Symptoms are spreading

So I am seeing more and more leaves affected by this “spots” it’s mostly the upper part of the plant and a few sugar leaves are showing signs also
@garrigan62 Ive seen your comments on other threads with similar issues and was wondering if you could take a look also and tell me what you think.

ILGM white widow

Coco/perlite 5 gal fabric pots

PH of runoff : 5.9

What is strength of nutrient mix? Ph perfect for coco. 1/2 oz A&B bloom, 1/4 oz big bud
@ 1200 ppm


2 - 600 HPS & 1 900w LED (426w actual)

Temps; 79-80 day. / 75 night

Humidity; Day 43 / night 52

Ventilation system; Yes, 6” exhaust/ 4” intake for heat, 4” exhaust 4” intake for humidity

AC, Humidifier, De-humidifer : no

Co2 : no

I’m also seeing an increase in fan leaf stems turning red/purple

This sure looks like " WHITE POWDERY MILDEW ’ what has been your humidity and have you ventured to nere by woods at all ? The reason I ask because you could have brought it in with you if you did…
And will this white stuff rub off using your fingers ?

Here is why I say what i’em say sir


What causes White Powdery Mildew?

High Humidity

WPM needs moisture to thrive, but that doesn’t necessarily mean it needs water.
Having a grow area with
high humidity is all WPM needs to grow. This seems to be a bit problematic since
young cannabis plants
grow best in relatively humid environments (40% -60% RH). Luckily, high humidity
usually only becomes an
issue when it’s combined with the next cause (low/no airflow).

People who live in environments with extremely high humidity (such as Florida
and the UK) can purchase a
dehumidifier to control humidity in the grow area. This is especially important
during the flowering phase
when humidity needs to be much lower (45% rh) to prevent rampant growth of WPM
and bud mold.

Low/No Airflow

White Powdery Mildew has a hard time settling in a grow room where the air is
being moved. High humidity
will give WPM the conditions it needs to survive, but poor airflow is what gives
it the ability to settle
down in the first place. In fact, a small (preferably oscillating) fan moving air
in a grow area will prevent
the vast majority of White Powdery Mildew woes.

Poor Ventilation

If you have WPM spores in your grow area and the air in grow area is never
exchanged for fresh air, the
spores get multiple chances to land on your plants and reproduce. This happens
most often in conditions
where cannabis is being grown in a closed, unventilated space - such as a closet -
and precautions aren’t
taken to exchange old stale air for new fresh air.

Leaf-Leaf Contact

Leaf to leaf contact = moisture = White Powdery Mildew!Leaves that are touching
each other will form
moisture between them, and thus they become more likely to contract WPM. Untrained
bushy/leafy plants
with lots of new vegetative growth are especially prone since plants will often have
leaves mashed up
against each other as they try to reach the light.

Advanced growers can defoliate some of the fan leaves that are completely shaded
from the grow light
to make fewer choice landing spots for White Powdery Mildew. Also, defoliation
frees up energy for the
plant to use when done correctly and increases yields! See our article on
defoliation for more info.

White powdery mold on the stem of an outdoor plant - White powdery mold can
grow nearly anywhere on the
plant that’s exposed to air.

How to Eliminate White Powdery Mildew

As I mentioned earlier, I recently had a battle with White Powdery Mildew. Rather,
it might have been a
battle if I noticed it later or waited to fix the problem. That’s the one good
hing about WPM: in most
cases when WPM is caught early, you can remove all traces of the mildew without
harming your plants.

There are quite a few products and homemade concoctions people use to treat WPM.
Among the effective treatments are:

Milk (1:9 ratio of milk to water)

Baking soda (2 tablespoons per gallon of water)

Neem Oil (4 teaspoons per gallon of water)

Hydrogen Peroxide (1 teaspoon per gallon of 35% H202)

SM-90 (1:5 ratio of SM-90 to water)

Rather than go into these methods, I’m going to give you the simple strategy I use
that gets rid of White
Powdery Mildew on the first try, every time! Here’s my trusted 3-Step White Powdery
Mold cure:

1.White Powdery Mold: Ruiner of beautiful plants.Remove White Powdery Mildew from leaves -
Get some water
(tap water works fine) and some paper towels. Wet the paper towels and use them to g
ently wipe the mildew
off the affected leaves whilst being careful not to jostle any leaves with spores on
them. Using a wet cloth
will ensure that more spores stick to the cloth instead of becoming airborne. Note:
While it isn’t necessary
to use paper towels, their disposability helps to curb the spread of spores from one
leaf to another.

