Nematode warfare… Karma: 1 — Sciaridae: 0

Yesterday I treated the entire apartment, well that was an overstatement, I treated all the flower pots, orchid pots and vivariums at least with nematodes. Waging war on the Sciaridae. I have not really seen any of them around the apartment, but they absolutely love my nano-vivarium and my flaskbaby nurseries (mini-greenhouses) where it is nice and warm and humid. But I took no chances and treated everything with the tiny biological predators, the nematodes (from Lindesro). It is not as disgusting as it sound, you have larger creatures living in your bed or favorite pillow… namely bedbugs. Anyway, they are harmless to humans and pets and it is nice not having to use any toxic poisons to combat these darn things that have invaded my 35×100 cm slice of tropical heaven (the nano)! 

Drosophila melanogasterSciara hemerobioidesMost people think all the tiny flies we often see around our plants are the common fruit fly (Drosophila melanogaster), and of course – some are. These are however merely a nuisance but harmless to our plants. But there is another pest from the Sciaridae family called Sciara hemerobioides, or the dark-winged fungus gnat (or “sorgmyggor”/”sorrow mosquitoes” as we call them in Swedish – very appropriate name). These evil doers look a lot like the common fruit fly, but are not only a nuisance their larva love to munch on fine tender roots. Although most orchid roots are too thick to be bothered, these larvae can completely decimate a cultivation of fine moss or young plants – such as my tropical moss and flask babies.

You can tell the flies apart (without putting them under the microscope) by the way they fly. The evil fly is not a very skilled flyer, Sciaridae moves in a jerky fashion and is often seen running over the surface rather than flying. They are also not attracted to fruit or wine like the harmless fruit fly so you cannot trap them in this way. They are however attracted to yellow, so I hung yellow fly traps (the yellow cards with glue on them) to catch the adults, then sent in the nematodes (Entonem /Steinernema feltiae) to kill the next generation larvae.

It all took about 2 hours using the high-pressure watering hose (at low pressure) but it is well worth if it only works. Now I just have to sit back and wait. They say it may take 2-3 weeks before you see a noticeable difference, but since I ordered large yellow fly traps at the same time it already feels better. Now I only see one or two flying around in the nano-viv  and 50+ stuck on the yellow card – nice! Too bad that they already managed to consume about half of the nice tropical moss I had growing on the EpiWeb back wall… but it will grow back.

My fingers and toes are crossed, and I am prepared to take on round 2 if needed. This is war!!
(Lovely fly images courtesy of Wikipedia)

By | 2017-10-13T11:26:15+02:00 March 16th, 2009|Categories: A day in the life of...|Tags: , , , , , , |18 Comments

About the Author:

Karma is a digital nomad graphic artist and writer, orchid nerd and long-distance hiker from Gothenburg, Sweden. Former editor-in-chief for the Swedish Orchid Society magazine, published internationally and held lectures on orchid culture.


  1. […] I am looking for other alternatives first. Since the killer nematodes did such a great job on the fungus gnat problem (Sciaridae) I had last winter, I decided to apply a tiny army of killer mites to go after the spider […]

  2. gillt September 24, 2009 at 20:48 - Reply

    Excellent post! I have an epiweb with moss growing on it…now I have gnats. I also have a ceramic tube for orchids that is now infested. I didn’t know they eat moss, but now that I think about it, my moss does seem to be on the retreat. I’m going to go straight out after work and buy some “bacillus thuringus,” a nematode fungus gnat killer. Does it compare to Steinernema? Anyway, how do you apply the nematodes to the epiweb surface…a mister?



  3. Karma September 25, 2009 at 08:27 - Reply

    Hi Tony! I am glad to hear that you had some use of my eperience with the fungus gnats. They don’t do much damage to orchids, but like you have seen they like to chomp on the fine roots of the beautiful mosses in our vivariums. In mine they cleaned off a big patch on the back wall, not pretty. I have no idea how “bacillus thuringus” compares to the nematodes I used, but if they say they go after the gnats it is definitely worth a shot. “Steinernema feltiae” did a great job on mine. I still have a few fliers buzzing around, but the infestation is definitely gone. I suppose I could do a second cure of nematodes, but I just keep after these lone flyers with the yellow stickie papers now. I highly recommend having those up all the time for maintenance. My nematodes came in a soft clay that was to be mixed into 10 liters of water then watered in the media or misted on the EpiWeb walls. I used a high pressure prayer for this (on the lowest pressure I could set it to not to hurt the little guys). It was easy to do. Good luck with your nematode warefare. I love science/biology!!

