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Old 06-22-2018, 12:38 AM #11
PaulieWaulie
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Originally Posted by rjrom90 View Post
A few things that helped me beat the ubiquitous PM without using fungicides:


Increase air porosity of your medium
Balance Fe:Mn to 1:1
Balance Ca:K to 1:1
Let pH swing from 5.8 - 6.5 to allow uptake of all elements
Maybe add some boron to increase Ca uptake
I usually had 30% perlite in my pro mix, and in my organic soil mix I shoot for 40 to 50%

I grow in organic soil so I hope that has similar benefits as the feed ratio (as in the plant taking what it needs)
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Old 06-22-2018, 12:55 AM #12
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Indeed, the plant should be taking up what it needs as long as the microbes are happy. However this relies to some extent on root exudates which is a result of optimal photosynthesis. Imbalanced micronutrient ratios can drastically reduce photosynthesis, but once balanced the plant will release root exudates and allow microbes to balance out the NPK uptake. Maybe try the BIG6 micronutrient pack from BuildASoil which is high in manganese with no iron added, although it's hard to say if Fe:Mn ratio is the problem without a soil test.


Edit: Forgot to say that should be plenty of perlite as long as the dust has been removed.

Last edited by rjrom90; 06-22-2018 at 01:36 AM..
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Old 06-22-2018, 02:00 AM #13
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Quote:
Originally Posted by rjrom90 View Post
Indeed, the plant should be taking up what it needs as long as the microbes are happy. However this relies to some extent on root exudates which is a result of optimal photosynthesis. Imbalanced micronutrient ratios can drastically reduce photosynthesis, but once balanced the plant will release root exudates and allow microbes to balance out the NPK uptake. Maybe try the BIG6 micronutrient pack from BuildASoil which is high in manganese with no iron added, although it's hard to say if Fe:Mn ratio is the problem without a soil test.


Edit: Forgot to say that should be plenty of perlite as long as the dust has been removed.
Sounds interesting for sure, Im open to learning more about this approach, so you are saying you are 100% confident that you currently have stock that is infected, but is not creating spores in flowering at all? And if so, how were you able to figure out that it was this fertilizer regiment that was responsible for the change as opposed to one of many variables or factors?

I guess thats what Im looking for in this post, which was to hear from people that are able to keep it from creating spores, without any weekly spraying, or that cured it 100% and are following an ipm since and have been outbreak free.

Thanks guys, good responses in the first day. This is all Ive done today, is make this post and read up.
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Old 06-22-2018, 02:10 AM #14
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Quote:
Originally Posted by PaulieWaulie View Post
Sounds interesting for sure, Im open to learning more about this approach, so you are saying you are 100% confident that you currently have stock that is infected, but is not creating spores in flowering at all? And if so, how were you able to figure out that it was this fertilizer regiment that was responsible for the change as opposed to one of many variables or factors?

I guess thats what Im looking for in this post, which was to hear from people that are able to keep it from creating spores, without any weekly spraying, or that cured it 100% and are following an ipm since and have been outbreak free.

Thanks guys, good responses in the first day. This is all Ive done today, is make this post and read up.
Check out the AEA podcasts for more information about this topic. Here is a good one to start with: https://www.youtube.com/watch?v=s5XbJEuvKS4


I do currently have plants with PM on the lower growth which has not spread past the point on the plant where I changed nutrient profiles. The new growth is very waxy with much larger leaf size. One leaf did start to get a small spot of PM but the next day it had become a small spot of necrosis, which seems to be a sign that the plant's immune system is effectively functioning by quarantining the infected region of tissue.

Last edited by rjrom90; 06-22-2018 at 07:35 AM..
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Old 06-22-2018, 02:40 AM #15
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Hi Pauliewaulie. It sounds like a living hell you have been going through and growing is not meant to be that much of a chore. I have never had PM in 20+ years of indoor so maybe something in what I have done differently to you is the key to our very different experience.

