Mike,
Can you check the pH of the trees that are dropping figs and compare to the other containers?
I have also had differing pH in containers of potted trees from the same batch of potting mix due to the leached water from the mulch that was used.

<edit> A pH change is sometimes enough to change the absorption of nutrients to the fig trees.
Acidic pH affects the absorption of Macro nutrients and Alkaline pH  affects Micro nutrients, this can make nutrients less readily available for use by the roots and can lead to many symptoms of nutrient deficiency. From my observations, there are often several varieties that behave differently given the same culture and by adjusting nutrients and or water they will often respond better.
 

Ii'd agree that it's not heat stress. I have mine in black containers in full sun in searing temps with months now of 100+ degree temps. Even the 1 gallon ones are doing well. I still have some fruit drop on some of the ones where I didn't realize my auto irrigation failed. I tried an experiment last yr and fertilized 5 fig trees out of 100+ trees. I used Schultz 21-0-0 ammonium sulfate. Only sprinkled a few teaspoons on the 26.5 gallon pots. Must have over did it because all of them dropped fruit and leaves turned brown and fell off. This yr I just put compost over all the trees and mulch and most of them have done well. Had a nasty monsoon last week. After that most figs are swelling and ripening now. Some soured but the rain mostly helped.

Pete, my toy PH tester says 7.9 and 8.1 on the two in pots that are dropping the figs. It read 8.2-8.4 on my 12 best performers so far this year in 10-15 gal pots.

what brand/type/formulation of fertilizer you using ?

It's still all speculation.  

Personally, I wish I knew what I needed to do (culturally) so that I could consistently grow my trees at their optimum potential.  I'd be willing to do whatever it would take, for the short, 3-4 month growing season, to get some better results.  But, in reality, what could I/we control?  Only watering and fertilizers.  Weather, ambient temperatures, sun light, day length, etc....is up to Mama Nature.


Frank

hungryjack, I can't see that being relevant. Six trees out of 150 acting up. Two in the ground, two large pots and two pots buried 6-8 inches in the ground. All the others are doing fine.

I should probably write it off to mother nature and move on.

Mike,

Have these trees produced in the past?

Rafael,

Unless your white containers are opaque, they have the potential to trap more heat than black ones.

James, yes they have.They are all 3-5 year trees also

It is purely a guess as I have not experienced this or seen anything written before.  There are times when a tree will start to produce fruit then abort in response to some stimuli.  I wonder if there was some minor cold damage to the fruit buds that was not severe enough to stop the tree from starting the fruit, but later triggered an abort response. 

James, thats another good theory for the two in ground trees. The other four have not been exposed to the cold so wouldnt apply to them.

It looks like these plants were stressed to the point they dropped their fruit. 
Could you have been too efficient with watering and ended up with some roots that that suffered some rot?

Usually I have seen figs drop from either inconsistent watering or dramatic temperature shifts. Sounds like you are keeping the soil moist and mulched so perhaps it is the temperature. My figs are organically grown and I still have a few figs drop.

Mike in Hanover, VA

What varieties are dropping the figs?  I am just curious what they are, since you have had figs from them in the past I doubt the variety is the issue but perhaps as mentioned before, there may be a climate issue during the season so far that fluctuations have caused, although boron is less available at those pH's you have, I don't know if it can cause figs to drop like in tomatoes (tomatoes with insufficient boron will have fruit fall) and since you have said you switched to all organic, maybe your fertilizer doesn't have enough boron?  Again I don't know if boron can cause fig fall but I am familiar with tomatoes so that is where the idea came from.

Chivas, the two in the 15 gal pots that are dropping are Macool and Orourke.

Cut open falling fruit from my one tree that is struggling to keep its fruit

Is it rubber like and wrinkled on the outside?

Very good information, thanks for sharing.

Best,
Tam

Pale yellowish w some wee spots. Not sure about rubbery.

Wrinkled, yes. I'm not going to begin to pretend I could diagnose a nutrional issue, this plant is in a Bill Sip. 2 theories: 1. Crowding-2 strong plants on either side in a tight space; 2. If it is possible, this young plant may have set more fruit (about 70) than its root system could handle.

Your pH is way way too high. Your pH is the problem. Makes pretty plants but no RIPE fruit. You'd be surprised those who don't check pH.

I'm having just the opposite affect.......2 trees are getting too much water and not enough nutrition. Leaves are yellowing and it's raining daily! I just remove the leaves and give it nothng for a week or so. Leaves pop out days later, and fertilizing starts again with liquid feed till end on month.

I have a meter, I will check ph and post result. There is some pelletized lime in the soil and not much leaching because it is a sip w a single drainage hole.