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Clear larvae black head burrowing in stem

Dollar

Dollar

Active member
I’ve been growing for 31 years and have seen it all at least that’s what I thought. I have newly rooted clones in 4” coco pots about 2 weeks. A week ago one died, then the next day 2 and every day after a few die each day. These plants are not overwatered or under watered, over fed or under fed. Same mix I’ve been using for years with no issues. Today I broke out the magnifying glass and inspected the roots, stems and leaves of one of the dead plants. At the base of the stem where it meets the coco there are clear larvae with black heads burrowing in the stem. There were many and lots of tunnels. You can tell they’ve been working hard. Keep in mind I could only see these with a magnifying glass that’s how small they are. What are these things and how do I get rid of them?
 
Dollar

Dollar

Active member
TakenByTheSky said:
Fungus gnats larvae
Click to expand...

I don’t have fungus gnats. Not that I’ve seen. I’ve had em plenty of times before and it was clear they were there. The larvae burrow in the stem? Will these fungus larvae kill perfectly healthy plants? I thought they bred in the medium not the stem. Huh? I didn’t know fungus gnats could even kill a plant. Never have before when I had em and I’ve had em pretty bad where they were flying everywhere.
 
buzzmobile

buzzmobile

Well-known member
Veteran
attachment.php


DAMAGE

Adult fungus gnats don’t damage plants or bite people; their presence is primarily considered a nuisance. Larvae, however, when present in large numbers, can damage roots and stunt plant growth, particularly in seedlings and young plants. Significant root damage and even plant death have been observed in interior plantscapes and in houseplants when high populations were associated with moist, organically-rich soil. Thus, a houseplant that is wilting may not indicate a lack of water, but rather root damage by fungus gnat larvae or (more commonly) other causes of unhealthy roots. However, too much or too little water, root decay fungi, and improper soil conditions (e.g., poor drainage, or waterlogging) are much more common causes of wilted plants.

Serious fungus gnat damage is more common in greenhouses, nurseries, and sod farms. Although larvae also feed on plant roots outdoors, they don’t usually cause serious damage.
Click to expand...

Fungus Gnats

I'm surprised that you have not seen adult gnats, but from your description I think TakenByTheSky called it.
 

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Dollar

Dollar

Active member
buzzmobile said:
View Image



Fungus Gnats

I'm surprised that you have not seen adult gnats, but from your description I think TakenByTheSky called it.
Click to expand...

The above pic is exactly what I saw. Thank you! So my question is still can these fungus gnats kill a perfectly healthy plant or do I have another issue? With close inspection daily I notice the plants that eventually die turn darker green, the growth tips stop growing, Lower leaves get yellow spots then leaves slowly wilt over a 24 hour period then the plant dies. I’m thinking now I have another issue other than these fungus gnats larvae I saw. Any suggestions?
 
Dollar

Dollar

Active member
troutman said:
Get some yellow bug stickies. :)
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I do have yellow sticky traps. There’s nothing on em. That’s why I’m here asking. I don’t see anything causing these plants to die. I’ve ripped apart the medium, inspected the roots stems and leaves and everything looks normal except those larvae. The roots look great too. Perfectly white and healthy. I usually troubleshoot issues quickly and remedy the problem cause I’ve had almost every issue there is over the years. This ones got me stumped.
 
T

TakenByTheSky

Sounds like you don't have flyers yet. You need a soil drench to kill the larvae sticking just catch the ones that fly.

Larvae can kill a plant but it's a slow process. My bet is the plant was in sickly shape before hand and the gnat larvae are just quickly making it worse.

Without even seeing things I can say your soil is probably too wet for too long of periods of time and this is the kind of condition larvae thrive in.
 
Dollar

Dollar

Active member
TakenByTheSky said:
Sounds like you don't have flyers yet. You need a soil drench to kill the larvae sticking just catch the ones that fly.

Larvae can kill a plant but it's a slow process. My bet is the plant was in sickly shape before hand and the gnat larvae are just quickly making it worse.

Without even seeing things I can say your soil is probably too wet for too long of periods of time and this is the kind of condition larvae thrive in.
Click to expand...

I’m hearing ya. I do keep the coco quite wet. I’m using the same process I’ve been using for years cloning, transplanting and watering, regular preventive spraying for bugs and pm. I haven’t changed anything. Same gorilla glue I’ve been growing for years without issues. I haven’t brought any new genetics into my grow in 5 years so it isn’t that. All the plants look like they always do perfectly healthy until I notice the issue starting and die within a few days. This is the first time I’ve experienced this in 31 years growing.
 
T

TakenByTheSky

Gnats can come from all sorts of places, sometimes from bags of medium you bring in or even from house plants.

