Harmful Bacteria/Algae on soilless medium

[lemonade]

Hey guys, I recently started some seedlings and have noticed some algae and white mould/bacteria growing on my soillesss medium (Pro Mix HP). I've never had this problem before. Should I be concerned? Initially I thought maybe the white particles were salt from my feeds; however I've only fed kelp/GH rapid start twice, and 1.2 EC GH 3 part at 1-1-1 ratio. So i doubt its salts. Interestingly, some houseplants elsewhere in my home also have this white appearance on the soil. However I inoculated those plants with BTi to combat fungus gnats. I assumed the white appearance on the soil of my house plants (looks the same as the MJ pics, minus the green algae) was a result of beneficial bacteria from the BTi. However now I'm not so sure.

I'm planning on topping soon and also transplanting into 2 gal pots with Pro Mix/EWC in about a week. I've just been scratching the surface of the soil to help it dry out faster to disrupt the fungal growth. Not sure how effective that is however. Only thing I can think of doing is using some peroxide, hopefully killing all the bacteria, good and bad. Then wait a bit after and transplant, hopefully re-inoculating the soil with bennis. Or should I not be too concerned? Is it worth it to effectively sterilize my medium with peroxide, killing any and all beneficial bacteria in the process? Thoughts?

Plants are being grown under T8's at the moment. Temp is 80f, Rh 55-65, and CO2 750 (ambient).

Here's some pics:

 

[HempKat]

I don't see any fans so it's probably the lack of air circulation combined with how peat base mediums take so long to dry out. I would try getting an organic based fungicide like this one: https://www.walmart.com/ip/Garden-Sa...ctedSellerId=0. and also put a small fan blowing from one end across the plants something like this: https://www.amazon.com/Comfort-CZ6C-...09898604&psc=1

Since the white mold doesn't appear too bad you might get lucky and the fungicide not affect the beneficial microbes since you shouldn't have to use much and the air circulation should keep it from coming back. In the future I'd wait until the plants are ready to be up potted before bothering with introducing beneficial microbes. When the plants are the size they are now and you're not feeding them much the lack of beneficial microbes shouldn't make much if any difference.

 

[lemonade]

Hey there HempKat, Thanks for the reply. I actually do have quite a bit of airflow from wall mount fans so I don't think circulation is the issue. I have a Bacillus subtilis product handy but i've never used it as a drench before. its also a few years old. I wonder how long it lasts? And would it be effective?

 

[St. Phatty]

You created a Petri dish for algae and mold - and it grew.

Mother Nature !

Wouldn't be worried, just keep an eye on Drainage and pH of run-off.

 

[troutman]

Hydrogen peroxide will kill the bacteria.

It's also possible that the holes at the bottom are not breathing properly.
I would set the pots on a tray. Algae needs light to grow. If the tops of the
pots were covered it would die.

 

[f-e]

I wonder if the other house plants were the source.
It's quite easy to promote such growth. One such way is grouping the pots as you have. It's like a continuous bed. With all that space I would spread them out a bit. Allow some air between and through them all. Once they are ready for a drink, wash the stuff in. It won't thrive in their, it's just enjoying the humid environment above the surface.

 

[lemonade]

Thanks for all the input guys! I ended up just scraping out as much infected soil as possible and discarded it.

I just sprayed the plants with Nova 40w, a systemic fungicide. I also lightly sprayed the surface of the soil. I regularly use Nova at the early stage as a preventative for fungus/mildew. One application at wk2 of veg. I know some people aren't a fan of chemical pesticides/fungicides, however I feel the risk is very slight when used in this early stage, and not used in excess,

Also this cannabis is for my personal use.

 

[Creeperpark]

You are over-watering your seedlings keeping the soil too wet. Instead of using a fungicide why don't you just weigh the containers to monitor the water intake. Overwatering is a common problem anytime you see mold or other water-born Disease. Write the dry weight and the wet weight on the top of the container on a pc of tape. When the pot almost gets to the dry weight it's time to water again and never water a wet pot. Any fungus spores that live through fungicide exposure will become resistant to the fungicide and stop working. There wouldn't be any fungus or mold or algae growing in soil with good water management.

 

[lemonade]

I appreciate your response but I'm definitely not over watering. I'm only watering 10-12L every 3 days for 50 plants. I always employ a wet/dry cycle with soil(less) and in this case I've gone to the extreme and even been let my plants get slightly wilted in an effort to eradicate this fungal growth. I have very healthy, white roots, so I know everything is healthy there. I've been growing for over 25 years and I've honestly never had this issue before.

That being said I don't have alot of experience growing under fluroros. I've only ever really used these shelves for clones before. I'm thinking once I transplant to 2 gall pots (next few days), and start running my regular HID lights, AC, dehums etc the top of the soil will dry out faster and I wont have this issue. I've just been trying to avoid running my AC.

Also the soil was a cpl years old but stored in a realatively dry environment so I dunno. Maybe there was spores in it or something.

 

[troutman]

I didn't get any algae in this grow. Sometimes I get some and sometimes I don't. I purchased 2 types of predatory mites
called Gaeolaelaps gillespie and Stratiolaelaps scimitus that are both detrivores which feeds on algae and plant debris
when food sources like thrips, fungus gnats, springtails, shore flies, root scales, root aphids, mealybug crawlers or
spidermites are not available.

 

[44:86N]

Also the soil was a cpl years old but stored in a realatively dry environment so I dunno. Maybe there was spores in it or something.

Looks like it might be a saprophytic fungus, which sometimes appear on peat mixes, especially if they contain bark, or are on the old side. I've seen that frequently in the greenhouses. I don't think it's anything to be concerned about, and will probably disappear eventually.

 

[lemonade]

Looks like it might be a saprophytic fungus, which sometimes appear on peat mixes, especially if they contain bark, or are on the old side. I've seen that frequently in the greenhouses. I don't think it's anything to be concerned about, and will probably disappear eventually.

Very interesting you mention that as i noticed this particular bale of soil seemed to have more bark/twig than usual!

 

[Cloneman]

For future starts maybe make some plastic covers like the ones I made years ago (round and square). Cut to the size of the pot with a hole and slot (to remove when up potting).
You get a great root system as well, right up to the plastic (trying to jump out of the soil) and keeps them wetterererer later on!

Pic of a frootz from just now....

 

[lemonade]

Good idea Cloneman! Your seedlings are looking nice! I like to pinch em early too. My plants are looking alot better. Just transplanted them into 2 Gal pots. As i suspected now that im running HID and AC everything is fine.

I think im going to start a grow journal soon!