Can a solitary fruit fly really ruin 5 gallons?

[BruinTuns]

Hi lads
last summer, before I was even thinking about home brewing, I noticed an unusually high number of fruit flies around my fruit bowl.
I've no particular problem with insects and wasn't overly bothered, but now I've just started home brewing and all the reading I've done suggests that just one of these persistent little b@stards can ruin a batch of beer.
Reading more, I cling-filmed a bowl which contained a couple slices of banana and poked a few holes in the clingfilm with a toothpick.
It worked, I caught about a dozen (even at this time of year) over a few days and haven't now seen one for 48 hours.

"Yes, questions"... as Rutger Hauer says in Blade Runner:

Can one fly really destroy an entire batch?
Does anyone else do the pre-brew trap routine?
Could it be that the banana was bringing the flies in, and that if I hadn't bothered trying to eradicate them that way they wouldn't have been there at all?
Is an airlock the only sure way to keep them out?
Can/will they get past a non-airtight fv lid?

As always any advice much appreciated.

 

[MyQul]

I, like you , just make up a little trap and that generally deals with the little buggers. Its easier for them to get into the trap bait than to an FV so they go for that then all get killed

I get a jamjar put a litter cider vinegar in it and a drop of washing up liquid (to break service tension) , don't cover. Seems to trap em a treat

 

[BruinTuns]

I tried white wine vinegar as well, same method as for the banana. the two jars were side by side, and not a single fly went for the vinegar.
Maybe cider vinegar would have worked better, but I didn't think they were so discerning.
Didn't know about the washing up liquid, I'll try that next time, thanks for the tip.

 

[JAK]

Hi lads
last summer, before I was even thinking about home brewing, I noticed an unusually high number of fruit flies around my fruit bowl.
I've no particular problem with insects and wasn't overly bothered, but now I've just started home brewing and all the reading I've done suggests that just one of these persistent little b@stards can ruin a batch of beer.
Reading more, I cling-filmed a bowl which contained a couple slices of banana and poked a few holes in the clingfilm with a toothpick.
It worked, I caught about a dozen (even at this time of year) over a few days and haven't now seen one for 48 hours.

"Yes, questions"... as Rutger Hauer says in Blade Runner:

Can one fly really destroy an entire batch?
Does anyone else do the pre-brew trap routine?
Could it be that the banana was bringing the flies in, and that if I hadn't bothered trying to eradicate them that way they wouldn't have been there at all?
Is an airlock the only sure way to keep them out?
Can/will they get past a non-airtight fv lid?

As always any advice much appreciated.

Can one fly really destroy an entire batch? It could, it would depend what the fly is carrying. The microorganism that the fly deposits in your beer would have to out compete billions of yeast cells for the sugars in your beer. Given that a fly is not the cleanest of creatures I'd assume it'd be carrying some not very nice microorganisms.
Does anyone else do the pre-brew trap routine? I don't really remember having this problem to be honest, everything up to the point of the boil isn't a problem as that should sterilise most things.
Could it be that the banana was bringing the flies in, and that if I hadn't bothered trying to eradicate them that way they wouldn't have been there at all? Fruit flies tend to be attracted to fruit. However it could be any number of other things.
Is an airlock the only sure way to keep them out? Can of deodorant and a lighter? Venus fly trap? As many spiders as you can welcome into your home as possible? - Your traps probably the best technique.. or those sticky green sheets you can hand up.
Can/will they get past a non-airtight fv lid? Not likely whilst its fermenting due to the CO2 being vented. Up until fermentation has taken hold I'd think it's where the fly would want to get too.

 

[BruinTuns]

Thank you again JAK for the input, and the laujh!
"Can of deodorant and a lighter? Venus fly trap? As many spiders as you can welcome into your home as possible?"
;-)

 

[MyQul]

Could it be that the banana was bringing the flies in, and that if I hadn't bothered trying to eradicate them that way they wouldn't have been there at all?
.

Fruit flies love wort. Remember it's basically just sugar water and it the sugar in fruit that attracts them

 

[brewpirate]

Just dont age it and you will be fine

 

[BruinTuns]

Thanks lads.