Hi

There aren't too many fungicides left on the market anymore like Beneomyl/Funginex. There are however other less toxic products that will do the job just fine.

As long as the cuttings are already planted you can spray Safers Defender, Bio Soy or any of the Neem Oil products (Sacred Oil, Einstein Oil, Neem) to control powdery mildew.

I've also used a mixture of 35% hydrogen peroxide (Hydrox) /99.9% iso (Any Isopropyl Alcohol), water and a wetting agent (Penetrator or MagaWet) in a ratio of

30ml/1L 35% Hydrogen Peroxide
20ml/1l 99.99 Isopropyl Alcohol)
5-10ml/1l of wetting agent.

This is fairly safe for "most" plants (You'd probably want to test it on your plants first) This also kills bugs pretty good. I've eliminated an infestation of Mealy Bugs using this combo. They were fizzled out after a second spray of the above mixture.

Also another safe way for plants in any growth stage is to use a sulfur vaporizer. This hot plate device vaporizes sulfur pellets. The sulfur vapor covers that leaves and changes the ph levels ontop of the leaf surface. This causes the fungus spores to not germinate.

Another important factor in mildew prevention is to have a lot of constant air movement in the greenhouse. You want to move the air around so there is not considerable changes in air temp and humidity around the room.

One more thing that should be considered is the use of a wetting agent. This will cause the spray to form an even covering of liquid on the leaf instead of forming water droplets. Since the film of water will be thiner and have a bigger surface area of the water droplets it'll evaporate quicker. You want the liquid the evaporate as any left over water/droplets will be a heaven for mildew spores to germinate in.

Arek