What do you recommend if you find white rot in the attic? The decking was structurally sound and dry. The roof was replaced in 2014 with dimensional shingle and swr.
Do you recommend treatment of white rot? And by who?
White rot? That’s mold…excuse me “apparent microbial growth”. Could very well be an old roof leak, but still call it out for remediation by a mold specialist.
My termite company typically treats this “apparent microbial growth” with borate. Is that an acceptable remedy or should I keep my recommendation more general and just suggest a mold specialist?
One of the big no no’s is just sanitizing or encapsulating visible mold growth. It must be first remediated (removed), and then sanitized. Dead mold is just as bad as active mold. Borate treatment is for insects by the way.
Looks to me more that the sheathing has to be replaced in that area. Ventilation and insulation might be replaced where wetted also. You need to get rid of the mold by getting rid of the moisture problem also. Or leak. 
What would a mold remediator do aside from treating the decking with some kind mold killing agent? (assuming the decking does not need replacement)
Assuming the decking is sound and dry, mold can be removed by soda or dry ice blasting. It can also be removed by good ole fashion hand scrubbing and then sanitizing if that is the only area affected. If the deck is water damaged, it should be replaced.
Maybe an active leak. Check the roof, treat with Timbor or replace the decking.
If that area is dry then I personally would care less. There is more mold spores trapped in the insulation then that one puny spot on the wood sheathing.
The attic is not part of the indoor air quality, it is separated and ventilated externally. Getting excess mold into your living space would be possible from a contaminated attic, but it would require substantially more that what you picture shows.
Looking at the insulation colour I suspect the moisture could be coming from the home .
I would look hard to see if there could be opening or an air discharge from below hidden under the insulation , like a bath fan ,kitchen exhaust, pot lights or, Plumbing vents.
Roy, its FL. Moisture is coming in 24/7 from the humid outdoor air. 
We don’t live in the great white north.
Depending on the loan it may need a clear WDO report.
Not a water vapor problem Roy. This is definitely caused by either a past or present roof leak.
That’s my thoughts exactly. Though I’m not in Florida, that’s how I would feel about this in my area, and we get our share of high humidity in the St. Louis region.
Sorry I have seen roofs that looked like this from warm moist air from the home .
Has any one looked to see if |I could be correct .
If you have a termite company as I do, you have a license to treat all wood destroying organisms.
If there is no damage, it is just evidence on the WDO report.
If you were going to treat, I suggest Disodium octaborate tetrahydrate , AKA Bora Care.
Tim Bor is also labeled for such use as John stated.
Bora Care has better penetrating properties.
When you said “my termite company” I assume you meant who you sub out.
Sub out.
It was a pretty good sized attic so I could see the homeowner going up there to store stuff (they will be very close to this spot at the attic access).
I have recommend further evaluation / spot treatment. The decking was dry, the roof was near new.
As others stated, termite guy treats this. Should be in the WDO report
That’s what happened. It was on the WDO and the termite company will treat it.