Spots on leaves

Plant is Bubba Kush, 4 weeks into flower being grown in coco and fed Lucas formula mixed with tap.
Their are no pests around, 100% positive that it's not pest related.
It's mostly on the upper leaves.
The plant itself is absolutely healthy and flowering normally. But I've never seen these spots before so it's really got me perplexed.
Have a look:

Looks hungry. What is your pH?

PH is 5.6
They get fed, drip to waste, every day. I check the pots and they are not overly light come fed time so I know they're getting enough.

We've had that happen on some strains. Unless its happening on more than 50% of foliage, I wouldn't really worry about it too much. pH is 5.8

try bumping to 5.8 at least, might help

LeafLady said:

We've had that happen on some strains. Unless its happening on more than 50% of foliage, I wouldn't really worry about it too much.

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Thats what I figured. the plants are flowering normally, budding up very nicely,

watts said:

try bumping to 5.8 at least, might help

Click to expand...

Am going to do that starting with tonight's feed.

...

Maybe too much water. As said above, 5.8-6.0 pH is best target.

Good Luck. I love Bubba Kush..!

could be the start of ph spots from ph swinging... but not really too sure. 5.8 is deff where you want to be... ilet mine drift form 5.6 6.0

the spots them selves are looking to be the very begining of a K def, or possibly a Ca def, but im thinking a k def...


BUT...not to alarm you...

different forms of PM exist in the plant world as well as different ways that plants exhibit the symptoms...

here is a look:

downy mildew:

Downy mildew is a disease caused by the fungus-like water mould, Pseudoperonospora cubensis, which attacks only cucumbers and related crop species (gourds, squash, pumpkin, melons). This disease primarily affects foliage and can cause severe yield losses in a short period of time.

Symptoms

Symptoms are usually seen first on the lower, older leaves. Initial symptoms of downy mildew typically consist of angular, yellow spots on the upper leaf surfaces (Figure 1).


On the undersides of such spots, a purplish-grey fungal growth may be visible when there is high relative humidity or moist conditions prevail. As the disease progresses, the yellow spots enlarge and become necrotic or brownish in the centre, with the browning spreading to the margins of the spots.



Such spots may merge to form large brown areas on the leaves. Diseased leaves are killed in this manner, if the disease is allowed to develop unchecked. Lack of photosynthetic tissue results in stunting of plants, reduced fruit size and poor fruit set.

Pseudoperonospora cubensis is an obligate parasite requiring living host tissue to survive. It does not live in debris in the soil, and there are no reports of overwintering of the fungus in canada. Occasionally, under optimum environmental conditions, the pathogen may develop thick-walled spores called oospores that are resistant to low temperatures and dry conditions. This is rare and not considered an important source of inoculum. Infections in greenhouses likely originate from another type of spore (sporangia) that enters the facilities from the outside. Local field infections are usually established by spores carried by moist air currents blowing northwards from distant warmer regions where the fungus can overwinter on plant material.

Moisture on the leaf surfaces is necessary for infection to occur. When spores land on a wet leaf surface, they can either germinate and infect through the breathing pores (stomates) on leaves or release many smaller spores, called zoospores, that swim in the film of water on leaves during humid or wet conditions, and enter and infect leaves through stomates. Optimum temperatures for infection range between 16°c and 22°c, with infection occurring more rapidly at the warmer temperatures. The periods of wetness needed for infection on cucumber leaves are about 12 hr at 10°c-15°c, 6 hr at 15°c-19°c, and 2 hr at 20°c. About 4-5 days after infection, new spores are produced and released into the air, primarily in the morning. Spores can quickly spread within the greenhouse via moist air currents, contaminated tools, equipment, fingers and clothing. Fortunately, the spores become less infective under conditions of high temperatures and low humidity in the greenhouse.



and here is another strain; Leveillula taurica:

Figure 2. Light yellow spots may form on the upper side of the leaf corresponding to the powdery mildew colonies on the undersurface of infected pepper leaves.