  4. gillt September 25, 2009 at 16:58 - Reply

    I’m a molecular biologist

    Anyway, Bacillus thuringus (Bt) which is the engineered microbe they use for Bt Cotton and Bt Corn here in the states is a bacteria that comes in different strains. Bt Israeli is designed for fungus gnats. Nematodes are more labor intensive to grow up, so I hope this bacterium does the trick. You can use it straight form the bottle.

    I currently have a nano-viv with a ceramic tube and an epi-web wrapped cylinder like the one Mikael has here

    Both are a few months old and both have local mosses growing on them along with a few miniature orchids.

    Great website by the way.

  5. Karma September 28, 2009 at 08:53 - Reply

    I am happy to hear you like my blog, thanks a lot! Wow, a molecular biologist… cool. Sounds like you might know what you are doing. I would love to hear how it works out with your gnats. The EpiWeb cylinder looks cool. I had a ceramic cylinder in my nano-viv at first but did not think it worked very well. I did not think it let out enough water through the clay, at least not the pipe that I had. I replaced mine with an EpiWeb ILS self watering wall (modified to fit the round interior of the nano) and that worked great! (I had another weird experience with small clay pipes in my warm vivarium recently – I will try to write something about it this week…) I sold my nano this spring though – want to get a larger vivarium with the whole rainforest setup eventually. But that is a big project that is going to have to wait. Unless I win the lottery. 🙂

  6. gillt September 28, 2009 at 14:58 - Reply

    Ha, my clay pipe actually seeps too much and water overflows the base. Good luck with the lottery!

  7. Karma September 28, 2009 at 17:54 - Reply

    Thanks Tony! This is what I am dreaming of…I am accepting donations, lol.

  8. gillt September 28, 2009 at 21:05 - Reply

    That is definitely the next logical step in your orchid growing quest.

    The US is so far behind offering anything like this in the hobby. Also, that setup seems to have two different lighting options. LED/Halide combo and Fluorescent tubes. Is that right? I’ve had limited success with LEDs, and good success with halides and CFL bulbs in growing local moss varieties.

  9. Karma September 29, 2009 at 18:57 - Reply

    Yes I know… once you have seen this it is really hard to settle for anything else. This company is actually just one guy who makes these great vivariums to order. Really neat stuff. I am interested in the cool vivarium for Pleurothallids. This one comes with cooling, climate control, and 5 T5 54W light fixtures (grow lights), plus 4 35W halogen spots (mood lighting). This viv is also complete with watering system and both back wall and bottom clad in EpiWeb. A dream! I think they cost about 20 000 kronor ($3000 us). Not bad for what ýou get, but more than I have to spend right now. Especially since I’d have to put a few thousand more worth of plants in it of course! 😉

    No LED’s in this setup. I am not convinced LED technology is there yet when it comes to growing tropicals… I am too quite happy with CFLs, my fixtures in the growing room and warm viv use 55W low energy CFL tubes (x2 per fixture).

  10. gillt October 31, 2009 at 05:31 - Reply

    Update: the BTi knocked back the infestation, with a few stragglers buzzing around. The yellow sticky paper helps.

    I’m using 24 watts of LEDS over my minis right now because my ridiculously over sized (and priced!) 125 watt CFL bulb burned out unexpectedly. The sickly red color they give off is not aesthetically pleasing though. In short, LEDS are still too expensive and the technology just isn’t there. I’d look to the reef aquarium hobby for break-out technology since over-heating is always a concern for them.

    Hey, this is a bit off topic, but I’m interested in tropical moss for my orchidarium, and availability in the US limited to one distributor who charges about $80 for spores from Mikael. Would you be up for trying to send some over if I cover shipping, and I would be happy to compensate you generously for your trouble? It’s a huge favor, I know, so don’t worry if you can’t do it.

