No there is definitely insect damage, if you look at the enlarged picture you can clearly see insect bore lines. But to my (admittedly untrained) eyes, it looks like some other bug. I say this, because the boring seems larger than what a PPB might leave behind. I think the mold is there because moisture hung out in the damaged wood and gave it the opportunity to grow there, as is often the case. BUT, look at the top of the pine timber in that picture, the black staining is a clear sign of excess moisture.

I suspect what is happening here is your wood has gotten too wet, which made it susceptible to attack from larger insects as well as caused some rot of its own. The insect damage, in turn, gave the moisture somewhere to collect and hide, which led to the mold in that section.

Your real issue, I suspect, is indeed moisture. If you really want to fix the problem, than this issue needs to be solved.

How is the frame enclosed?

DLB