It’s week 8, my buds are flushing. I finished foliar feeding just over a week ago, and I have been spraying the buds with pH’ed water to help them absorb any residual fertilizer left on the surface. I am looking closely at the trichome structure… and at the base of one of the smaller plants, I notice that the buds at the bottom, in the shade,are really frosty, not just regular frosty, clumpy and patchy frosty… That means only one thing… Powdery Mildew!!!

They [spores] need the proper conditions to germinate: a surface that contains nutrients on which they can grow, temperatures over 60?F (16-20 C), high humidity and a slightly acidic environment. Once the spore senses these conditions , it germinates, sending out a hyhae which seeks out a stomata. It enters the tissue and lives off its nutrients, eventually killing the tissue. The downy mildew powder you see on the leaf is the reproductive organ of the plant, which is releasing spores into the air.
-Ask Ed

Powdery Mildew is an airborne fungus, that basically occurs everywhere with friendly conditions. It has been a pain in the ass for commercial farmers since as long as people remember. If allowed to reproduce on your buds, they will spread to any and every surface. And when smoked, powdery mildew creates any of a number of unpleasant side effects including: sniffles, runny nose, itchy eyes, coughing and sneezing, and can trigger asthma and other allergic responses.

It spreads quickly in high humidity, and in the shade, so the best solution is prevention.
Keep your humidity on the low side 35%-45%.
Turn your plants twice a week to keep any one spot from staying in the shade.
Spray fungicides preventatively through the first 5 weeks.

Many commercial sprays are available that prevent powder mildew. Make sure to use an organic fungicide since you don’t want to smoke any harmful chemicals. I recommend either Seranade or Neem Oil. Both are organic, and can be found at most nursery’s.

However, as I said earlier, I am in week 8, so it’s too late to spray chemicals. There is a natural solution. Fungii only survive within a specific pH range. Farmers used to use baking soda, and laundry deturgent to spray for powder mildew, but that sounds dangerous and a little gross. An even easier cure is mixing up a solution of 1 part milk to 9 parts water, and spray directly on problem areas. The lactic acid will kill the fungus. Powdery Mildew has a 3-5 day life cycle, so it is important to spray again 2-3 days later to kill any new offspring.

This past week has been a mess. I have been running all over the state helping a couple of friends get started. Unfortunately, in my absence, we developed a bit of a mold (fungal?) infestation. All of us were out of town over the weekend, and when we got back our plants were looking a little more yellow than usual. Upon further investigation, the pH and ppm had skyrocketed! When I first saw something slightly furry growing on the circulation pump, I asked a friend who told me not to worry, it was just nutrient residue… He was wrong. The next day when I checked the ppm it had jumped from 1800 (1200 food, 600 hard water) to 2400 (…?!). The pH had jumped tremendously as well from its usual 5.5-6 up to 7.5-8 (using the liquid test kit this is the max range on the bottle… could’ve been higher). It was in the middle of feeding, and with the res level low I could see the pump completely covered in white fuzz. In a knee jerk reaction, i grabbed a bottle of lemon juice, an began to pour it onto the pump. To my amazement, lemon juice killed it on contact, and washed it away clean. This when I realized I was definitely growing something unwelcome.

We originally believed the source of the problem was the clear reservoir. We cleaned everything out with soap, tap water (yum…chlorinated), and an entire bottle of 3% hydrogen peroxide. Hydrogen peroxide is used as an antiseptic, it is H202, basically really unstable water, when exposed to air and water, the Oxygen shoots off leaving behind water. How does this kill germs? Imagine feeding rice to a pigeon… it goes in, then pop! (sorry if the metaphor was a little grim, I got nothing against pigeons, really, I just get frustrated when my plants are aren’t healthy)

Once exposed to the peroxide, the white stuff would turn brown and dead, and wash away easily. After we had scrubbed everything as clean as we could, it took abut an hour, we put it all back together, added food and 1.5tsp hydrogen peroxide per gallon, and crossed our fingers.

Two days later… back to ground zero. pH-8 ppm-2500 white chunky stuff floating in my reservoir. I pH the water back with lemon juice, and vinegar. This time it takes a ridiculous amount of acid to return to a safe range (I didn’t measure, but I would say about 5x as much as usual). The next morning we took a trip down to The Home Depot, we figured that since the bottom tub was infected, and the top tub wasn’t, we figured the pathogen was probably really enjoying our 600w sun, and decided to switch to a black reservoir.

Once again, we removed the entire reservoir (pumps, tubes, air stones, et al.), soaked it with dish soap, tap water, and a whole bottle of 3% hydrogen peroxide, and scrubbed till our hearts were content, then threw away the clear plastic Petri dish.

With the black reservoir in place, and armed with our new friend hydrogen peroxide, and a couple of fresh lemons, we mixed up a new batch of water for the girls. They got mostly sugar and B vitamins to help them recover, and I took off to hunt down some Revive from Advance Nutrients. I picked up some Revive for a friend, and got to see it in action. He had had a tough week, he underfed his plants, then overcompensated, burned them, and created nutrient lockout. He was flushing when I got there, we added a couple hundred ppm of revive to the water, and mixed up a foliar spray for the particularly sad girls. Over the next half hour we watched as all of the yellow leaves began to return to green. Of course when I need some, its not that easy, the stores around me don’t carry it… I end up adventuring far and wide, and just gave up and crashed at a buddy’s pad.

Two days later… Its Back!!!! Finally, it’s time to consult a professional. It’s been almost a week now, and my girls are still yellow. I took a trip down to the hydro store, I described my symptoms, and how I had attempted to solve it… They were about stumped too. None of the guys there had ever seen a mold matching my description. The roots have no signs of rot or decay, its not spreading into the grow medium, it only lives in my reservoir, it makes my water super alkaline, and it won’t go away!!! Since we are in flower, using a chemical fungicide is out of the question, so the only recommendation they had was to kick it up to some industrial strength H202. Mad Farmer’s Oxygenator is a 35% aqueous hydrogen peroxide solution.

So this time we disassembled the reservoir, took everything into the shower, and poured in half a bottle of bleach and a gallon of water, scrubbed everything, and let it soak for half an hour. When you rinse it out make sure you do so thoroughly, take it into the shower, and rinse it way longer than you think you should… bleach kills living things. Once we put it all back together, I mixed up some fresh water with 1.25tsp/gal of the Oxygenator, and got the pH to 5.6 squeezing in a fresh lemon (note-possible source of contamination: unrefrigerated lemon juice can grow bacteria). Oxygenator is the business, we gave them a short 15min feeding with the water peroxide solution to clean out the root zone (just in case). I took a peak into the top table while they were feeding, and it looked like club soda, every surface was covered in tiny scrubbing bubbles, and the water was remarkably clear. I wish I could post a picture, but it wouldn’t come out.

Hydrogen Peroxide is great for killing bacteria, however it kills beneficial bacteria as well, not just the bad ones. However beneficial bacteria probably would have stopped it from taking hold in the first place. We just bought a reverse osmosis unit from ebay this week. I’ll post an article on setup, and that will open the door to a series on the benefits of using bacteria offensively

Also if we the plants were still vegetating, we could have used a mild dose of commercial fungicide. I have had good results with Physan 20. It is a disinfectant, fungicide, virucide, and algaecide, so the only living thing is the plant. Be careful, too much of this stuff will kill everything! I recommend 1tsp/gal or less, and reapply if necessary.