A little over a week ago I noticed what looked like a little patch of dust on a leaf of one of my plants.
It never got out of control, or spread to any bud, but in a matter of a week it had spread to all 7 plants in my tent.
I run a perpetual grow. This is my first time growing from clones. Up until now I have used seed. This is my first time seeing Powdery Mildew.
The causes are the following:
Infected clones brought into the garden
Inadequate air agitation inside the flowering tent
Humidity spikes after lights out up into the 60% range
Temperatures in the low 60's during lights off
At first I spot treated with neem. I added enough fans to make a tornado jealous. I got the humidity in check, it never goes above 45%.
I increased night time temperatures so they did not fall below 70. This kept everything under control.
I read quite a few threads and articles, pertaining to PM and cannabis, online. After educating myself I decided Greencure would be my best bet.
Greencure is a proprietary blend of potassium bicarbonate. Potassium Bicarbonate kills PM on contact, and leaves a residue that lasts for upto 2 weeks that prevents PM spores from germinating. Greencure can be used up until the last day of flowering. Unlike baking soda, which is Sodium Bicarbonate, Greencure does not need to be washed off.
I prepared a solution of 1 gallon distilled water to 1 tablespoon of Greencure. I shook it up really well, let it sit for twenty minutes, then shook it up really well again. I took all 7 plants, in their various stages of flowering, into the bathtub. I sprayed each plant very thoroughly. I got every nook and cranny, every surface area was coated.
The few spots of PM vanished. The plants looked very healthy, except most pistils turned brown. I probably should have not put the plants back under the HPS. It is recommended to spray directly prior to lights off, I believe this may be one reason why. Everything else was unaffected.
So far it has been three days and I have not seen a spot of mildew. The plants that had their pistils burned seem unaffected. New pistils have sprouted from new calyxes. I will continue to spray all of my plants, every week. I will not spray the last week of flowering, as I don't want any excess potassium affecting the flavor of my buds. I will probably try a slighly more dilute solution of Greencure next treatment, probably 1 teaspoon as most of the threads I have read seem to suggest.
I will continue to report my progress with the Greencure. I'm hoping it can get me through a few more cycles before I upgrade to a closed growing environment.
P.S. I understand Powdery Mildew is systemic and cannot be completely eradicated from an infected plant. I have read of something called Malatox that is really nasty and can, allegedly, sanitize a plant of a Powdery Mildew infection. However, my main goal is to simply keep the PM from rearing its ugly head at all. From much of what I read the Greencure will allow me to do this with minimal drawbacks. Its kind of like having herpes but never having an outbreak. Weed herpes.
Edited by rafaeltoral, 02 January 2011 - 10:03 PM.