Ventilation - I think the most fundamental issue is that you vent your exhaust within your house. Air from your grow should always be vented externally so that only un-circulated fresh air is coming in. Exhaust air should also be vented from a high point in your grow space.

Strain choice - I have always grown sativa-leaning hybrids. Indica's are more susceptible to PM than sativa's typically.

Plant numbers - you seem to have a lot of plants. I usually only flower 1 or two big plants under 600w of light. Cramming lots of plants under one light, especially different strains increases the chance that one will get PM and therefore expose all the others to spore attack.

Humidity - I have never checked my humidity but I will take certain steps to minimize it when the atmospheric RH is high. When it's hot and humid I max the flow of exhaust. When cold I will use a blow heater on thermostat to maintain desired temps. This heating of the air reduces RH as well as heating the space.

Plant health from the roots up - healthy plants are better able to resist fungal attack. If you cannot maintain a perfect soil environment at all times (this takes experience and expertise) then you would be better off with run-to-waste hydro using an inert media. I hand water all my plants in a simple perlite/vermiculite media. My plants are 100% healthy at all times with minimal effort.

Insect attack - prevent rather than cure. Fungus gnats weaken the plant and damage from sucking insects (spider mites etc) allow an entry point for PM which may otherwise not take hold. I am not suggesting you have problems with these but I thought I would mention them anyway.

It seems like your only option now is to completely shut down your whole operation and start afresh with new genetics. Hopefully you can leave the PM behind as you move forward. Good luck.
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Old 06-22-2018, 02:44 AM #16
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Here is a pretty informative article talking about some of the plant's calcium related defense mechanisms against PM.

https://www.maximumyield.com/what-to...-mildew/2/1400


Quote:
So how does it work? When a mold spore lands on a plant leaf, it wants to send down a feeding tube to get to the water between the cells to germinate and spread. But when the cell walls are thicker and there is an increased amount of calcium-pectate between the cells, the mold spores just sit there.


By the time the germination tube penetrates the cells, it dries up and dies. The pectin doesn’t kill the powdery mildew, it just prevents it from becoming systemic in a plant and spreading.
Increased calcium uptake also provides a reserve of natural protection against PM. Any extra calcium a plant doesn’t use to strengthen the cell walls is pumped into a storage vacuole inside the cell. If a mold spore does happen to germinate, sensors on the surface of the leaf detect the chitin in the cell wall of the fungus. Plants don’t contain chitin—they contain cellulose.

So when chitin is detected, the plants send a signal molecule from the leaf surface down to the vacuole, opening up calcium ion channels inside the cell. The calcium ions released start a chain reaction that causes an oxidative burst—a plant’s first line of defense against PM.
It seems that PM resistance is lowered by a cellular imbalance of calcium with other positivley charged cations, mainly magnesium and potassium.
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Old 06-22-2018, 02:45 AM #17
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Going overkill on the airflow has worked for me
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Old 06-22-2018, 02:50 AM #18
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Have you used Copper Fungicide? Any pros and cons that you know of? I've found conflicting information online.
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Old 06-22-2018, 03:04 AM #19
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Hi everyone! I've always heard horror stories about PM. Is it something that is more common in the northern hemisphere? I've been Growing a long time in Australia and have never encountered it. Spider mites yes, whitefly yes, fungus gnats yes but never PM. Have I just been lucky? I hope you can find a solution and get rid of it for good.
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Old 06-22-2018, 03:27 AM #20
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Dont overwater your indoor garden! Also check the outside if there is any gardener near you who waters his or her garden too much. I did it myself once and my zucchinis died from the pm they got and affected other plants too. Try to keep the soil as dry as possible without drying them out ! Dont ever foliar spray anything but a fungicide in case of emergency early in veg . A good fungicide has to be applied only once. Milk and bicarbonate don't help much but instead are moistening the soil too much because you have to apply them every other day to keep up with the pm. It's a vicious circle. Also when watering try to not to wet the plant at all but only the soil. Better daily watering control then longer periods! Hope that helps.
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