[Growster...]

This is the second year we've used the stuff, well tucked in at the edges, and totally covering the carrots. It's stretched out on a set of wire hoops, and the carrot leaves are nudging up under it, but the carrots have no sign of fly - yet...

I promise that I will report back if there are any affected, but it worked last year, and so, fingers crossed!

[GrannieAnnie]

It worked for me too last year Growster!

[JayG]

If you Gurgle "carrot fly size" you will discover that the adult female is anything from the size of a small house-fly, a small fly, or 5mm (up to and probably beyond 8mm) - I sometimes wonder if anyone has actually seen one, never mind measure one (I haven't either, but I have lost all my carrots to the wee/not so wee little swines in the past!)

I guess that leaves it up to us to do the calculations as to mesh size  , but apart from the risk you take from lifting it to weed or whatever, it's worth remembering that they may be rubbish fliers but only government ministers caught fiddling their expenses can crawl better than they do, so don't leave any little gaps round the edges. 

[plum crumble]

me too Growster! have had a fine crop - first year ever without the dreaded fly - my debris netting and hoops worked a treat.

[GrannieAnnie]

Mine were pegged down JayG!   

[Growster...]

Perfect comparison, Jay, I have to admit too, that I keep turning round to see if they're about to gang up on me before I lift the net!

Glad it worked for you, too folks, the mesh is really very fine, and hard-wearing, so it copes with all sorts of knocks as well!

[compostqueen]

I think carrots grown in old compost - either home made or turned out used growbags-  is good for carrots rather than growing them in the allotment soil which is probably playing host to carrot fly larvae

I mix my carrot seed with spring onion seed and sow the two together. Cover with fleece or Enviromesh and harvest 

[Growster...]

I don't know if the larvae over-winter, CQ, but I try and rotate as much as I can!

[JayG]

The larvae do overwinter in the soil Growster, not just after carrots but parsnips, parsley celeriac and celery if your luck really has run out!   

Worth bearing in mind when it comes to rotation, as the thought of actually trapping them inside your purpose-built 5-star sheltered accommodation is not a happy one!