I grow in soil so gnats are always aroubd, they flare up I knock them down with stickies, dry up the soil and eventually they die down.

Very rarely do they kill plants, like I said unhealthy plants always get hit the hardest.
 
E

eyesdownchronic

Active member
Be warned. These have to be a new breed of fungus gnats. I had the exact same thing as you descriped, fungus gant larvae, which I had never seen before, but no fliers, and they took out a large chunk of seedlings, as well as medium sized fully healthy plants. A couple weeks later the fliers appeared in droves. Time to whip out the nematodes before it gets worse.
 
Klompen

Klompen

Active member
I have been having great success with s-methoprene(Mosquito Bombs). I only need a tiny chunk of it left to dissolve in my sprayer bottle and just once a week or whatever I can spray some on the mulch. I had a ton of clones that were failing until I started spraying and like magic they stopped wilting
 
Dollar

Dollar

Active member
Thank you all for the help and suggestions! I’ve had gnats before many times and they’ve never affected the plants just a nuisance to me. Whatever this is its not a regular ole fungus gnat. Perfectly healthy plants die in 2 days. I checked again after reading some replies and not a single gnat in the sticky traps. The picture posted of the larvae is exactly what I saw this morning. I have a sealed grow and I don’t bring in any plants. The only thing I bring in is nutes and coco. After thinking about it only the plants in the latest batch of coco are being affected so that’s not good for others. The plants from the same batch of clones in the previous bags of coco used are fine. At least for the moment. If I was going the nematode route what kind do I need and where do I get em? I’ve never bought nematodes before.
 
Switcher56

Switcher56

Comfortably numb!
Dollar said:
The above pic is exactly what I saw. Thank you! So my question is still can these fungus gnats kill a perfectly healthy plant or do I have another issue? With close inspection daily I notice the plants that eventually die turn darker green, the growth tips stop growing, Lower leaves get yellow spots then leaves slowly wilt over a 24 hour period then the plant dies. I’m thinking now I have another issue other than these fungus gnats larvae I saw. Any suggestions?
Click to expand...

Dollar said:
I do have yellow sticky traps. There’s nothing on em. That’s why I’m here asking. I don’t see anything causing these plants to die. I’ve ripped apart the medium, inspected the roots stems and leaves and everything looks normal except those larvae. The roots look great too. Perfectly white and healthy. I usually troubleshoot issues quickly and remedy the problem cause I’ve had almost every issue there is over the years. This ones got me stumped.
Click to expand...

TakenByTheSky said:
Sounds like you don't have flyers yet. You need a soil drench to kill the larvae sticking just catch the ones that fly.

Larvae can kill a plant but it's a slow process. My bet is the plant was in sickly shape before hand and the gnat larvae are just quickly making it worse.

Without even seeing things I can say your soil is probably too wet for too long of periods of time and this is the kind of condition larvae thrive in.
Click to expand...

Dollar said:
I’m hearing ya. I do keep the coco quite wet. I’m using the same process I’ve been using for years cloning, transplanting and watering, regular preventive spraying for bugs and pm. I haven’t changed anything. Same Original Glue I’ve been growing for years without issues. I haven’t brought any new genetics into my grow in 5 years so it isn’t that. All the plants look like they always do perfectly healthy until I notice the issue starting and die within a few days. This is the first time I’ve experienced this in 31 years growing.
Click to expand...
Well, they do have to eat something, dontcha think? OTOH, wetter than normal doesn't help, but, scratch your brain because that is not the only issue and, I'll lay you dollars to doughnuts it is the present batch of coco you are using is the culprit.
 
T

TakenByTheSky

Nema toads aren't going to wipe them out over night. Your best bet is a soil drench with azamax or neem. Kill the ones in the soil, wait a few days and donut again. Put out stickies for any fliers that pop up, and dry the medium out.

Realistically it could be a bad batch of salty coco that's killing the plants and the gnats are just taking advantage of the situation not the cause of the die off.
 
Dollar

Dollar

Active member
Thank you! I’m thinking you both are right. I’ll check the runoff and see if it’s too hot. I haven’t done that yet. This is the same coco I’ve been using for years. Huh?
 
Dollar

Dollar

Active member
Update - I checked the runoff on the latest plant to die and it was 1900 on .5 scale. Ouch! The ppm of the feed going in was 800. So I checked some of the other plants in that same batch of coco that hadn’t died and they were between 1800-1900. I also checked the plants in the previous batch of coco and it was between 900 - 1000. Obviously the QC department at Mother Earth could use some more stringent checks. Not the fungus gnat larvae causing the issue. Check your coco before losing a bunch of plants like I just did. Thank you all again!
 
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