Brown spots on leaf, Fungas Gnats?

IceR · Sep 3, 2020

Started to notice in the last few days some leaves (total 7 leafs at the moment) on 2 of my plants starting to get brown spots on them, some of them just happening overnight. After reading up on what this could be (read somewhere it could be due to potassium deficiency but not really sure on this) the most likely i now think is Fungus Gnats. I have seen 1 or 2 small flies in the last couple of days that i killed (i check the tent several times a day) and can´t see any on the soil at the moment (and trying to take care to only water when the top soil has dried out) so doesn´t really look like an infestation, though the symptoms look just like i have seen on other sites showing results of this gnat. I did also find one fly in the 2nd week on the soil that i killed (you can see in in my Grow diary in the second week).

A bit about my setup:

Growtent 0.8m x 0.81m with 128 watt LED ate 30 cm distance
4 plants in soil (11 L containers)
Amnesia Haze Autoflower
germinated on 12-07-2020 on light: 18/6
started using biobizz topmax & bloom 2ml + 2ml /LT on 29 August 2020
Temperature last weeks about 26º C and 50/60% humidity
Airvent on 24/24 + ventilator

Check out more info in my Grow Diary

I thought about using hydrogen peroxide in a 1 to 4 ratio with water as explained here on groweadeasy

What do you guys think it is and what should i do about it?

Dirtbag · Sep 3, 2020

That's not from fungus gnats. That's a calcium and magnesium issue, and there is some K issues there..

Not sure what your soil is or familiar with those nutes... cant really help without a lot more info, npk, ppm, ph of the feed and the runoff etc.

IceR · Sep 4, 2020

Dirtbag said:
That's not from fungus gnats. That's a calcium and magnesium issue, and there is some K issues there..

Not sure what your soil is or familiar with those nutes... cant really help without a lot more info, npk, ppm, ph of the feed and the runoff etc.

As i am new to this don´t have the equipment to measures these (besides the water feed ph 6.8).

The soil is Atami Kilomix

ATA-organics Kilomix is a highly fertilised all-in-one soil enriched with worm fertilisers, calcium, guano and other organic substances.
This balanced soil ensures a constant supply of nutrients for a long time.

NPK 12-14-24; Mineral fertiliser.
NPK 6-7-6; Organic fertiliser.
50 L bag.

The nutrients:
Biobizz topmax: product data
Biobizz bloom: product data

in relation to lack of cal/mag: wouldnt it appear more gradually and not overnight on the leaves? And why would they start having this deficiency right after starting to feed with nutrients?

Any more help much appreciated as today another 3 leaves on 1 plant got the spots

mysticepipedon · Sep 4, 2020

You may be getting lockout. When nutrients are out of balance, one nutrient can prevent the plant from taking up another.

Im my personal opinion, that soil is too hot for reefer. You added more nutrients and sent them into lockout.

Fungus gnats do NOT do this. As reefer pests go, we'd have no problems if fungus gnats were the only problem! I have heard they can damage young seedlings, but I have never seen it happen, even with bad infestations. If you found one or two, you don't have a bad infestation.

If you ever do have a problem with them, look into beneficial nematodes. Arbico sells some good ones. But the issue you are having is NOT fungus gnats.

If I were in your position, I would do one of two things, depending on how large the plants are. If small, I'd transplant them into soil with a far lower amount of nutes, shaking away as much soil as you can, without harming the plant. If that's not an option, "leach" the nutrients out of the soil by putting them someplace where the pots can drain freely. Add 1 - 2x the mount of water it would take to saturate the soil, and let it drain out the bottom.

IceR · Sep 4, 2020

mysticepipedon said:
If I were in your position, I would do one of two things, depending on how large the plants are. If small, I'd transplant them into soil with a far lower amount of nutes, shaking away as much soil as you can, without harming the plant. If that's not an option, "leach" the nutrients out of the soil by putting them someplace where the pots can drain freely. Add 1 - 2x the mount of water it would take to saturate the soil, and let it drain out the bottom.

Thanks, i´ll probably go for the latter as it sound less invasive. After doing the "leach" option, should i continue giving nutrients the next watering cycle?

Beachwalker · Sep 4, 2020

I looked at your soil in my opinion that's not your issue because they're not small plants so they've obviously been doing well in that soil up to a certain point, also whereas you say some of the spots appeared overnight

how big are the pots you are using & what are you pH'ing your water to?

What have been your recent runoff numbers been like?

