what is the best way to deal with powdery mildew in a systemic form?
First you realize that if you are cloning that PM is a monster that can only be beat with proper treatments lasting months to save a particular rare strain.
Let's say you have a plant with PM, then you need to veg it while treating the soil with H2O2 3%, as it grows spray the entire plant with Zero Tolerance fungicide/pesticide diluted according to the label, treat soil as well.
This can be applied to all surfaces including cloning trays, etc.
Be sure to treat all fans, walls, floors, physical objects in the room with a light bleach water solution 1-2 cups per gallon, do not spray your plants with the bleach water solution and be sure to ventilate while doing so.
After some veg growth, take the topmost cuttings with the least amount of PM, clone those and then repeat the cloning process after veg growth has been established. Add 1-3 caps of H2O2 per gallon to all watering solutions.
You will notice that during the second stage that the PM inhabits the lowermost leaves and infects the new growth later. This progressive spread can be stopped through selective uppermost cloning repeats, which effectively removes the PM infection from the plant by out-growing it.
On the second or third cloning cycle the fresh growth will have some branches that are completely free of PM. Clone those shoots and repeat, after the third or forth cycle of this while applying zero tolerance to the entire plant and using H2O2 in the watering you will outpace the infection and effectively remove it during suppressive treatments.
Increase outside air pass-through in your grow room, allow for an exit vent down low in the room, this will help remove spores I call it a "particle vent", adjust your incoming air so that when it enters the room it causes the air in the room to spin around the room so that the larger spores are removed and get stuck to the walls or fall out the particle vent(s).
Use more MH than normal for a while, it has a strong UV signature and can help keep infections from re-occuring, install an Ozonator on the outlet vent allowing some UV to spill into the room for longer term prevention, just be sure to turn off the Ozonator before entering the room due to strong UV's which can damage your eyes and skin.
if you do these things you can save any strain, and keep your room free of mold and pests through preventative treatments. Spray your veggin plants once or twice a month with zero tolerance and on flowering plants cover the trunks with red cayanne pepper extract to prevent mites and molds.
If in flower: treat with zero tolerance, finish bloom cycle and then start with new seeds or cuttings and if infection occurs, follow above instructions.
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