Figure 2. Light yellow spots may form on the upper side of the leaf corresponding to the powdery mildew colonies on the undersurface of infected pepper leaves.





but like i said my guess is begining of k def or Ca def

pretty hard to get a k def in coco. So maybe Ca.

Ha, joe! I was going to suggest a latent mildew (PM) infection. I am leaning away from a deficiency, myself. As watts says, it's pretty hard to develop a K- in coir, though it can be fairly easy to develop a toxicity, but this does not resemble anything to do with K at this time to my eyes.

Latent mildew infection is my best guess.

have you had the lights on when there were water droplets on the leaves at all?

leaves look pretty dark green so could be an overfert thing going on but you've got the bubba well dialled in so thats unlikely


the only other thing i could think of is whitefly but they are pretty obvious to spot, leaf miner damage has much more defined edges and tends to effect areas between veins.

VG

VG

Thank you everybody for chiming in an trying to help figure this out.
After some careful examination of the plants and some searching around the internet
I am almost 100% certain joe fresh and SeaMaiden are right, it is downey mildew.
Here's a shot of 2 leaves from the same plant;

This ones for you IronLion!

how do you fix downey mildew problem? what do you think caused it?

Hit em with some Safers Sulphur.

watts said:

how do you fix downey mildew problem? what do you think caused it?

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No clue how to fix it or where the mildew came from but it doesn't appear to be getting any worse or spreading to the other plants. Only 2-3 plants have these spots on the upper leaves.
Field&Stream says Safer's Sulfer. I know that sulfer burners are used for PM...

Unless it's the photo, the really really dark green points to Ca deficiency. You may have a fungus too. Good luck. -granger

I believe Actinovate would treat downy mildew well.

I'm not sure that Mildew is what we are seeing.. I DO agree that Mildews sometimes manifest as those kinds of spots.. The spots are sorts of 'scars' that contain, or contained the fungus. Also, look on the stem for a ring of white.

As has been written many times in icmag.com, Mildews are systemic, and get into the system of the plant like the bloodstream.

Some Strains are terrible. Others reisist it sitting right next to it..

In any case, a preventative spray can't hurt.

If it IS Downy or Powdery Mildew, Some things can help the situation:

Keep use of Nitrogen a bit lower, as that makes it worse.

Do watering at the time the lights come on, or soon after - so the plants have a chance to enjoy a Dry Medium by the time the lights go off (which is when Relative Humidity increases).

Indoor, the spraying can be done right before the lights go off, or right after, with a white light on.
Outdoors, spraying should be done in the early morning, after the chill goes away, but the sun is not at a high angle yet. Too close to the heat of th day will cause holes to burn into the leaves - as will spraying with HPS or MH bulbs on..

I recommend outdoors spraying around 8-830am or at the latest 930 am. If it is a marine layer day, or not direct sun, spraying can be done until about 2pm safely. Just don;t let them go to sleep with wet leaves outdoors..!

Safer Garden Fungicide does work, use 20ml a gal. - no more than 25ml. Employing a Wetting agent as well is best. Coco-Wet is a good and cheap one.

Remember, the Safer Garden Fungicide leaves spots that look a touch like Powdery Mildew. - so it can get confusing. If you can, wash off the Safer G Fung after two applications, 8 days apart.

Use plain water at a pH of higher than 7.0 to rinse off the Sulphur. Powdery and Downy hate pH above 7.0. You can go up to 8.o pH on the sprays, and not hurt your plants. That helps in eradication of Mildews...

A friend of mine did :
2 days Safer G Fung + wetting agent
1 day plain water pH 7.0 plus.
repeat this process 3 times, with the tenth day another spray of water to clear out the Stomata.

Don't use milk and make your flowers taste like baby puke. haha... yuk.

Preventative spraying of Safer or a few other products is usually a good idea.

I am going to spray the heinous EAGLE 20, one application, right before flowering starts, in the greenhouse. It is a chemical, for sure, but is reported on other threads on this Highly-Esteemed Website to absolutely eradicate PM. Heated arguments about EAGLE 20, but I live too close to the Ocean to F around.

Lots of Luck.