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small brown spots on older growth-only on veins


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Hi there,

I have some small brown spots about the size of a pinhead on some of the lower growth on only 1 of my girls. Plants are in 50/50 potting mix/perlite & have been supplemented with hydro veg nutes.

 

Plants are growing horizontally. The spots have appeared in the last 48 - 72hrs on the lower areas of the secondary growth. This secondary growth has just recently started to fill out as Ive switched to 12/12 about a week ago.

Im still using veg nutes(waiting for payday!!) ;)

 

I have checked closely with a 6x magnifier & there are no pests on underside of leaves or elsewhere. :o

 

I have also read some nutrient defiency info on this site & others.

 

According to what Ive read it could be :-

-a Magnesium defiency,

-or calcium toxicity which produces magnesium defiencies,

-or an Iron toxicity,

-a Manganese defiency which gets locked out due to high pH and when

-theres too much Iron,

-a Boron defiency.

 

I flushed all 3 plants this morning by drilling small holes around top of pots and sitting them in lukewarm water in the laundry sink adjusted to pH 6.5 for about 10 mins then draining. The draining water was slightly coloured yellow but not much, although its hard to detect colour change in a stainless steel sink!! lol

I figure I wont feed them for about 2-3 days then Ill have some cash to switch to bloom nutes supplements. :o

 

If anyone has experienced this problem, I could really use some advice!!! ;)

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If you are using a good quality brand of nutrients then you should not be experiencing any deficiencies, which brand are you using? Are the effected leaves in the shade or exposed to full light? Are you foliar spraying or have you noticed any little insects around?

 

lol

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Hey Tom,

Im using R&D aquaponics General Purpose hydroponic nutrient-total grow. In tems of grams/litre it is 23/9/17.5 (N/P/K) with added Calcium, Magnesium, Sulphur, Boron, Cobalt, Copper, Iron, Molybdenum, Zinc< Manganese & Aluminium.

So I guess that rules out the Magnesium, Manganese & Boron defiencies.

I am mixing the nute to the minimum strength 5mL/Litre pH adjusted water.

 

I was thinking the same thing - adding nutrients I shouldnt have any defiencies, so perhaps the soil pH had risen or dropped. Do you know which way potting mix usually goes -up/down?

Atm I only have a liquid pH colour test kit so only the water gets adjusted to approx pH 6.5 before I add the nutrients.

 

I checked again this arvo for any pests with a 6x magnifier. Couldnt see anything.

 

The effected leaves are towards the bottom and partly/mostly shaded.

 

I havent foliar sprayed for almost a week. The last foliar spray was La Femme on tuesday. According to the directions it should be foliar sprayed twice, a week apart. So on tuesday its due for another spray.

 

Im starting to wonder if the foliar spray caused it - maybe I shouldnt give it the second spray as all 3 plants have showed no signs of hermie as yet(fingers crossed!) :mellow:

Edited by rosscopico0
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Im using R&D aquaponics General Purpose hydroponic nutrient-total grow. In tems of grams/litre it is 23/9/17.5

Buy some mj specific nutrients, most hydro shops sell them, we are using Dutch Master two part and find them very good.

Atm I only have a liquid pH colour test kit so only the water gets adjusted to approx pH 6.5 before I add the nutrients.
Add the nutrients first and then test, the nutrient colour is just about unnoticeable in such small amounts.
The effected leaves are towards the bottom and partly/mostly shaded.
Do the spots smear if you rub them, are they on the surface or is it the leaf itself that is going brown?
Im starting to wonder if the foliar spray caused it
This is also a possibility as you have to really drench the plants with La Femme, it could be residue from that.

 

lol

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Hey Tom,

Planning on getting some cannabis specific flowering nutes this week.

I pH tested my veg nute solution and its sitting at 6.5.

 

I tried to smear the brown spots to no avail. So its the leaf itself that is going brown.

The affected leaves are developing a yellow tinge around the brown spots.

On the lower of the leaves affected, the spots are getting larger.

 

But since there is no yellowing at the tips of affected leaves, Im inclined to think that it isnt a Nitrogen defiency. Could be wrong though as this is my first grow and the only knowledge I have is from reading.

 

I would tend to doubt that it is a residue from La Femme, since it is only affecting 1 plant. The other 2 are fine. The affected plant is also the smallest of the 3.

 

Since I flushed them yesterday, I wondering if its too soon to add nutes to them. Dont want the root zone too wet. Suggestions??

 

EDIT- just noticed this afternoon that there are a few small flying black bugs in with my plants. Do you think these little buggers may have caused the problem? - although I would tend to think this is not the case as only one plant is affected.

Edited by rosscopico0
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I would say that it is probably due to the plant using up the leaves as they are no longer receiving enough light, normal enough if this is the case.

 

just noticed this afternoon that there are a few small flying black bugs in with my plants. Do you think these little buggers may have caused the problem? - although I would tend to think this is not the case as only one plant is affected.
This sounds like it could be scarid fly/fungus nat and is a problem that would need addressing asap as the larvae attack the protective coating on the root system and leave the plant open to root rot.

 

lol

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Scarid flies are a tricky problem, the strips I describe in the "Prevention" link in my signature would help, read through the topic though as the brand name changes, the active ingredient is the thing to look for. You could also get some sticky flytraps and take the insects that stick to it to a good garden or hydro shop and see what they say they are (positive ID) and what to do about them now that scarid fly drench is no longer available.

 

Other members may have a suggestion or two as well.

 

lol

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Hey Tom,

I got some pyrethrum spray with garlic today.

Did a test run on some basil I found to be infested. The little buggers f***ed off, hopefully they wont return!!

Thinking Ill probably do another spray in about a week.

After spraying basil, I sprayed the only mj plant with the brown spots - gave it a good soaking.

Figured Id only do the one in case the spray kills it!!

Ill let youse know how it went in a week or two.

Thanks for your help Tom

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