Downy mildew? Any other possibilities?

Boston710 said:

Hey whatsup guys, noticed this brownish-tan spot on one of my lower leaves a few days ago and didnt think anything of it. A few days later, it spread up the plant a bit, and to my plant next to it so i got worried.. took off a few of the leaves, and the under-sides of some had a light coating of a dark greyish film.. couldnt get a good picture of the grey on the bottom, it was really light.. ill try to get a good picture if more appears. I have an oscillating fan pointing between them, and im growing in a diy box, with a small pc fan pulling fresh air in.. temp had reached 88 last week at the highest, and humidity is usually between 45-55% if it is downy mildew has anyone battled this? Anything i can do? Im 22 days into flower, and this is my first grow aha would hate to see them taken down from this. View attachment 3985255 View attachment 3985256 View attachment 3985257 View attachment 3985258 Thanks guys!

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Buba Blend said:

It is called powdery mildew. It does not look like that to me. Clearer pics might help, can't tell, some of it could be bug damage.

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coldrain said:

That looks like a nute problem to me, or possibly heat related. Downey mildew does not start from the edges. It uniformly zaps the entire leaf with sooty looking blotches. I have never actually seen any on a pot plant in my nearly 30 years of growing. Powdery mildew is the one you have to worry about, indoors or out.

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Boston710 said:

Alright, thanks! Hopefully its not downy mildew, real hard to find anything on downy mildew and cannabis aha.. ive been feeding with foxfarms bigbloom 15ml, tiger bloom 10ml, and terpinator at 15ml, every other watering.. also i use the gallon jugs of spring water from my local grocery store and my ph usually around 6-6.5.. i use the chemical test drops because i need to calibrate my meter, so i dont know the exact numbers.. is there anything you suggest i adjust in my feeding schedule? Thanks a ton!

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coldrain said:

Yes, the reason you are having a hard time finding anything on downey mildew and cannabis is because the two don't mingle, at least for the most part.

Your problem is definitely nute related. You are overfertilizing and then some. Cut your nutes in half and see how that goes. That will also raise the pH a bit. Mid to upper 6's is what you really want if you use commercial soil. Ideally you want the drainage to be in the low 6's and using less nutes will fix that. The test drops are fine for an indoor soil grow. You don't need a meter unless you are running hydro.

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coldrain said:

Yes, the reason you are having a hard time finding anything on downey mildew and cannabis is because the two don't mingle, at least for the most part.

Your problem is definitely nute related. You are overfertilizing and then some. Cut your nutes in half and see how that goes. That will also raise the pH a bit. Mid to upper 6's is what you really want if you use commercial soil. Ideally you want the drainage to be in the low 6's and using less nutes will fix that. The test drops are fine for an indoor soil grow. You don't need a meter unless you are running hydro.

Click to expand...