Nice paper to familiarize and introduce yourself to some of the common (and not as common) Cannabis diseases. Most everyone will experience one of more of these during their growing quest.
There are a variety of management practices to manage or reduce the risks of infection. This table only suggests some of the basic practices, further guidance can be found on OG or elsewhere:
just got done with “barnacle scales” - plant got really “stunded” the barnacles feast up-on the plant eating all it’s energy making it very small Dam !! it was a Malawi fro Ace Got this because I used " re-used" dirt that was outside from a earlier run this year. Learned : use new soil from now on. Good info