Seedling worm / bug attack, what is it?

Hey everyone, hope the sun is shining wherever you are.

So I recently started some pretty old beans from Bodhi Seeds. A few Tigers Milk, my last Goji and some newer Spirit Train. They were started in a mix of brand new bags of black gold and happy frog soil. (I often do paper towel method but figure this is more natural and seems to work fine in nature and for everyone else).

Happy to see that a few of the tigers milk and goji have sprouted and come up from the soil, until this morning when one of the once was happy seedlings was limp in the pot this morning and another looks like it may be on the way out.

Having dealt with dampening off before I thought it was odd and not what I was experiencing, so I pulled the wilted / dying seedling out of the dirt to find these black headed or butted worms on the taproot of the seedling.

Anyone ever experienced this, know what these dang things are, or have thoughts to keep this from happening in the future?

As of now its looking like I should have a couple goji and a couple tigers milk still that I am hoping are getting big enough that they will be fine.

Thanks in advance.


Fungus gnat larvae - Bti, nematodes, h. miles. :v:


Thank you @PlantShepherd

Seems impossible to get soil these days without them. Is there something people do to pre treat their soil prior to starting seeds directly in the dirt to avoid them killing their precious seedlings?


Sorry for your loss :disappointed:, you can flush with diluted peroxide, but that will kill also the microbes (the good and the bad angeldevil|nullxnull ) so you will have to repopulate them later on with some sort of tea or equivalent … icon_e_confused|nullxnull


I can’t really speak on that as I haven’t tried. I would assume you could treat the soil ahead of time and then add your seeds/seedlings. :v:


Solarize it by putting it in a clear trash bag and leaving it out in the sun for 6-8 weeks or put in the oven 3" deep at 200 degrees until the center of the soil reaches 180.
Too bad you had this issue. They’re selling recycled soil out your way or what? This is common now? Anytime I’ve had issues with bad soil it was always due to a rip in the bag letting water in. Never had pests lying in wait though, I dont think…( or did I ???)
Perhaps letting the soil thoroughly dry out for a week or two in advance would help. Fungus gnats like that moisture. I never actually saw their larvae in person. Just the adults. But they like that soil that stays moist all the time.
You can sprinkle diatomaceous earth on top of the soil, to kill larvae , and you can also put a layer of sand on the top of the soil, I think a half of an inch was recommended, which they don’t like to dig through to lay their eggs. That’s supposed to work very well for control.


@PlantShepherd @George1961 @Upstate

Thanks for the replies everyone. I took off into the wonderful mountains today until almost dark. Life is good.

Yeah I am sorry for the loss but hey life is moving forward and there is only learning to be done… and thankfully there are some survivors… (maybe a male and female Goji? por favor)

In all reality, I am happy that I am getting germination on the Goji. They were one of the first seeds I ever ordered, all the way from Attitude Seeds and have been through moving, stored out of and now in the fridge.

Im up in Washington and I am not sure what the hell they are selling… I use Canna Coco for my drain to waste, and have been getting a bunch of fungus gnats from them in my flowering room lately. Not sure what coco everyone else is using, but I have heard of gnats in coco.

The bags of black gold and happy frog were literally opened, mixed together, and then planted the seeds and I haven’ tnoticed any fungus gnats except in my flowering room and my veg area is in a totally different area / room.

Who knows… I would still like to hopefully stick with planting directly into the soil and skipping the paper towel if I can.


Pre-treat your medium with Gnatrol to prevent fungus gnat larvae.
Gnatrol Label

Scroll down to section 9.0 for application directions.


I’ve read that the larvae could kill seedlings, first I’ve seen it, sorry for your loss.

My take is the same as @buzzmobile said except I used ground up mosquito dunks.
About 0.2 gm worked into the top inch of soil per 5 gal pot worked like a charm for me. Plan on re-dosing every 10 to 14 days as the BTi does not seem to persist in the soil on its own.
My variation on @Upstate is I buy 6 mo. ahead and let the bags ‘age’ in the garage, summer cooks them and winter freezes them. That gets about 95% of gnates and the very few that manage to survive that are super weak and feeble & diatomaceous earth is great too.



I went to Gnatrol over the ground up mosquito dunks and mosquito bits that I had been using. I had a bad infestation that the dunks were not controlling. The Gnatrol was very effective after two treatments spaced a week apart.

Put up some yellow sticky traps to monitor the fungus gnat population. If there is one on the card it is time to start treatments. The fungus gnat larvae will also eat root hairs forming on freshly stuck cuttings. Soap spray will kill adults if you hit them with it.


Thanks again - have to go ahead and get some Gnatrol and give it a try next time for sure.

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That’s a very good idea. If next year is at all like this year, with everyone planting a garden, its imperative to buy in advance. So much stuff was out of stock most of the season, so if you see it, grab it.



Isn’t the truth! I ended up with 1700w of flowering and no trellis netting available at any of the stores around me, where I can typically just run in and pick it up… caused a bit of a headache hah