Help with leaf spot diagnosis

maxvooo · Mar 13, 2020

Could this be a fungus? Could this be a pH problem?

This is a Donny Burger veg plant about 3 weeks old in Foxfarm Ocean Forest soil. The only supplements added so far are Foxfarms Grow and Vitamin B-1 both in mild doses. The light source is a 1000W LED. The temp and humidity have been steady at 65-70 degrees and 50-60%. There are six different plants in this space all different strains. All of which looked fantastic until two days ago. Suddenly today only the Donny Burger plant came down with these spots.

DreamsOfDiesel · Mar 13, 2020

Phosphorus deficiency? Could be PH related. Havent seen a fungus do that. More experienced ppl here than me, they will chime in soon

Ruefuu · Mar 14, 2020

Almost looks to be a calcium deficiency to me. Maybe a little more cal-mag or if you're in soil bump the Ph to 6.8 for your next watering and then back down the watering after that and see how she responds

Beachwalker · Mar 14, 2020

Yeah I agree I don't think it's a fungus, not sure what deficiency but I see leaves curling so I want to know about your pH & your medium

Also what are you spraying on those leaves?

Jimster · Mar 14, 2020

The damage almost looks like something physical caused the damage, like what @Beachwalker mentioned... are the leaves just wet or are they covered in something. If leaves overlap and get water between them, if you don't have enough airflow, it can cause spotting, but I would expect it in more than one plant.

maxvooo · Mar 14, 2020

More Info:

Donny Burger
Indoor
5 feet x 7 feet x 8 feet (8 feet is the height)
Soil - Foxfarms Ocean Forest
water pH is 8.4, runoff pH is 6.4
Foxfarms Grow & Vitamin B-1
Temperature 64-72 degrees - taken at plant level
Humidity 45-60% - taken at plant level
1000W LED 24 hours
440 CFM 6 inch inline duct fan and carbon filter.
3 weeks vegetative growth
Additional info - see my brief original post comment
Whole plant picture

Formallyhap · Mar 14, 2020

If you're watering to run off you may have used all the buffering capacity of the FF soil.
Did you add lime or just use it straight?

If that was my plant, I would top dress with some lime and then water with molasses.

maxvooo · Mar 14, 2020

Additional pics

mancorn · Mar 14, 2020

I don't see from your original photos that the problem occurs across/covers a leaf vein, which makes me think it's not a fungas or mold. In your last picture it looks like a "burn" area across a wide section of a leaf, which makes me think that is caused by something applied to the leaf.

Beachwalker · Mar 14, 2020

maxvooo said:
More Info:

Donny Burger

Indoor

5 feet x 7 feet x 8 feet (8 feet is the height)

Soil - Foxfarms Ocean Forest

water pH is 8.4, runoff pH is 6.4

Foxfarms Grow & Vitamin B-1

Temperature 64-72 degrees - taken at plant level

Humidity 45-60% - taken at plant level

1000W LED 24 hours

440 CFM 6 inch inline duct fan and carbon filter.

3 weeks vegetative growth

Additional info - see my brief original post comment

Whole plant picture

Water pH is 8.4

At least three of us have asked what your spraying because if it's more than water then as was said above that could have caused burns; if they're not burns then I suspect your high pH may be involved, recommend taking a slurry test & posting results, good luck

1badcell · Mar 14, 2020

Use a ph pen
Let tap water stand in bucket for 36 hrs before use.
Use a fish tank bubbler to oxygenate the water if possible.
PH down water to 6.8 before adding chemical fertilizer.
Less fertilizer is better. I use it to change ph if needed.
If done right

maxvooo · Mar 14, 2020

Beachwalker said:
Yeah I agree I don't think it's a fungus, not sure what deficiency but I see leaves curling so I want to know about your pH & your medium

Also what are you spraying on those leaves?

It's plain water you see on the leaves at the time photoed. I was spraying the bottoms of the leaves.

maxvooo · Mar 14, 2020

Beachwalker said:
Water pH is 8.4

At least three of us have asked what your spraying because if it's more than water then as was said above that could have caused burns; if they're not burns then I suspect your high pH may be involved, recommend taking a slurry test & posting results, good luck

It was plain water on the leaves. I was spraying the bottoms of the leaves.

maxvooo · Mar 14, 2020

mancorn said:
I don't see from your original photos that the problem occurs across/covers a leaf vein, which makes me think it's not a fungas or mold. In your last picture it looks like a "burn" area across a wide section of a leaf, which makes me think that is caused by something applied to the leaf.

I was cleaning the cover to the carbon filter right before the leaf spotting occured. Still only one plant was affected. It was the closest one.

DreamsOfDiesel · Mar 14, 2020

maxvooo said:
More Info:

Donny Burger

Indoor

5 feet x 7 feet x 8 feet (8 feet is the height)

Soil - Foxfarms Ocean Forest

water pH is 8.4, runoff pH is 6.4

Foxfarms Grow & Vitamin B-1

Temperature 64-72 degrees - taken at plant level

Humidity 45-60% - taken at plant level

1000W LED 24 hours

440 CFM 6 inch inline duct fan and carbon filter.

3 weeks vegetative growth

Additional info - see my brief original post comment

Whole plant picture

Ph way too high

mancorn · Mar 14, 2020

Any use of a (copper) fungicide at any point?

maxvooo · Mar 16, 2020

Formallyhap said:
If you're watering to run off you may have used all the buffering capacity of the FF soil.
Did you add lime or just use it straight?

If that was my plant, I would top dress with some lime and then water with molasses.

I added some perlite to the soil but otherwise used FF soil straight. Interesting you asked me if I used it straight or added lime. Do you regularly add lime to your FF soil?

I did a slurry test of the soil in two plants and found pH 5.4 and 5.5.

maxvooo · Mar 16, 2020

maxvooo said:
It was plain water on the leaves. I was spraying the bottoms of the leaves.

I did the slurry test two plants and found the soil pH to be 5.4 and 5.5. Is that what FFOF soil tends to run?

Beachwalker · Mar 16, 2020

maxvooo said:
I did the slurry test two plants and found the soil pH to be 5.4 and 5.5. Is that what FFOF soil tends to run?

No it's usually 6.5 but I found it drops especially during flower or after a lot of heavy feeding. I add one level tablespoon of dolomite per gallon of ffof . I would recommend you water in one level tablespoon next watering and then check it again with either a slurry or the runoff before adding more, but that's a good place to start, because you don't want to add too much dolomite at once, good luck

maxvooo · Mar 25, 2020

Beachwalker said:
No it's usually 6.5 but I found it drops especially during flower or after a lot of heavy feeding. I add one level tablespoon of dolomite per gallon of ffof . I would recommend you water in one level tablespoon next watering and then check it again with either a slurry or the runoff before adding more, but that's a good place to start, because you don't want to add too much dolomite at once, good luck

Thanks much for the comment. I was going to try your suggestion. By the way I have added very little nutrients to the starting soil. Almost every watering to date I have used plain old water out of the sink. Of course water does not have buffering capacity. The water is about pH 8 going in. You can change the pH of plain water with a drop of something like pH down. And of course the soil alters the pH of the plain water immediately as you can measure in the run off. The last two waterings I simply poured out the run off in the trays rather than letting it soak up back into the pots. I guess you could say I am "flushing" the soil a bit. Sure enough, the pH of the soil came up already to about 6.3.

Help with leaf spot diagnosis

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Help with leaf spot diagnosis

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