White spots help!

Hi grower fellas, it is Grapefruit in coco coir 60/40, 22litres pots, still on veg. Any one knows what are those white spots? Plants stoped growing, they look fine and happy normaly consuming water and sudenly they just stoped stretching. I have another room and i didnt found any white spots on those plants. First i thought maybe it’s left overs from foliar spray but only this room has those spots. It scrubs off. Any desease or something?

Could this be mildew?

It does look a bit like powdery mildew. If it was residue from a foliar spray I would have expected a coffee ring style mark (more concentrated around the outter perimeter of where a drop would have been located). One of the photos looks circular but expanding out from the center (pic 3 of 7). What's your humidity like? You have a fan blowing on your canopy?

Yea, it looks like powdery mildew . I'd consider hitting it with UV.

Attikus112 said:

It does look a bit like powdery mildew. If it was residue from a foliar spray I would have expected a coffee ring style mark (more concentrated around the outter perimeter of where a drop would have been located). One of the photos looks circular but expanding out from the center (pic 3 of 7). What's your humidity like? You have a fan blowing on your canopy?

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Between 40~60%. Yeah i have 5 fans. It was werry hot weather for about 3 days outside was +33 in celcius. They were sleeping in +26~30 celcius. How to get rid of mildew? Some one told me baking soda or something could help?

budau said:

Yea, it looks like powdery mildew . I'd consider hitting it with UV.

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What do you mean?

Can't see very well because of the dark/high contrast on the leaf shots, but almost looks like spider mites?

GodFather777 said:

What do you mean?

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Hit your plants with UV light at night. UV light is what will kill powdery mildew. Unfortunately the fungus spores are in the environment. I've never personally had it but I have known others who have, nothing else has worked other than UV. The only sure way to clear the spores in your environment would be to use something like Ozone. Might be worth considering a fungicide as well.

ColoradoHighGrower said:

Can't see very well because of the dark/high contrast on the leaf shots, but almost looks like spider mites?

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If it were spider mites the tell tale signs are speckled dots on the tops of the leaves where they're underneath chowing down. They also start webbing from underneath. Easy way to tell is to flip the leaves over, you can see the adults without a microscope.

I use potassium bicarbonate for PM on my squash plants, I heard that sodium bicarbonate (baking soda) works but might not be as effective. I've never used it on cannabis plants though. I guess it probably no worse than an epsom foliar feed, probably could only use it in veg though.

Damn, that's definitely PM! I've had that before, real nasty and I've never gotten rid of it when it hits, only really controlled it enough to harvest and wash my buds in peroxide. There are many solutions out there, I use peroxide diluted right down. Spray in low light, cool weather every couple of days. Remove fan leaves that are worst affected to minimize the damage. And before you start a new grow you are going to want to deep clean the grow area and tools.

Thanks for solutions guys! If any one knows anything else how to get rid of it, apreciate that info ill try what i can. Thanks again!

budau said:

Hit your plants with UV light at night. UV light is what will kill powdery mildew. Unfortunately the fungus spores are in the environment. I've never personally had it but I have known others who have, nothing else has worked other than UV. The only sure way to clear the spores in your environment would be to use something like Ozone. Might be worth considering a fungicide as well.

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I found a lot of different lamps and pricing, maybe you could recommend something particular? Maybe some one who already used thos metod could recommend something particular?