Flies on a houseplant, help please

[kippersmum]

We have a huge fern in the bathroom, it has lots of black flies on it. Having googled I think it they are www.bbc.co.uk/gardening/advice/pests_and_diseases/identifier.shtml?black_fungus_gnats

I garden organically outside but can't cope with the thought of flies in my bathroom so I'm happy to zap them with a pesticide if needed. I'm not sure about using pesticides on houseplants in bathrooms though... is it safe?

I can't get rid of the fern as DH is very attached to it having brought it back to life after getting it half dead, very cheap, from B&Q.

Anyone got any ideas as to what to do? TIA

Those flies are fairly easy to get rid of. You don't need to get heavy duty pesticides, the soap based ones would do the trick. Apply it on the leafs and the earth. Take the plant ouside to do it. You need to treat the plant weekly for a while and you should be fine.
The only time I witnessed those bugs being a real problem, the plant was huge and v v heavily infested. We had to clean the roots bare, spray the insecticide soap on the roots and give fresh soil to clear the plant, but this was an extreme case.

p.s. they tend to develop when a plant is overwatered.

If you're in the south stick it outside somewhere sheltered/ makeshift greenhouse over maybe.

My first kill all pests attempt is use old soapy dishwater in a spray bottle and spray soak the plant, i second remove the soil and replace with fresh. Wash any outer pot and plastic liner thoroughly in hot soapy water.

Respray every couple of days for a week or two.

I try to move sick plants out the house because i don't want them to pass on anyting to my other plants.