Question: Dear Ed,
I have a question about powdery mildew. My last crop, grown indoors in an 8’x 8′ growing area, 1000w HPS light, intake and exhaust fans and an oscillating fan, became severely infected with powdery mildew. I sprayed with Serenade every few days but to no avail. I have harvested all of the crop but don’t know what to do now.
I want to salvage as much as I can and have been reading Ask Ed Marijuana Gold: Trash to Stash and Marijuana Grower’s Handbook and I can’t find anything that says if it is okay to make butter out of the infected flowers. I have read that making bubble hash concentrate will remove the spores so I have started doing that but would also like to make some butter for edibles.
Your answer to that question would really help me out a lot. I do not want to ingest or have any patients that I supply for ingest something that could make them sick and need a solid answer before I do it.
Ed’s Rosenthal: Dear Donna W.,
The powdery mildew spores germinate in temperatures between 65-75 F (18-24 C) in a lightly acidic environment and humidity as low as 45%. Once they germinate they can survive a broader range of temperatures. Unfortunately these are much of the same conditions plants prefer. In the future, try a sulphur burner to prevent the powdery mildew. Additionally, UVC lights will be available for commercial use soon, which are effective in killing the spores.
When I come in contact with a powdery mildew infestation, I like to use a milk-potassium bicarbonate spray to get rid of it.
Any kind of water hash process will remove mildew and fungus spores from glands. This concentrate can be used for smoking, vaporizing and cooking edibles.
Using a dry sift method (making kief) does not separate the spores from glands, so it should not be used with infected material.
Send your grow questions to Ed Rosenthal at [email protected]