2.Ensure plants have proper airflow and ventilation - Even if you have absolutely no
airflow or ventilation
in your grow room, having even two fans will drastically reduce your chances of
encountering WPM while also
benefitting your plants overall health. One fan should be oscillating if possible
and should gently blow air
over your plants. All the plants need is enough air to gently rustle their leaves.
The second fan should be
in your grow room pointing outward, pulling heat away from your plants (only needed
if you have no ventilation).
Having a fan pointing out of your grow room will force old air out of the room, and
in turn, pull new air into
the room. At this point, you’ll have new air coming in, being used and circulated,
then kicked out. Keep in mind
that two fans is a minimum.

3.Treat plant with SM90 to kill spores prevent future growth - Mix 1 part SM90 to 5
parts water(I’ve found 7 parts
water to be equally effective) in a clean sprayer/mister. Wait until just before your
lights for off for the day
and mist your (newly cleaned) plants. Get all the leaves! This diluted SM90 mixed will
kill any spores it touches,
and anywhere it lands becomes uninhabitable for future spores. Plus, it’s safe to use -
even during flowering - and
it smells awesome.

There you have it. If you end up running into White Powdery Mildew, give this advice a
shot and you won’t have to
deal with it past that first day. If you do end up using these steps, feel free to
let us know if it helped you or
not, or how you did it differently. When growers know just a little bit about this
disease, it doesn’t have a chance!

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Humidity has been about 43-47% during lights on and about 52% during lights out. Temps are about 80 during lights on and 75 during lights off. Have a 16” oscillating fan on them 24/7. These spots are brown/ copper color. I’ve tried to wipe the leaves and there’s no change in the spots .

Same pic without the flash on

The discoloration in the margins is a light green/ yellowish color

Have you used a loupe and checked the under side of the leaf for mites? That’s how mine looked with the spots almost like mildew and some looked like calcium deficiency but it was definitely spider mites.

I haven’t seen any evidence of mites yet. Undersides of leaves are clean no eggs or droppings that I have found . I do the paper trick once a week ( white piece of paper under different areas of the plant and gently shake then smear any dots looking for blood) and no webbings

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I never seen webbing. They were mainly on my smaller lower leaves. Ok just a thought. You say it’s spreading so is this happening on upper leaves as well?

I have two sugar leaves tha have been affected @Jbum

And quite a few mid fan leaves that have browned crispy edges with red/brown spots and the beginning of discoloration in the margins (the white is the flash reflecting off the leaves)

Check this out @Watt-Sun see if this may help you identify. Your in front of the plant so you can tell way better than a pic can show.

It looks like nute burn on the tips.

Deficiencies with pics, descriptions and remedies

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The edges look like potassium and the spots look like calcium deficiencies. I’m using a complete nutrient line specifically for coco so that’s why I’m not sure what’s going on. Technically I shouldn’t be seeing any deficiencies. @Jbum

@Watt-Sun Does the line your using have a cal/Mag supplement?

And how old again? Any new growth if so how does that look?

It’s the advanced nutrient ph perfect line for coco. You aren’t suppose to need to use any cal/mag.

76 days old
32 days into flower
Yes the buds are making plenty of new sugar leaves and except for those 2 the seem dark green but healthy

Little nute burn going on perhaps a bit of nitrogen tox? That dark green could be a sign of that. Not a pro here by all means just trying to eliminate possibilities with ya.


Yeah i want to back off the nitrogen but the nute line I’m using is an A&B style . A is a 4-0-0 but has all the calcium and mag , iron etc. In it. So if I cut that back I also lose out on them .

To me they look fine.
Your Half way into flower…expect to see more yellowing, spots and the like as you get closer to harvest. You don’t want them to stay picture perfect. They will naturally draw from older leaves nutes needed elsewhere. If that’s all that’s showing as far as spots etc I say no worries.

My thoughts anyway


This a normal amount of leaves that drop? I get this much about every other day . Each pile is from different plants.

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I don’t see a thing wrong. You are probably at the upper end of the tolerance of the plant for the nute load you have; you could bring that down to around 1,000 ppm with no ill effects. You are going to start seeing some deficiencies but I like keeping the plant green as long as possible. Those green leaves are making sugar for flower production.

Coco requires periodic flushing and I think I would dose it with a 1/2 strength dose of cal mag as coco does tend to sequester calcium. This can cause other issues and they can magnify over time.

Plant looks great overall.