Brown spots on leaf, Fungas Gnats?

I

Ice-R

Member
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?
 

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Dirtyc38

Dirtyc38

Active Member
Looks like nutrient burn. I have one in soil right now that got just a few spots on it like that and no bugs in my tent. Or it could be lack of cal/mag???
 
I

Ice-R

Member
Dirtyc38 said:
Looks like nutrient burn. I have one in soil right now that got just a few spots on it like that and no bugs in my tent. Or it could be lack of cal/mag???
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could be some logic to nutrient burn as i started feeding just a few days before these spots appeared. What should i do in this case? flush it now or just give water the next watering times?

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
 
Dirtyc38

Dirtyc38

Active Member
Ice-R said:
could be some logic to nutrient burn as i started feeding just a few days before these spots appeared. What should i do in this case? flush it now or just give water the next watering times?

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
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Yes flush it to were you see I want to say around 30% run off with non chlorinated water. 6.3 ph. I'm just going off memory off what I've read. Give it a couple day dilute nutrients in half and see how they handle it. These plants can take some shit so you should still be good if the get to bad in spots but still generally healthy plant. Just clip off the bad parts if in veg
 
I

Ice-R

Member
Dirtyc38 said:
Yes flush it to were you see I want to say around 30% run off with non chlorinated water. 6.3 ph. I'm just going off memory off what I've read. Give it a couple day dilute nutrients in half and see how they handle it. These plants can take some shit so you should still be good if the get to bad in spots but still generally healthy plant. Just clip off the bad parts if in veg
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thanks, have done this, lets wait and see :-)
 
I

Ice-R

Member
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)
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G

Gastheblast

Well-Known Member
Ice-R said:
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)
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You need to invest in a cheap ppm pen your plants look hungry.
 
I

Ice-R

Member
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.
 
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