Sciara flies /Fungus gnats

[robinast]

A small fungus gnat population have been always present in my greenhouse. Usually, they do not cause much trouble - unless they lay into young seedlings pots. Occasiaonally I've experienced very painful losts due to them...
It is possible to get rid of them by using some insecticide - but if to be honest, I'm not just very eager to use them (though I do use, if absolutely necessary). Luckily, I accidentally found a good way to get rid of them without use of any insecticides.
Generally, I keep my sowings at +30...+35 C daytime and around +25 nightly. Nevertheless, it happened so that in one of my seedling boxes, the temperature raised well above +40 and remained so during several nights. And to my greatest surprise, after that I saw several dead Sciara worms between the seedlings on the ground while seedlings themselves do not seem to have any damages.
Just recently I had noticed some Sciaras flying around and I had started to worry about what damage they could cause. Now it seems that I have no reason to worry any more! Of course, I still will keep my eye on the seedling boxes as previously. Nevertheless, I think I can say to myself "No worries, mate!" now.

[fanecchissimo]

you are right. sciara flies disappeared after my greenhouse went above 50°C.  they are more sensible than cacti to heat!

[fanecchissimo]

if i can add, you should catch some spiders outside and place them inside the greenhouse. wonderful work for free

[Simon]

I top dress all my pots with a layer of gravel, no more fungus gnats, and also less soil splash so less problems with fungal disease too.

[andrea.a]

Interesting topic!
To prevent sciara attack i use to put a small fan near the seedlings (pc cooling fan), it prevents adult sciara flies to "land" on the pots and deposit eggs (or larvae, i don't know), it also helps with fungal infections.
Andrea.

[fanecchissimo]

fans are great all year long apart from frozen days, they cool off more the plant!

[danskibsted]

I have had problems with sciara flies also. When I place my newly made pereskiopsis grafts inside the humid boxes, I see many sciara flies after 1 week. They eat the grafted seedlings
Any good tips on how to get rid of this problem? I can not raise the temperature, and a fan is not possible inside the boxes. Maybe there is a good insecticide?
Any help is apreciated!
Dan

[robinast]

Dan, did you say that the fungus gnats eat the grafted seedlings on top of the Pereskiopsis stock?! 
Their larvae live in soil and feed on the young seedlings (among other organic matter) and the adults do not feed at all...
http://www.ext.colostate.edu/pubs/insect/05584.html
Sometimes I have used Vertimec, and insecticide and acaricide, mainly to control spider mites - but it should be effective against sciarids as well
http://www.syngenta.com/global/corporate/en/products-and-innovation/product-brands/crop-protection/insecticides/pages/vertimec.aspx

[Farel]

This is my 1 post so hi everyone! Greetings from Poland!

To cope with sciara flies is use very eco friendly method - Drosera plant. It catches all adult specimens.

[robinast]

Drosera? Fine! Sounds like a pefect solution! 

[Onzuka]

Here in the UK you can buy a big aerosol can of household fly killer for £0.99 and it kills the adult sciaras in minutes!  Sprayed into the atmosphere, as it is supposed to be used, it has no effect on the cacti.

Steve

[Simon]

I love the Sundew idea! Welcome Farel!
I have used sticky traps in the past but it looks like the sundew does a better job so I reckon I might try some in the propagator next winter, they grow wild by the thousands in the bushlands around where I live!

[danskibsted]

Dan, did you say that the fungus gnats eat the grafted seedlings on top of the Pereskiopsis stock?! 

It seems like it. The boxes with sciara flies has alot of dead seedlings (30-50%!), and the boxes with no sciara flies has only very few dead seedlings (0-5%).
I guess there must be some sort of relation.

[robinast]

Hmmm... the explanation could be that they carry fungus spores or hyphae onto the cut surface and then the tender grafts just rot. Of course, I dont' know - but as the adults don't feed, this seems quite logical explanation. I myself have never had such a problem with grafts. Yes, sometimes larvae have damaged young seedlings - and that's all.

[Simon]

Could it be something else that is hard to see like thrips or mites?
A photo of native sundews and terrestrial orchids near our home...
<a href="http://www.flickr.com/photos/36369542@N04/10061394504/" title="Sundews and terrestrial orchids. by The Living Rock, on Flickr"