Yes you can solve this problem. The inside of the hood should be painted or sealed. You will be surprized at how much more light you will have if you paint the inside white. Also, the wood will last much longer, because the paint will seal out the moisture, keeping the wood from rotting.
Remove lights and ballasts, all electronics in there. Get some outdoor grade white paint. (I used Killz brand paint, covers mold, I think it somewhat prevents it.) Paint the inside of the hood covering everything very well, 2 coats. Let dry thouroughly, re-install hardware, and you are back in bidness!
For the record, the inside of my diy
canopy does get a bit of mildew/mold on it, but not much. Not enough to give it much thought.