Mold/Mildew on frames

[NewBee]

After an inspection of one of my hives I noticed a green powdery substance on a few of the frames. Has anyone seen this before? Will the bees clean this up? Is it harmful to the bees? Should I replace the frames? We had a spell of rain and cold weather for a couple of weeks. Let me know your thoughts on this please. Thanks Steve

[Michael Bush]

I'd leave it for the bees to take care of. You may want to consider adding some ventilation to the hive by some means to prevent it in the future.