Mold is not good. Is it the furry type or more like powdery mildew. Mold likes a humid environment. I am not familiar with chemicals, but, here are some approaches I would try
- up the air circulation big time
- 5 T. baking soda to 1 gallon of water sprayed on all plants
- when practical set the plants outdoors as the sun's heat may destroy some of the spores
Cory, can you spray lysol directly on new plant growth? I think you can, but just want to be certain.
You may not be able to get rid of it completely in the greenhouse, but hopefully get it under control. Planting out next month could clear it up with the heat of the sun and spring breezes.

Plus, remove and discard (in the trash) any infected plant parts.

{{gwi:638897}}

V -
Thanks for the picture - that certainly looks like powdery mildew. I advise cutting off all infected parts and getting them as far away from your property as possible. (Don't forget to disinfect your cutting tools.) Spray all with the baking soda and water solution and keep it handy in case of future outbreaks. If it were me I would spray, spray, spray with this solution. It's not harmful to you or your plants.
Perhaps a bit later than you planned, but tubers and new growth should be okay for another glorious Dahlia season.
m_g

Thanks I have already applied. Lets hope this works.

I've never tried spraying the plant with Lysol- just the tubers. We use Garden Safe Fungicide3 in the greenhouse. It's rated for Organic Gardening. It's a fungicide, miticide & insecticide. We use as a preventative- about once a week I hold my breath, spray quickly all around the greenhouse, on the started tubers & new seedling babies & then get out! It seems to work as we've never had any insect or fungus problems in the greenhouse.