What is it and how to treat

Some photos of a Skywalker OG, week 7, day 3 of flower. This plant has been mostly problem free until I spotted something on just a few leaves. Don't know if fungus or insect. Any help would be appreciated. Thank you,.

Here is a close-up of one of the leaves:

I am at a loss. Checked leaves, no insects. I tried a 3-in-1 spray by Safer which works on insects, mites, and fungus. I removed all of the damaged leaves (only 4) and sprayed the top of the leaves. I checked top & underside of the leaves, and noted damage just on the tops. Will check tomorrow and see if problem persists.

Looks to me like too much N for flower..

The3rdMan said:

Some photos of a Skywalker OG, week 7, day 3 of flower. This plant has been mostly problem free until I spotted something on just a few leaves. Don't know if fungus or insect. Any help would be appreciated. Thank you,.

Here is a close-up of one of the leaves:

View attachment 5286969View attachment 5286969

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That plant is way overfed. Nitrogen toxicity.

Looks kinda like the dreaded downy mildew to me. You will see it spread and start with a single dot or two but the spots spreads fast.
Unfortunately it’s not an actually fungal infections so most treatments are not going to help. Typcailly comes from clones source or, when grown in soil during veg with lower temps and higher humidity it likes to pop up.

O and if I am onto something. The only treatment is cutting out affected leaves and cleaning environment, then starting with new seeds instead of clone.

Also as other said the N toxicity should be addressed as over fertilizing N can increase pathogenic diseases

Thank you, appreciate the comments.

that doesn't look like any kind of mildew...that looks like too much N and not enough Calcium...

Roger A. Shrubber said:

that doesn't look like any kind of mildew...that looks like too much N and not enough Calcium...

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It’s not technically mildew or mold. More along the same taxonomy as algae. It’s often mistaken as ca deficiency but only affects certain parts of the plant instead of globally. You’ve seen it on most green leafy vegetables and most never know it, or mistake as deficiency.


I could be wrong but I have seen it first hand a couple times and it’s pretty unique in its damage.

The3rdMan said:

Thank you, appreciate the comments.

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hey just for my curiosity flip the leaf over snd take some close ups of bottom side where that damage is. There typically will be a grey/darkish spots that may not be super noticeable without a scope.

green_machine_two9er said:

It’s not technically mildew or mold. More along the same taxonomy as algae. It’s often mistaken as ca deficiency but only affects certain parts of the plant instead of globally. You’ve seen it on most green leafy vegetables and most never know it, or mistake as deficiency.


I could be wrong but I have seen it first hand a couple times and it’s pretty unique in its damage.

ake a look when lights are on tonight.hey just for my curiosity flip the leaf over snd take some close ups of bottom side where that damage is. There typically will be a grey/darkish spots that may not be super noticeable without a scope.

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I had deleted the affected leaves from a couple of days ago. I have not seen the problem reappear. Maybe the 3-in-1 spray worked. If the problem resurfaces, I'll do as you suggested. Thanks.

Regarding the nitrogen excess comments, it does not appear to me as excessive as some commenters have said. I would classify it as a mild nitrogen excess. I see some leaves turning lighter green as the plant is approaching harvest. The excess was due to adding 1/2 cup of 4-4-4 to some fresh happy frog at the beginning of flower. I will modify next time and only add 1/4 cup of 4-4-4. It is better to under fertilize and add more later if needed. I'm still a beginner.

Excess nitrogen has blocked phosphorus.

hotrodharley said:

Excess nitrogen has blocked phosphorus.

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I did have a P def couple of days ago because I stopped feeding the plant. Fed 1/8 tsp of Phosphorus 9-61-00 and it appears to have resolved that deficiency.

The3rdMan said:

I did have a P def couple of days ago because I stopped feeding the plant. Fed 1/8 tsp of Phosphorus 9-61-00 and it appears to have resolved that deficiency.

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That’s what that leaf is showing.

I agree with these guys with the toxicity and nutrient issue but I'm guessing you have a pet. Looks like some hair on there and that's a good way in for pests. Not that you have them just a heads up.

You guys are very observant.

If you're not using calmag you need to. But it seems to me other parts of the plant would be effected as well. Could adjust light or plant some. Your ph looks good. Go ahead and remove the fan leaf.
And keep it moving. Always keep silica blast on hand too