fruit fly infestation

[Courtney Edwards]

I have a mad infestation of fruit flies in my greenhouse. I should say "very small flies that look like they might be fruit flies" since I haven't busted out the microscope to correctly identify them. I understand that I can trap them (bottles with vinegar, sticky traps, etc) but I would like to figure out a way to prevent them from even happening. There isn't any fruit, or rotting tomatoes or really much at all left in my greenhouse since it's winter in Canada, just some winter greens in my aquaponics system. They seem to congregate around my gravel grow bed, does anyone know why? Can they hatch in the water of my deep water trough?

I recently pulled out most of my summer plants so there is a fair bit of old root matter that is near the surface of the gravel, is that enough fodder to create these little monsters? I would have thought it was too cold for them to hatch but every time we get a few days of good weather their population explodes again. I've been successful catching them with vinegar and dishsoap, but does anyone have any ideas for a long term solution on how to get rid of them?

 

 

[TCLynx]

I expect they are probably fungus gnats, look very similar to fruit flies.  Not sure how best to get rid of them form an aquaponics system though.

[Courtney Edwards]

Thanks for the reply, it gave me somewhere to start looking.

 

Courtesy of the UBC Botanical Gardens forum is this description of the culprits, in case anyone else wants to do some reading: http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn7448.html

 

At UBC they use a predatory plant called a Sundew (which is awesome!), but sadly it goes dormant in winter.

The UCDavis page recomends adding predators like rove beetles (family Staphylinidae) and ground beetles (family Carabidae). A little further reading suggests that a few of those black ground beetles in my grow bed might balance out the fight. Ironically, I just evicted one from my gravel the other day, maybe he's still around and will accept an apology.

 

And finally, some pictures of the beetle arsenal available to me here in BC:

http://www.pbase.com/terrythormin/bc_carabidae

 

 

[TCLynx]

Very cool that they have so many beneficial bugs to recommend.

[Jon Parr]

Two thumbs up for sundews. Somewhere in another post I was introduced to them, and they will forever more be a part of my aquaponics growbeds. I found them for sale at orchard supply, for $6 each. The instructions say to keep them saturated with distilled water, so I bought two of them. One I placed in a Dixie cup and keep it topped off with distilled water, and the other I dropped the plastic flowerpot low enough in the gravel so that each flood cycle reaches the bottom of the container allowing it to soak up AP water. Both are doing fine, and one just shot a flower spike. Can't wait to see the blossoms. White fly and fungus gnat populations are on the decline. 

[Roger]

There's plenty of methods used to remove fungus gnats in hydroponics systems.  However, I believe some of the methods might be toxic to fish.  Here's what I would suggest.  Fungus gnats love moisture.  Moisture dictates where they will lay their eggs.  I would definitely recommend sticky yellow traps.  These will catch the adults and prevent them from laying new eggs.  Also, if you're not using siphons and instead using timers to fill your GBs you could shorten your fill times to your GB.  This means that the media on the top would most likely stay drier which would discourage fungus gnats from laying eggs. 

[Keith Rowan]

predatory nematodes, fish safe

http://greenmethods.com/site/biocontrols/nematodes/