Small flies around tomato base.

[tryagain]

This is my first year growing tomatoes and things have been going great but for the last few days there have been wht looks like small black flies buzzing around the bottom of the plants and into the grow bags.
Any ideas on what they are and how to get rid of them? The plants are in the greenhouse.
Advice greatly appreciated.

[Scarlet]

Fungus gnats? Is the soil very wet?
I've never had them on my toms...Try covering the soil over with newspapers.
I have heard sprinkling cinnamon (!) stops them but I've never tried it. Perhaps someone else will be along soon with some more info.

[WendyC]

Can also try little trays eg milk bottle lids of almond oil for them to drown in. At least they die happy.

[WilliamD]

That does sound like fungus gnats. If so, a thick layer of sand should help stop them getting back into the compost and likewise stop their larvae getting out of it. Like Scarlet says, they're encouraged by water/dampness but you won't want to hold back on watering your toms, so a barrier method may be best.

[tryagain]

That does sound like fungus gnats. If so, a thick layer of sand should help stop them getting back into the compost and likewise stop their larvae getting out of it. Like Scarlet says, they're encouraged by water/dampness but you won't want to hold back on watering your toms, so a barrier method may be best.

Would sharp sand be suitable to put around the tomato base as a barrier?

[Scarlet]

You could try covering the soil and sinking a bottle in, water through that so that the top of the soil isn't saturated.

[WilliamD]

Would sharp sand be suitable to put around the tomato base as a barrier?

Yes it should be fine. Nice and gritty, more so than beach sand, but still fine enough to make it tricky for the critters to get through.
In fact combine that with Scarlet's bottle feed idea and things should definitely improve.

[tryagain]

Ok guys will give it a try and see whats happens, thanks everyone.

[Two_Sheds]

small black flies

"Fungus gnats are often more numerous in composts that are constantly wet, allowing compost to dry can reduce infestations, provided this does not affect the health of plants." ... which is tricky, because tomatoes must be kept moist or they get blossom end rot

My toms are in Morrisons buckets with a saucer under it. I water into the saucer, not onto the compost, and I have no fungus gnats at all