Bad compost! (B&Q)

yumyums

Hi all
Was wondering if I could pick your expert brains on this subject

I bought some seed & cutting compost from B&Q recently when I ran out of the wilkos multi purpose compost I was using for sowing my seeds.
As soon as I started using the B&Q stuff I noticed a lot of little black flies around the compost (sort of look like fruit flies? Never really examined a fruit fly that closely so I can't remember what they look like!)
Anyway, the flies seem to stay on the surface of the compost in the pots and now there are loads of little white grubs (I guess the flies' larvae) crawling around in the compost. I was trying to ignore it until today I notice one of my alpine strawberry seedlings has completely disappeared. I don't know if it has been eaten.

Is it possible that the compost I bought was contaminated? All the seedlings I did in the Wilkinson's compost seem to be free of flies.

What can I do to get rid of these flies & the grubs in order to save the rest of my seedlings. Had a look at some pesticides today and they are all for blackfly, greenfly, spider mites etc and these are not what I've got.

Thanks for any help!

emiff6

What you have is sciarid fly or fungus gnat
http://www.just-green.com/Article/181/Scarid-Flies-or-Fungus-Gnats.html

The larvae feed on plant material in the compost, which of course includes roots of the plant in the pot. Those sticky yellow white-fly traps work on the adults, but to remove the grubs you need something that can be watered into the compost - provado organic bug free might work, it works on springtails.

Kevstir

bug clear ultra for pots worked for me , had them really bad on my house plants, used the bug clear and been fly free for months

yumyums

Thank you both. I'll look into both of these options.
Only thing is, I looked at some pictures of the scarid flies and the flies look the same I think, but the larvae definitely look different - they don't have any black bits on them.

emiff6

They are so small it's hard to see their tiny black heads against the compost.

yumyums

Just a little update in case anyone has similar problems.
They definitely were sciarid fly... I started seeing some of the larvae with black heads in the end. What was confusing me before is there were some other white grubs with tiny antennae like things that weren't the sciarid fly larvae - still not sure what they were...

Anyway, I bought the organic bug clear but didn't have any success with it. I tried spraying on the surface of the compost and avoiding the strawberry seedlings but didn't manage to miss them completely and burned the leaves of the seedlings. Also, the spray didn't seem to have any effect on the squiggly larvae. I'm sure it'll come in handy throughout the rest of the year for use on other pests!

I didn't try the vine weevil killer as it is very expensive but I did read somewhere that it works on the larvae.

In hindsight I wish I had just gotten rid of the affected seedlings in the first place as they have now spread to one of my chilli seedlings. The larvae seem to have eaten / damaged the roots of some of the seedlings as I noticed them falling over and when I pulled them out they didn't have roots anymore. Interestingly, they don't seem to be affecting any of the pots in which I've covered the surface of the compost with vermiculite (at least I haven't spotted the little b*ggers yet!).

Thanks again for the replies.

Kevstir

i didn't use the spray m8 it was the bug clear ultra for pots, its little sticks you pop in the pots, 100% worked for me, my back room was the worst, was teeming with the little !!!!!!s (got over wintered fuchias on my window sill) and been fly free since i put the sticks in, think it took about 2 weeks to get rid of them, that included hoovering them up when ever i seen them lol

http://cgi.ebay.co.uk/SCOTTS-BUG-CLEAR-ULTRA-POTS-20-X-INSECTICIDE-SPIKES-/130488033409?pt=UK_Home_Garden_Garden_Plants_Weed_Pest_Control_CV&hash=item1e61b16081#ht_500wt_1156

mind you if your using them for fruit & veg seedlings they might not be suitable

yumyums

Kevstir wrote: »

i didn't use the spray m8 it was the bug clear ultra for pots, its little sticks you pop in the pots, 100% worked for me, my back room was the worst, was teeming with the little !!!!!!s (got over wintered fuchias on my window sill) and been fly free since i put the sticks in, think it took about 2 weeks to get rid of them, that included hoovering them up when ever i seen them lol

http://cgi.ebay.co.uk/SCOTTS-BUG-CLEAR-ULTRA-POTS-20-X-INSECTICIDE-SPIKES-/130488033409?pt=UK_Home_Garden_Garden_Plants_Weed_Pest_Control_CV&hash=item1e61b16081#ht_500wt_1156

mind you if your using them for fruit & veg seedlings they might not be suitable

I don't know why I thought you recommended something else and looked at the wrong thing.
Those sticks look good - probably not suitable for tiny seedling modules but I'll bear them in mind in case they have transferred to the houseplants
Thanks

roddydogs

are you saying the flies lived in the compost in a sealed bag?

yumyums

roddydogs wrote: »

are you saying the flies lived in the compost in a sealed bag?

I'm not certain but all I know is there weren't any flies around until I opened the bag. Also found a woodlouse (or something like it) when I was scooping compost out of the bag.
I didn't think about it much at the time as I'm really new to gardening and haven't handled much compost but thinking about it now, it's supposed to be sterile, right?

Lotus-eater

roddydogs wrote: »

are you saying the flies lived in the compost in a sealed bag?

I had fungus gnats last year from fresh compost, took me ages to get rid of them, they spread to everything.
I think in the end, I just took all the pots into the greenhouse for a few weeks (it was the summer) and they went away, or got eaten or something.