Does look like scale damage with the soot and all. And probably has attracted ants too. I've had great luck with dormant oil and malathion best applied in the soft stage but will kill the armored types by smothering them.
good read
http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn7408.html
Thanks!
I don't see too many pests on the tree besides ants. sure there are a few leaf notches and flying things, but no major plague I've witnessed. There is an ant colony living in the rootball. Do I need to kill off the ants?
Brett - you are missing the point. The sooty mold does not just appear for the hell of it.
"Sooty mold is the common name applied to several species of fungi that grow on honeydew secretions on plant parts and other surfaces. The fungi’s dark, threadlike growth (mycelium) gives plants or other substrates the appearance of being covered with a layer of soot.
Sooty molds don’t infect plants but grow on surfaces where honeydew deposits accumulate. Honeydew is a sweet, sticky liquid that plant-sucking insects excrete as they ingest large quantities of sap from a plant. Because the insect can’t completely utilize all the nutrients in this large volume of fluid, it assimilates what it needs and excretes the rest as “honeydew.” Wherever honeydew lands—e.g., leaves, twigs, fruit, yard furniture, concrete, sidewalks, or statuary—sooty molds can become established."
So, there are "pests" either on the Maha or surrounding tree(s). If there are ants in the tree, they are most likely farming what is there (scale, aphids, mealy bugs, etc.). I would personally stay away from malathion. Neem does not work well here in SFla plus at this time of year, to treat with an oil, you would need to use a product that is non-photosensitive and even so, do not spray in daytime sun or during high temperatures.