Fungus Gnats,harmful?

[camillenad]

I've read so many conflicting info on Fungus Gnats. I seem to always have them flying around my orchids, and i detected some small whitish/grey worms which i think are larvae. So, do fungus gnats really harm orchids? or are they just a nuisance to have flying around?

[Leafmite]

I don't know if they are harmful but it isn't pleasant to find them flying around the plants. Drying your orchids a bit between waterings will eliminate them. I have some other plants that can never dry out so I usually have a few. Recently, the new butterwort seems to have eliminated them. Hope someone else can answer your question.
Leafmite

[camillenad]

Thanks Leafmite!

[camille1585]

Yes, they are bad for the orchids, the larvae eat the roots and base of the plant. The larvae are a transparent whitish color with a black head.

I can't tell you what to use to get rid of them (pots need to be soaked in something), being in Europe I'm not familiar with US pest control products.

[camillenad]

Thanks Camille, I got a recipe from Bud on OB made of dish-washing soap, cinnamon extract and water. Will try that one soon, even though i have a huge glass vase arrangement with about 10 phals in it, will be difficult :s
Btw Camille that phal i posted before with the keiki that hadn't flowered in 2 years? It has a tiny spike now and the keikis looking "ok" on its own, not growing though. And I saw ur new plants, Gongrats and hope things are getting better..

[camille1585]

Great news about the keiki spike! Sometimes you just need to be patient.

[opal]

I keep a variety of tropical plants and had experienced problems with gnats. They come to pots where there is decay and rot. 4 things resolved this problem for me:

1) yellow sticky traps - every fall I make sure there are some as that's the time adults find my place
2) carnivorous plants - nepenthes' just thrive with orchids and gnats
3) re-potting into clay pebbles
4) permethrin solution - it is sold under different names, I don't know how it is sold in USA and here you can find it in departments that deal with all stuff agriculture. I usually spray the windowsill and just remove dead bugs from it. I reapply every 2 months and have nothing flying around any of my plants anymore.

As for not being harmful, I have lost small grapefruit tree because larvae ate through the roots and I had to throw it away. I tried just repotting but didn't work in getting rid of gnats. CPs, traps and permethrin did the trick.

[Ray]

As others have said, fungus gnats are indeed harmful to the plants. When the larvae have finished eating the fungus that's growing on the potting medium, they will begin eating the roots.

Unfortunately, they are pretty good at going dormant when left dry, so just allowing the pot to dry out really doesn't eradicate them. A good dousing with an insecticide will kill them in place, and certainly repotting is a good idea.

[camillenad]

Thank you Opal and Ray, will douse in insecticide like you said, hope i get rid of them once and for all. Thanks again