS THIS HAPPENING AGAIN?

[TomekK]

So after a few blissful months of my cacaos in their new grow tent, with all of them having fast new growth, the new leaves have suddenly started turning brown at the edges/ with spots, and some of them have fallen off. I am used to cacao sometimes aborting new leaves, but this has happened to all of them in the space of a week. Looks exactly how they looked when they came back inside (with new leaves dying), but that was most likely due to humidity while the humidity in the grow tent is very high. They were doing quite well prior to this, showing new growth for the first time this winter after I put them in the tent. Any clue as to what is happening? The three cacaos not in the grow tent don’t have this problem, and are growing well (they were the only ones that did not almost die because of the lack of humidity outside the tent).
Tomek

[Jaboticaba45]

That is why I gave up on growing cacao. My tree looks like a twig right now.

[ScottR]

water issue or soil??

[SeaWalnut]

Could be salt burns in wich case you might want to use gypsum to flush the salt.

[Guanabanus]

Cacao tend to be grown on hillsides for good drainage, and in low pH soil, usually clay.

[TomekK]

Thanks for the replies! I think it could be salt buildup or poor drainage, but what puzzles me is that it happened all at once. Within a week almost all of the plants in the grow tent, of which there are many, showed the weird browning on newer leaves/the leaves falling off. Because it happened all at the same time, I don’t know whether it’s drainage or salt buildup, as those should be longer processes, right? I’m thinking this is from some sort of shock.

I originally thought it might be shock from the neem oil I sprayed to get rid of a bug that turned out to not need getting rid of with neem (I think), but I saw this on at least one or two of them before I sprayed with neem.

Tomek

[Guanabanus]

Do you have a high-low thermometer in your grow tent?  Overly high midday temps, especially with oil on the leaves, could be a killer.  Have you seen any oil products listing cacao spray directions?

Not every plant handles oil spray well.  Carambolas can be killed with oil sprays that are safe on many other plants.

[TomekK]

How high would be too high? I probably shouldn’t have used the oil, but I used it before with no problems. But, as I said, some plants showed the damage before I used neem, though some of the others could have been damaged by the neem. How long would it take after neem is applied before damage is shown, and how quickly would the leaves die?

[Daintree]

To me, they almost look waterlogged, and maybe not enough light. 
How wet is the soil?  Maybe the grow tents are too wet.
I just grow mine in the greenhouse, where the humidity never gets over about 50-60%, and they do fine with just a daily hose-down, if I remember.  The temps range from 60 to 90, but they are in mostly shade. They seem to really prefer VERY well-draining soil.

Carolyn

[TomekK]

The not enough light look I know exactly where it comes from, being that many of the trees in the grow tent have been reduced to mere twigs this past winter, and when cacao recovers from being a twig the first few leaves are chlorotic looking. They do get enough sun in the tent.

As for being waterlogged, I agree that may be a problem, but save for two or three of them whose pots had too small holes and did look waterlogged (after this morning they have bigger holes), the rest have decent drainage, and though the soil is wet, it’s not soaking wet. But would this problem affect all the plants almost simultaneously? Some of them are in red plastic cups, others in 12 inch+ pots.

As for humidity, the tent gets probably to 80 percent on a sunny day, dropping to about 60 percent or a little more at night. I usuallly don’t have too big a problem with humidity inside, with perhaps a couple weak plants having problems every year, but this year was just unbelievably awful, with all but three plants (which are not in the tent and are doing good) suffering serious damage from humidity. I first put them under individual plastic ziploc bags, which saved some of them, before transferring to the new grow tent I built a few months ago. They seemed to love the tent, and started growing almost immediately, but now they seem to have some problems.

I usually wouldn’t be worried too much, but some of the frailest plants that barely survived the winter, especially the one that lost all its leaves twice, show this problem too, and those plants may not get another chance if they lose their leaves.

Here are some photos showing the progression of this problem:

[NateTheGreat]

They do get enough sun in the tent.

How do you know?

[CGameProgrammer]

Cacao tend to be grown on hillsides for good drainage, and in low pH soil, usually clay.

Low pH = high acidity. Clay is high pH; it is alkaline.

[TomekK]

They do get enough sun in the tent.

How do you know?

They are facing a south facing window, and the slightly translucent foil covering the tent gives them indirect sun. Last year I had one of them facing that window directly, and the leaves were burned because of too much sun (cacao does best in dappled light, plantations are often planted in between taller trees to provide shade). Also, I cannot increase sunlight any more, so it has to be enough