Physan 20 is an excellent bactericide, fungicide, viricide and algaecide. We use this product at rate of 1 teaspoon per one gallon water of dilution and drench all our Orchids once a month. It is a good disease prevention tool. It will kill fungi and bacteria spores on contact. It is extremely effective against Crown Rot , Botrytis and is very effective in controlling algae which is the main cause of fungus gnats. EPA approved to use on Orchids and Indoor. Biodegradeable in 24 hours.A must supply for ever orchid collection.