I do routine weekly flushes but I wouldn't recommend you do a heavy leeching, that would defeat the purpose of the soil, recommend you take a slurry test and post results

IceR · Sep 22, 2020

So guys a little update on this issue as it has reapeared on some of the other plants.

to resume:

After flushing the plant with the problem on the 4th September the symptoms halted and didn´t spread anymore. The next watering time i decided not to feed. And only the time after that i started giving some nutes agains, only 1/4 of the recomended amount to avoid lockout again. 1ml/lt biobizz bloom and 1ml/lt biobizz top.

A few days later around the 15th September the same symptoms started to appear again on several of the plants and as i suspect it to be lockout again i flushed all the plants, on 17th September. The symptoms seemed to have slowed down but not really stopped.

I am a bit lost as i am 2/3 weeks away from harvesting and don´t know if i should let them be and hope they will start growing the buds agains (really small at the moment) or if there´s anything else i can do?

ps. don´t have equipment to measure values in runoff water (only ph and water that i give them has been 6.8)

Beachwalker · Sep 22, 2020

Still waiting for results of a slurry test to know what's actually going on in your soil

IceR · Sep 22, 2020

Beachwalker said:
Still waiting for results of a slurry test to know what's actually going on in your soil

ok, so reading about this now. do have a ph meter so think this should be possible. will get back asap with result

Beachwalker · Sep 22, 2020

PPM really helps too, you might want to spend the 10 or 12 bucks and grab a meter, I use my PPM meter 10 to 1 or better over my pH meter

Also don't take you to sample from the top I usually dig down the side and then dig in a little bit that way with a spoon

IceR · Sep 23, 2020

have done the slurry on the top soil (3cm) and ph was 6.2.

Beachwalker said:
PPM really helps too, you might want to spend the 10 or 12 bucks and grab a meter, I use my PPM meter 10 to 1 or better over my pH meter

Also don't take you to sample from the top I usually dig down the side and then dig in a little bit that way with a spoon

any suggestions for good & affordable ppm meter. and what does this exactly measure?

Beachwalker · Sep 23, 2020

Yeah but I mentioned don't take the soil from the top; I have a designated spoon it go down the side of the pot and then I twist it and go in a little to get a scoop from as far down as I can manage, there is very little or no root damage to the plant that way

Here's 3 cheap Chinese made ppm meters in the same tap water & not one of them reads even close to the other one, and the higher the PPM of the solution the bigger the variance between them becomes

IceR · Oct 4, 2020

So finally got a ppm & ph digital meter.

As the plants were getting worse i had to harvest early and did the slurry test on the leftover plants (4 days after harvest)

Since the plants didn´t have to survive used the soil in the middle of the pot and let it soak for 24 hours. Did the test on 2 plants and these were the results:

plant 1:
ppm; 145 & PH: 6.95

plant 2:
ppm: 225 & PH 6.45

also did a 30 min slurry on a third plant:
ppm: 230 & PH 6.25

For watering the plants i use tap water that i let stand for a few days to get rid of the chlorine. So i also tested the water that i had standing (7 days):
ppm: 100 & PH 7.50

So hope this helps to find out the problem as i want to start a new grow with the same strain but a bit hesitant if i don´t know what caused this.

Beachwalker · Oct 4, 2020

IceR said:
So finally got a ppm & ph digital meter.

As the plants were getting worse i had to harvest early and did the slurry test on the leftover plants (4 days after harvest)

Since the plants didn´t have to survive used the soil in the middle of the pot and let it soak for 24 hours. Did the test on 2 plants and these were the results:

plant 1:
ppm; 145 & PH: 6.95

plant 2:
ppm: 225 & PH 6.45

also did a 30 min slurry on a third plant:
ppm: 230 & PH 6.25

For watering the plants i use tap water that i let stand for a few days to get rid of the chlorine. So i also tested the water that i had standing (7 days):
ppm: 100 & PH 7.50

So hope this helps to find out the problem as i want to start a new grow with the same strain but a bit hesitant if i don´t know what caused this.

Okay so if those numbers are right then that is fucking weird??

I'm just going to throw some spaghetti against the wall here and see if anything's sticks?

I'm not sure and I've never seen it in person but recommend you search 'cannabis brown rust spot fungus' and see if it could possibly be what you've got going on, it would account for how it's spread like that too

Also don't know anything about your newts it could possibly be a severe Calcium deficiency like Dirtbag mentioned up top but why would it lock out like that with runoff numbers like that doesn't make sense but if your nutes are lacking calcium that would account for it you'll have to check that or put up a picture of the bottles ingredients

IceR · Oct 5, 2020

Beachwalker said:
Okay so if those numbers are right then that is fucking weird??

I'm just going to throw some spaghetti against the wall here and see if anything's sticks?

