I does not look like mold to me. It looks like someone painted the area with a brush with white something to treat the "infected bug area". You can still see the grain of the wood through the paint, mold usually raises off the surface in a bulge, too. The off colored pine is from where the timber sat through the summer and is a variety of blue stain. I see a lot of it and in different stages of development. I do not suspect water damage, the dry wall look just fine, there would be some staining there as well. The bug paths do look like pine drillers/bores, maybe ants. If I have sawn logs with drillers in the log and left the lumber flat stacked for too long of a time you will see where the worm has come out from the wood and chewed along between the two boards leaving a similar pattern. But I don't know how this could have happened in this set up after the cutting of the frame. Was the tunneling present when the frame was cut?
Any chewing present from recent work, poo from the bugs? How big or small is the frass?
