Question
Hello John, from one 'Expert' (I'm in real estate) to another, thank you in advance for your time.

I am nursing back to health, an adopted 'flat' braided ficus bengimina of 8 stems and 5 feet in height.  It's age is unknown, I've not repotted it at this point and it lives in a 12' clay pot.  There are light signs of white chalky residue on the exterior container sides which I presume to be salt deposits.  Since beginning my weekly feeding of Peters began, new growth has sprouted everywhere and it's beginning to look rather proud in spite of the problem.  

The problem; On all the original and older leaves and now younger ones, beginning from the outer tip and moving inward toward the stem are a kalidescope of tiny yellow dots which I presume to be the indication of collasped cells and the occupation of spider mites.  Upon close inspection in bright sunlight with unaided eyesight, one sees no visible evidence of webbing nor is there any sticky residue when running a finger along the underside of the leaves as one would expect to find from a sucking insect.  There is also no scale present on the stems.

I noted this on what few leaves existed when I was given this plant and now that the new folige is also affected, I wonder the possible cause and treatment.  Since the new growth is so prolific, I ruled out a root disorder or nematodes and there really is no place where I live to even test the soil for them.

I am living in Cabo san Lucas at this point and locating what control measures one normally finds at Home Depot or a garden center is not always the case.   

Thank you again for your time and advice,
Rick Stone

Answer
Hi Rick,

It is obvious that you are an avid gardener as you are right on target with your observations.  

As for the lesions on the leaves, these could be the result of a fungus infestation.  Monitor these lesions over the next several days to weeks.  If they appear to grow larger with a definite halo around them, then your ficus has anthracnose, which can be caused by several fungal species: _Glomerella cingulata_, _Colletotrichum_ spp.  

As disease develops, these yellow lesions will enlarge and become black.  Eventually the affected leaf will fall off the plant.

There are many times that leaf spots are caused by environmental conditions, so their appearance may be transitory in nature.  As the tree adapts to better environmental conditions, these spots may abate.  Your feeding regimen might also include micronutrients: magnesium, calcium, iron, etc.   As you mention, these may not be readily available in your area.  Many of these micronutrients can be supplied simply by adding some humus or top soil to the potting mix.   Alternatively, you may search the web and find alternative products.  For example, Epsom salt is an excellent source of magnesium (1 tbs/gallon water).  Iron can be supplied by adding iron table (such as FemIron) to a gallon of water.  

So, the bottom line is:  wait and see.  If your plant develops any of the signs of fungus infection, there are sulfur products that can limit the spread.  There are also some specific fungicides that work well.  But let's not rush to use those chemicals.  One thing that you can do to limit the spread (if this is fungal in nature) is to remove the affected leaves and burn them.  Remove the dead leaves.  When these lesions are present, water only from the bottom of the plant as the water splashing on affected leaves can dislodge spores and transfer those spores to unaffected portions of the plant.

Hope this hasn't been too much information.  

Good Luck and Good Gardening.