  11. Karma October 31, 2009 at 14:12 - Reply

    Hello again! I am so happy to hear you are getting a handle on the darn gnats! Same result here really. I see 2-3 buzzing around at a time, but the yellow sticky cards really keep them in check. They fill up (eeewwww) in about 6 months and I switch them for new ones. I understand completely what you mean about the aesthetics of the red LED’s… I think sodium lights have similar issues, things don’t look natural and beautiful. What’s the point growing these beauties if we cannot enjoy looking at them while they grow… I am very partial to my CFL daylight bulbs, everything looks natural. An added bonus is that I can use my orchid room for light therapy now during the darker winter months. A lot of Swedes travel to Thailand for the sun this time of year, or just get depressed when the light disappears for so long. But not me. I think my growing lights are helping a lot.

    I don’t mind helping you get a hold of some tropical moss. The one I get get is a finely ground and dried mix (consisting of sphagnum, and 3-5 different kinds of tropical moss). All you do is to add water and smear it onto the surface you want to cover in moss. Then wait… and wait… it takes a while. They sell them by 50 gram bags, and a bag cover about 0.5 sq. meters (130 SEK/bag). Hmmm customs will probably get a kick out of these baggies… but what the hell. Email me with the details and I will send you some moss.

  12. Layna November 23, 2009 at 05:23 - Reply

    I am wondering if you have animals living in your vivarium. I have a large tank with Whites Tree Frogs and am having a terrible time with fungus gnats. Frogs are so sensitive to environmental issues that I don’t want to risk any sort of pesticide. Do you know of anything I might use? Thanks so much

  13. Karma November 23, 2009 at 10:30 - Reply

    Hi Layna. I am sorry to hear that you are having problems with fungus gnats, they are awefully persistent and next to impossible to get rid of completely… I believe that all you can realistically hope for is to keep them under control. I do not have any intentional animals in my vivarium, and I have no experience with frogs sorry. But I hate using poison too unless I have to. Can you ask around in the frog communities, or where you buy your frogs, and see if they are sensitive to nematodes? I think they are more effective than any poison really, and since they are specialized feeders they won’t take out the entire ecosystem at the same time. The ones I used were called Entonem, or Steinernema feltiae in Latin. But there might be others. Those little (and I am talking microscopic) buggers did a fantastic job getting my fungus gnat infestation under control.

    It has been about 6 months since I used them now and I am actually considering doing a second treatment as I have seen an increase in the amount of flying gnats again… @#%?&!! It is nowhere near as bad as it was in March, but my yellow sticky cards (gnat traps) are filling up faster too so maybe it would be a good idea to release another batch of predators to eradicate the colony once more. The yellow sticky traps are the best way to kind of keep things under control in between treatments as it catches the adult fliers while the nematodes go after the eggs and larvae.

    Good luck!!

  14. Layna December 2, 2009 at 01:40 - Reply

    Thanks so much for the info. Someone else had mentioned nematodes but I wasn’t sure what to look for. I will try it right away!

  15. Eduardo Calderon-Saenz November 22, 2011 at 21:53 - Reply

    I have in cultivation (in Colombia) a large unidentified Pleurothallis with tiny but very fragant flowers which are pollinated by (what I think are) Sciaridae. I would like to send pictures of the orchid and the pollinator to you, with the hope you can help me to ID the plant and the pollinator. If you agree, please send e-mail to me.

    Best regards from El Refugio Nature Reservation (Cali-Colombia)

    • Karma November 23, 2011 at 10:53 - Reply

      Hello Eduardo! I am not sure I can ID them for you, but I have friends that might be able to. I will send you an email.

  16. Misha October 17, 2012 at 09:27 - Reply

    I recently rescued a phalaenopsis orchid that had for some obscure reason been planted in humus. *facepalm* Anyway, as I cut the rotten roots, a fungal gnat came to say hi, so I soaked the roots (briefly) in very diluted methylated spirits and dishwashing liquid. Seems to have done the trick to kill them.

    I just thought it might be useful to know, since the gnats (as far as I understand) are your evildoer’s larvae. Still a beginner, though, so feel free to let me know if I’m wrong.

    • Karma October 17, 2012 at 09:33 - Reply

      Interesting idea. I hope it works for you. I have not had a problem with the fungus gnats since I introduced the nematodes, and I keep yellow sticky cards up at all times to catch any strays flying around before they have time to multiply. 🙂

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