Q: Quite a large amount of bark enclosed in a plastic bag for about a year is covered with a whitish mold. Would this be harmful to my orchids. Would a fungicide drench be wise such as Physan 20?
A: It looks like your bag of bark was wet when filled, hence the fungus growth. It should do no harm to your plants, but the bark will be break down more rapidly then normal. After your plants are potted, you might try drenching the pots in Physan 20 at the rate of 1 tablespoon per gallon.