Greenhouse beasties

[Newbie]

Hello,

Yesterday i went into my GH to open it & let it have a good air out whilst the weather was reasonable, whilst in there i noticed that several of the pots (2 comfrey & 4 Dahlia, all yet to sprout) were crawling with little black flies. I promtly put the pots outside & the floor underneath the pots were also crawling with the little beasties.

My GH is unheated & sited on a patio therefore no soil beds in there, it is insulated with bubblewrap & there has been not much in there over winter except some wrapped up fuschias.

Is this infestation the result of bad GH hygiene? And how do i get rid of them? I was planning on just leaving the bubblewrap in place over summer to act as a kind of sunshade - is this a bad idea?

Sorry for multiple questions!

[Sanjo]

Lack of ventilation can be a factor. I too have my GH bubblewrapped, and have done for many years. I have only just replaced it and I buy it new. The last lot managed 5 years before it started to disintegrate. One thing I would say about leaving it in situ is that you will shorten the life of it. If it's made up of replaceable odds and sods (ie fruit packaging from the supermarket then not a problem) but if you have paid out for it then it's more economical to protect it. I remove mine mid April (may be a bit later this year though!) and roll it carefully and store it in a black sack in the shed or somewhere shady. Leaving it up will make the GH extremely hot.

[Newbie]

Hmm, perhaps i am better removing the bubblewrap & giving the whole greenhouse & good clean out whilst i'm at it. I've had the GH 2.5 years and the insulation has been on it for 2!

[Two_Sheds]

Do you think the flies are fungus gnats?
Most likely cause would be over-watering, and watering the soil surface instead of into the saucers under the pots

[Brengirl]

That's what I have and been and gone and done. I have read that if I water the soil with an insecticide this will kill off the eggs and larvae. What do you think?

[Newbie]

Have just googled Fungus Gnats & they look like the little beasties!