I just checked one of my fermenters and there appeared to be fruit flies in my air lock!!! They were not there last night…Is this beer trashed?! I just replaced, cleaned and sanitized the air lock…I hope it is not ruined…
if they did not make it through to the wort you are fine. that is what the air loc is for. clean and sanitize again and replace.
Awesome! I don’t think they made it through!
They can’t fly in through the airlock. But you need to find the source and get rid of them - bananas are a common problem (be sure to wash them off when you bring into the house) and you can make a trap by putting apple cider vinegar in a shallow dish and then adding a drop or two of liquid dish soap (the vinegar attracts them and the dish soap breaks the surface tension so when they land on the vinegar they just sink).
+1 I would be using vodka in my airlock as well.
I had them right in my beer once. scooped them out and drank it anyways. seemed alright to me but I did drink it quickly, before it went bad.
I have had a fruit fly issue the last couple years now. Not sure where they come from but they keep on laying eggs in the hose that goes from my drip tray to the milk jug attached at the end of the hose. I have a fruit fly trap in place but the only way I can fully get rid of them is to take the drip tray off toss out the hose and milk just and then soak the tray in PBW for a couple days until they all die off. It a major pain in butt.
maybe if you put a barrier between the driptray and the drain hose like a thin sponge that you could rinse with sanitizer once in a while.
I’ve had trouble with fruit flies in my apartment for the last few years. My solution is to take a bit of something like cloth or a paper towel, make a “chef hat” out of it so it goes over the top of the air lock and has some air room under for breathing, and scotch tape that snugly in place so the flies can’t crawl under the sides.
I put the scotch tape on the outside of the paper towel and just make it snug, without taping directly to the air lock itself. Once I’m done with the air lock, then I can pull the top and the paper towel off all at once, and it slides away. No tape residue.
I’ve been having a problem with those little bastards as well, but this little trap works very well. I use apple cider vinegar and it attracts them and they eventually die because once they fly in, they’re not able to figure out how to escape. 
+1 to what bluesman said. You can even use a clear beer bottle with a tighter paper cone and the damn fruit/drain flies will never escape!
This year was especially bad. At least here in Maryland. One day I was outside walking down the street and I hit a wave/school/whatever of them so thick and big (I’m talking thick as shite and a block long) that when I got home, my whole shirt and face and hair was covered in the damn things… I was inhaling them and it was pretty gross.
Anyhow, when they got especially bad I realize they were coming from some of my empty beer bottles. Even though I’d rinsed them 2 to 3 times after pouring, they loved being in them and lord knows what the damn things were doing in there.
