Black Spots out of nowhere!

lozac123

lozac123

Well-known member
Hi guys. Looking for some advice on my plants if anyone can help me it would be appreciated. I have attached some pics, as last year you guys wanted to see the full plant. So far this year, they have not run into any issues apart from being eaten by some insects (I think it was leaf miners, as I removed any leaves with the marks and it seems to have resolved it for the moment). So these small black spots have appeared over the course of the day. I checked the plants this morning and didn't notice it, but may have missed it. I don't think it is a deficiency, as most leaves look ok. So far they have been given:
  • Around 60g organic chicken manure pellets at the start of things. The soil is a potting compost mix, and I added the chicken manure pellets at the start of it. The plants reacted a bit much to it, and it was definitely a bit hot to begin with as the seedlings showed signs of nitrogen burn. However after about week 3 they sorted themselves out.
  • Week 6 I added some bat guano to the top soil and mixed it in lightly. Plants seem to have reacted well dispite my initial thoughts.
  • Two days ago I added some liquid seaweed concentrate to boost things.
The plants will be 2 months old on the 29th, so they are approximately week 8 today (from germ not flower). Strain isn't a MNS, but I really do value your guys' feedback hence me posting here. The black spots have appeared today on two separte fan leaves, very close to each other. I have two close ups of the spots, and several pics of the whole plant. I am mildly concerned it is sephoria, but honestly this time round I am lost with what I might have done differently in the future. I am waiting for the pots to be dry before watering, and there isnt a massive amount of humidity in the greenhouse (I think?). I have a hydrometer and it is in a greenhouse. Humidity is usually between 50-65%. Yesterday it did rain all day and was around 75% for most of the day, but I am not sure can they get fungus that quickly?

One other thing is that I have added broccoli to the greenhouse, and a mostly grown tomato plant from a family member. I have examined these for mould/ fungus/ sephoria but cannot find anything on the leaves of these plants.

Last year I pretty much lost my entire crop to bud rot/ bud mould and I want to avoid this happening again this year. I am in a different location and much better conditions though so was not expecting this kind of situation so early in the year!! We have had several weeks of rain where I live though, and it is a very wet country.


Finally, if this is worst case scenario, what are the next steps? Seeing as it isnt on any bud I am thinking perhaps I should spray it with hydrogen peroxide solution, is that a good shout? What else do you guys use?


Thanks for your help guys it is massively appreciated!
 

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Hello lozac123! :)

Check to see if the black spots are confined to fans leaves and not new growth also. Check daily until problem is solved. These unknown problems are often solved through the process of elimination. Care to guess what is first?

"Black and brown spots can appear on cannabis leaves for various reasons, most of which have simple solutions. However, growers who notice discolored patches on their marijuana plants would do well not to hang around, as rapid treatment is essential. In many cases, diagnosing and correcting the problem early makes the difference between healthy plants and a ruined crop. The majority of brown or black spots on the leaves of cannabis plants are caused by some sort of nutrient deficiency.

However, rather than rushing out to the garden center to buy more fertilizer, growers should first test the pH of their soil. In most cases, the problem has nothing to do with a lack of minerals but is instead caused by pH levels that are either too high or too low. Cannabis plants thrive in soil with pH between 6.0 and 7.0. Values outside this optimal range can lead to nutrient lockout, whereby the roots cannot absorb the nutes in their environment. Only after ascertaining that no lockout has occurred should growers consider supplementing their growing medium with extra nutrients."

I would suggest doing this ASAP in case it is a more serious problem.

Longball
 
Hello @lozac123,

I think I recognize your "problem" and you don't have to worry. ;)

I saw this many times in the past on my outdoor grows and the pictures where the spots are a bit grouped really confirms it for me.

Every black spot is in fact a fly shit.
Yes, 🪰 💩! 😅

I would clean in locally and yes hydrogen peroxide is best for this.

Greetings!
 
Thank you guys for the responses. I think Swifty was indeed correct, and it is fly poop. I noticed that there was a fly on the door of the greenhouse, and where he was were several of the same black spots! So no septoria for me (hopefully!).

I definitely think it could be flea beetles causing the holes. They seemed to have stopped now but it is very annoying! It's either beetles, or perhaps even a caterpillar, but I have not been able to find any traces of them apart from the holes in the leaves!

Thanks again all for your help!
 
There may be another possibility if the black stuff washes off.
Sometimes these black spots occur where an insect has sucked the juice out of the leaf.
Afterwards a fungus grows in that same place.
Fungus would wash off easily, fly shit is kind of sticky and hard to get off.
Fly shit would also be proud of the leaf.
These black spots look like they are a part of the leaf.

1690404104187.png
 
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