First off I am new to the forum so play nicely please.

I have searched the forum and all over the internet but can't seem to find an answer.

Since are central heating came on we have been infested with extremely small black flies. I had noticed them coming out of a cactus plants soil, and as much as I didn't want to was forced to move the plant outside. Now we have flies coming out of other plant pots inside the house.

My question is what are they exactly and what can I do to get rid of them. Hopefully without losing my plants.

To the forum admins, I am sorry if this is posted in the wrong section as I couldn't find an indoor plant section to the forum.

Any help with my problem will be greatly appreciated thank you.

On Jan 10, 9:34*pm, darronb
wrote:
First off I am new to the forum so play nicely please.

I have searched the forum and all over the internet but can't seem to
find an answer.

Since are central heating came on we have been infested with extremely
small black flies. I had noticed them coming out of a cactus plants
soil, and as much as I didn't want to was forced to move the plant
outside. Now we have flies coming out of other plant pots inside the
house.

My question is what are they exactly and what can I do to get rid of
them. Hopefully without losing my plants.

To the forum admins, I am sorry if this is posted in the wrong section
as I couldn't find an indoor plant section to the forum.

Any help with my problem will be greatly appreciated thank you.

--
darronb

What you have is Scarid fly
http://en.wikipedia.org/wiki/Sciaridae

On 10/01/2012 21:34, darronb wrote:

Since are central heating came on we have been infested with extremely
small black flies. I had noticed them coming out of a cactus plants
soil, and as much as I didn't want to was forced to move the plant
outside. Now we have flies coming out of other plant pots inside the
house.

My question is what are they exactly and what can I do to get rid of
them. Hopefully without losing my plants.

As the other replies have stated, these are sciarid flies. Don't bother
with pesticides - in my experience sciarid flies are resistant to them.
The yellow sticky sheets are effective, but will not deal with all the
flies. And if one gets through to lay eggs, you will have dozens more
to deal with.

They need damp compost to survive, so dry soil will eventually see them
die out. In any case, unless your cacti are of the christmas cactus
type, they shouldn't be watered at this time of year. They should be
left in a cool, well-lit window and kept completely dry until April. It
is best to not close the curtains with the cacti on the glass side, as
although many are frost-resistant if completely dry, some aren't, and a
severe frost might see the temperature fall enough to damage them.

--

Jeff

As others have said, sciarid flies. Keep the top of the compost bone dry to deter them.

But since you have cacti, what you need to do is decant the cactus plant and check the roots for small white grubs - the larvae of the fly are capable of munching through all the roots of anything which has soft fleshy roots - hippeastrums and other bulbs, cacti etc. Then repot the cactus in new, rather gritty compost, and cover the top with a layer of grit.

It's also worth killing any flies you see, before they can go and lay more eggs. You often find them crawling over the outside of the pots. And domestic fly killer works on the flies, although not on the grubs.

By the way, no need to apologise to forum admins - all this forum does is repost your post to one of the gardening newsgroups, in this case uk.rec.gardening. It's the folks on uk.rec.gardening who are answering your question, nowt to do with gardenbanter.