white powder substance on rockwool?

A week ago I noticed that one of my plants (Critical Jack) had some algae growing on it's exposed rockwool cube. I cut the algae off and covered up the cube with hydroton so as to stop light from hitting the cube. Today I was checking on the girls and I decided to see if everything was okay on the cube of my Critical Jack plant. So I brushed aside some of the hydroton over the rockwool and found a white powder like substance covering alot of the cube. Does anybody have any idea what this is? Is it harmful? How to treat it? It doesn't really seem to be hindering plant growth at all. Also the bottom of Critical Jack's stem looks a little beat up but I'm not sure if that's from this white powder or just from having all the hydroton around it. I have another plant also in rockwool and nothing has affected it so far.

Ewwww mold. Gross man cover that shit up. You gotta keep the rockwool out of light, put some more hydroton on top of that or even better a lid.

It'll be fine, it's not much it looks like. Just take care of it now before it spreads down to your roots.

VoidObject said:

Ewwww mold. Gross man cover that shit up. You gotta keep the rockwool out of light, put some more hydroton on top of that or even better a lid.

It'll be fine, it's not much it looks like. Just take care of it now before it spreads down to your roots.

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Cover it up, it could also be an indication that you have to much salt buildup on the growing medium, as long as it doesnt flourish, you will be okay!

its definately mold. i agree with dude above, cover it up thoroughly. dont ever let light hit your deeper levels of growing medium.

1. Put plenty of low pH flushed hydroton above the rockwool cube. keep your humidity levels down a little bit as that may cause mold.
2. watch and see if the powdery substance grows unto the new hydroton cubes that you placed.
if the mold isnt growing into the NEW hydroton pebbles than you have sustained the issue.

now, you need to watch closesly and see if this "white substance" pokes hes head again. if so, try a flush with H2O2 pH 5.8 water and hygrozyme. let that ride for a few days and keep us posted on the results

Its mold & powdery mildew,i'd bet you have humidity of 50% or better,the big problems will come in mid bud if you dont get a handel on shit right now.

Any strain in the CRITAL MASS line which is just another name for BIG BUD is highly & i do mean highly suseptable to grey mold aka bud rott in mid to late bud.

Dont just cover that mold up either,a single mold spore lodged inside a fat bud will bring down a whole crop,ive been there & its bullshit.

Get that plant out of the area asap,clean everything in the area & get some fans circulating fresh air,fresh clean air is 2nd to only pure ozone in killing mold,the fan/fans will knock down any spores,mold spores are in every grow room on earth its weather they lodge in a stagnant atmosphere that determines if that spore turns into a mess.

Cut away any of the rockwoll covered in mold & spray the remaining rockwool with a 50/50 mix of regular 3% peroxide & water then rinse the cube by dunking it in clean water,do not squeeze the cube.

You've got an issue that is only going to come back & in alot more destructive manner if you dont fix whats there now plus take corrective action.

Mold/mildew stem from stagnant non flowing air teamed up with wet conditions,hydro is very susseptable to powdery mildew & mold,you need to lower humidity & get alot more air flowing,the member who suggested a lid gave you excellent advice,all my trays are covered for such reasons,i also spray all my plants durring late veg with a liquid copper spray soaking them heavily,then i never mist again.

If a lid isnt possible then at the very least cut squares of white plastic & cover the cubes to prevent the cubes from turning into a breading ground.

You can purchase Neoprene inserts that just slip over the top and block light from the source, light+water+bacteria=mold like they said above, take care of it now and it wont cause you any problems in the future!

Well as an avid user of Rockwool I would have to say from experience that that is in fact NOT MOLD! It is left over salt residue from the fertilizers as I use thin rubber squares to cover my netpots and commonly have the same stuff with roots growing out of them. I can take some pics if you want. Green algae looking stuff..bad...light and heat problems.

Go ahead cover it up and see if you still have it...

Oh btw, what nutes are you using? I use GH 3 part.

Thank you everyone. I treated the problem with panhead's instructions as if it were powdery mildew just to be on the safe side and added a couple more fans to the grow room so everything is looking great again. I also covered the pots up with some styrofoam lids. Pazuzu, I also thought that it might be salt residue but my other hydroponic plant (GHS "The Church") doesn't seem to have any of the white substance on the rockwool so I doubt it. And yeah I'm also using GH Flora series nutes.

potgrower123 said:

Thank you everyone. I treated the problem with panhead's instructions as if it were powdery mildew just to be on the safe side and added a couple more fans to the grow room so everything is looking great again. I also covered the pots up with some styrofoam lids. Pazuzu, I also thought that it might be salt residue but my other hydroponic plant (GHS "The Church") doesn't seem to have any of the white substance on the rockwool so I doubt it. And yeah I'm also using GH Flora series nutes.

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I still believe that it is built up salt residue..i use GH Flora Nova and noticed the same thing on all of mine, just not to the extreme of yours....