Im officially stumped! P deficiency help!

[smurfin'herb]

I never come here to ask about plant problems cause ive got em down pretty good, but i just cant figure this one out pls help!

Ok so I have some plants in 3gal bags of coco. They are about 2-3 ft tall (very bushy) and have been vegging for bout 6-8 weeks. About 7-10 days ago i started noticing Phosphorous deficiency. So I checked the runoff just to make sure there wasnt to many salts that had built up and cause lockout. The runoff was 350ppm and 5.6ph so i was like "well obviuosly they need food". But i was kind of shocked, because usually when my plants want food, the first sign they show is a prominent Nitrogen deficiency.

So i fed them the 6/9 gh flora series coco formula (heads), and it gave me like 850ppm or somethin. I then added 1tsp of cal mag because it is coco after all, and i am using r/o water. I also use humic,fulvic,carbs,microbes,silica,h-zyme and vitamins all at half strength. So the result ppm of the final mix was like 1250. I would think this would be an optimal range for such large plants. But then again, i never grow plants this large indoors and dont have much exp when it comes to feeding them.

So here i am, i fed them that mix 3 days ago, and leaves are still getting blotchy, weak, droop/hang, and then fall off. Its all happening at the bottom of the plants, obvious sign of mobile element. Plus i know this is a P def for sure (im not a noob), i just dont know whats causing it.

What do you think the problem is?
Do you think im not feeding enough?

 

[bombadil.360]

r u root-bound by any chance? watering too much?

 

[greentrich]

If your temps and RH are good, sounds to me like something else is locking it out. Could you have OD'd on another nute that would displace your P?

Just a thought.

Could root aphids be a possibility??? Not that I want to scare you with that. But I was just reading the thread on that and the OP's description of his symptoms was that it looked like either some type of nute lockout or PH issue, then he finally diagnosed it down to root aphids.
Thinking out loud here.

 

[smurfin'herb]

not rootbound, water every 3 days.

temps fine, rh is about 70%.
I have noticed a few fungus gnats flying round when i water, but after looking in the coco, i didnt notice any larvae hopping/crawling around so i think im good. But ill check into the root aphid thing..

 

[Norkali]

Could root aphids be a possibility??? Not that I want to scare you with that. But I was just reading the thread on that and the OP's description of his symptoms was that it looked like either some type of nute lockout or PH issue, then he finally diagnosed it down to root aphids.
Thinking out loud here.

That's what I thought...take a careful look at the top of your medium, disturb a little bit with either a tool or your finger, look for VERY tiny whitish, almost-clear bugs crawling around. Hope to your deity that you don't find any! Either way, it would be a good idea and good garden practice to get on top of those fungus gnats as soon as possible too.

If you are root aphid free, I would personally look into pH (5.6 sounds a bit low, eh? I thought you shot for 5.8-5.9? Soil guy here...) How about light levels? Is the lower part of the plant receiving proper amounts of light? I've had lower portion of plants show deficiencies and die off from what I believed to be not enough light...especially when portions that were then exposed to more light recovered...

 

[smurfin'herb]

It could be the light issue. Its a 4x8 with 25 2.5foot plants with 600watt mh on a mover.
Also could be carbonate build up or nutrient imbalance. I could have just simply added incorrect ratios of micro and grow. Aslo Ca and Mg like to acculmulate and become offsett in ratio and unavailiable in coco sometimes. Im pulling my hair out. Even tho the ppm is super low, im still gonna flush a few and see if i can get a recovery. Ill let ya know what critters i find if any!

 

[smurfin'herb]

I wish i had a camera on my 30x scope! I found lots of little goldish brown crawlies roaming around in my pots. I could see them with the naked eye, but couldnt make out what they looked like exactly. This is the culprit! Im sorry to say that i think its red assed root aphids.

 

[Norkali]

Ouch...between you and me....Pyganic II (5%) along with Azatrol - reserve the use of imid/bayer for after those don't work.

 

[greentrich]

I wish i had a camera on my 30x scope! I found lots of little goldish brown crawlies roaming around in my pots. I could see them with the naked eye, but couldnt make out what they looked like exactly. This is the culprit! Im sorry to say that i think its red assed root aphids.

That really bites Smurf. I'm almost sorry I brought it up, but glad you found your problem. I read that thread and it scared the shit out of me so much I pulled a couple plants out to see if it was causing a couple issues I had a while back. I got lucky.

I am curious about a solution if I ever have the unfortunate luck to be visited by them. So please let us know how things go for you and what the solution was.

Good luck!!

 

[hazy]

low pH can cause P defs. 5.6 seems too low for coco. Bugs eating your roots could cause your pH to drop too.

 

[smurfin'herb]

Hit them with spinosad, and the rate of damage to the plants decreased by about 50% or more. Its been 5 days and i saw some more crawling around, so i just used up the rest of my neem oil at 1/2 tsp/gal and watered it into the coco while crossing my fingers at the same time. The plants will be outside in the ground soon, so im hoping that just by being outside, mother nature will correct the problem. It already will have a good head start since i have taken out most of the critter population in my coco! I feel bad for the little guys that survive tho, they are gonna have some serious competition here in a short while. lol. Its like putting a domestic dog into the middle of the jungle. They are gonna be toast!

 

[Xtensity]

70% humidity is pretty high....

If there's fungus gnats flying around the room when you water, I personally would take caution to that; take some steps to prevent possible damage if you think there is none, atleast until they disappear from your room.