I'm not sure and I've never seen it in person but recommend you search 'cannabis brown rust spot fungus' and see if it could possibly be what you've got going on, it would account for how it's spread like that too

Also don't know anything about your newts it could possibly be a severe Calcium deficiency like Dirtbag mentioned up top but why would it lock out like that with runoff numbers like that doesn't make sense but if your nutes are lacking calcium that would account for it you'll have to check that or put up a picture of the bottles ingredients

Yes weird, i agree

At the bottom the pictures of the soil i used and the fertilizers (all organic): Kilomix, biobizz top max, biobizz bloom

So to go over some scenarios:

Fungus gnat
Considered this in the beginning because of the spots, but i had so few flying around and for them to affect this mature plants in such a way i had to have a huge infestion.

Nutrient lockout
This made sense to me at the time as the first plant with this problem started 2/3 days after i started feeding (2ml/lt) for the first time (the other 3 plants were not affected this time) and after i flushed with 2 times the water of the pot the brown spots/browning stopped in that plant.
However the other plants started getting similar problem after i fed the 2nd time (this time with only quarter of the recommended amount so 1ml/lt). and even after flushing them several times the spreading never stopped + the slurry test didn´t corroborate this issue, which leads me to think this wasnt the issue.

Nutrient deficiency
If this was the case than why did it happen 2/3 days after i started feeding, that just doesn´t make sense to me (though i know so little about this vast area that maybe that doesn´t say a whole lot)

Rust Fungus
Several reasons why i think this was not the issue (after reading up on this :-):

One way to identify this is going with your finger over the leaves and seeing if some rust is stuck on your finger and i have rubbed over them while they were still alive and don´t remember any dust staying on my fingers
I have a good ventilation in the room (air exhaust & ventilators) which they don´t seem to like
As the fungus spreads it created spots but if you look at the buds you´ll see that the sugar leaves are mostly half brown starting at the tip and curling up. Not the way the fungus would spread (at least with these leaves around the buds)

Maybe a combination of several issues?

Anyway help is much appreciated as i want to start a new batch without running into the same problem.

Beachwalker · Oct 5, 2020

I will read everything when I get a moment but my thought on this is It's Your nutrients I see other people having problems with bio bizz as well, now granted I know nothing about them, aside from what I read about them on their website before I replied to you the other day

but when it looks like a nutrient issue, when other people are having nutrient issues with the same nutrients maybe it's a nutrient issue ?

Also when you said this I noticed it

"And why would they start having this deficiency right after starting to feed with nutrients"

..I said maybe LOL hope we can figure this out maybe we can give this thread a bump if nothing else and get some people more familiar with your newts to post

Another thought is that looks like a pretty potent soil I looked it up the other day but I see you posted it above and I'm going to check that later too

Edit: the only time I've had leaves die off like this was when I did my first soil grow 5 years ago and my soil PH was very low which has been ruled out by your readings

Beachwalker · Oct 5, 2020

I was just scanning through your pictures and maybe I missed it but I wanted to ask you about the label on your nutrients, where is the calcium and magnesium??

IceR · Oct 5, 2020

Beachwalker said:
I was just scanning through your pictures and maybe I missed it but I wanted to ask you about the label on your nutrients, where is the calcium and magnesium??

I guess they don´t contain any :-(

As i am new to this gardening, i understood that the more easy way to start was with soil & using organic nutrients because this was the way i would encounter the least problems. Apparantly not completely true... :-)

Do you think this could be the issue?

Beachwalker · Oct 5, 2020

Dirtbag said:
That's not from fungus gnats. That's a calcium and magnesium issue, and there is some K issues there..

Not sure what your soil is or familiar with those nutes... cant really help without a lot more info, npk, ppm, ph of the feed and the runoff etc.

^ so as always mr. Dirtbag nailed it right away but now the question is why is this happening?

Your runoff numbers are very low so your plants were starved; there was probably more than one nutrient deficient and they showed it

So not knowing anything about your nutrients I'm going to recommend some PPM ratios for small medium and large plants

But first now that you have the PPM meter can you check what the PPM of the basic nutrient solution you were feeding in bloom was?

Beachwalker · Oct 5, 2020

IceR said:
I guess they don´t contain any :-(

As i am new to this gardening, i understood that the more easy way to start was with soil & using organic nutrients because this was the way i would encounter the least problems. Apparantly not completely true... :-)

Do you think this could be the issue?

Your nutes don't look bad you can definitely work with them plus they've got humic and fulvic but you're going to need to grab a bottle of GH Calimagic, I recommend this brand because it's a different kind of calcium and I like it better but any product will work I'm sure biobizz makes their own calcium/magnesium supplements as well

Brown spots on leaf, Fungas Gnats?

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