I have several citrus trees, all young trees less than 5 years in the ground.
The lemons, Satsuma Tangerine, and Valencian Orange trees only have trouble with needing magnesium and calcium added to the soil.
Dolomite takes care of that.

My 2 Honey Tangerine trees, what I believe is a Fremont or Dancy Tangerine, and a Kaffer Lime tree are all badly affected by canker and/or something else.
There is also a new Tahitian Lime that is not showing any symptoms yet.
But, I am concerned for it.
The tangerine fruit still taste OK, but their skins are badly marred by the infection, and their size is reduced greatly.
The newly formed leaves are also infected by what I think is the same thing.
They have small galls on them and curl up.
It does seem to affect the trees' ability to hold fruit to maturity.

I have read somewhere that the Honey Tangerine will become more resistant as the tree ages.
I have used Neem Oil on them occasionally.
It does seem to work, for a while at least.
I do not want to begin spraying pesticides regularly to control this problem.

Is there a way to deal with this?