[viettaclark]

Having followed discussion on this site and googling, I'm a carrot fly expert!
Although I have 18" raised beds I had quite a bad attack in my Early Nantes (planted in Feb.under cloche) which is not supposed to happen going by the life cycle!!!
Then I planted (as recommended) in early June in another bed, and blow me they've done it again!! The foliage on some of the Sugarsnax is turning orange and I had to whip out the other Early Nantes.
I've got Autumn King in the same bed which were planted late Jun and I've also got a patch in with my brassicas under scaffold netting. (They'll probably be the best of the lot!!)
Anyway...despite precautions it seems the fly can hatch out in one raised bed and get to another, hopping over the strawberry bed on the way, to lay the next lot of eggs! (Unless they're from elsewhere.)
I won't have any carrots for them to overwinter in so I'm hoping next year the beds will start off free of fly (I'll make doubly sure by digging deep and letting the chooks scratch about) and I shall erect a polythene barrier and see what good THAT does! Then I'll try the mesh...
What I need to know is WHERE DO THE FIRST LOT OF FLIES COME FROM?

[Christine]

I reckon that they thermal in a bit like very small gliders myself.

I want to know where the swift moths came from that attacked my carrots though. And why some of mine went straight to flower on skinny hard roots whilst others developed. Despite all being treated the same.

[viettaclark]

Been a funny old year. Caterpillars EVERWHERE and I've lost stuff despite watering....just shrivelled up!
And don't mention the mildew....aphids....flea beetle....
One good thing (let's be positive)...slugs and snails aren't a problem!
Just off to water again!

[DD.]

18" is not really high enough. 24" minimum is usually recommended and as Christine says, they can glide if the wind is behind them! A 24" polythene fence didn't do too badly for me,  but a total enclosure with enviromesh has been perfect.

With climate change, I reckon they are with us pretty well all spring/summer now.

I wouldn't rely on the fact that no carrots over winter = no fly in spring. They'll just bus in!

[Christine]

Snails are not a problem?   we've got ones the size of 50p pieces and bigger on our site - nothing small just enormous ones. So much for the winter slimming down the pests eh?

[JayG]

Snails are not a problem?   we've got ones the size of 50p pieces and bigger on our site - nothing small just enormous ones. So much for the winter slimming down the pests eh?

It's all relative, Christine (and boy, don't snails have a lot of relatives!) 

[RichardA]

I have to say I am pretty lucky that nothing much has ever eluded me in terms of good results in veg gardening EXCEPT CARROTS when I fail time after time, too close, too many attacks, too late, too early etc. BUT BUT BUT this year has been excellent - what did I do different -- 24inch screens all round using fleece as I had it, screens not too wide apart so each bed quite small and being more patient and more exact with everything. I have turned a corner, yippee. Comment from her indoors -- this carrots are superb -- why did you not sow several more rows  -- can't win
R

[viettaclark]

How big are the flies? (She who is an expert doesn't know!!)
Just wondering how you rig up your fleece barrier and whether I could use something cheaper like debris netting? (Got loads of it)

[RichardA]

very small, I believe debris netting not to be suitable -- others may know better. I use roofing battens about 50 mm square knocked into ground and staple gun enviromesh or fleece to it. Not perhaps best way as rips when taken off but can lift whole thing and set out again. Sure others will have better ideas
R

[JayG]

Can't add to what DD has already suggested; growing at least 24" off the ground or using a 24" high barrier around the crop works pretty well, but not if the barrier has a mesh size large enough to let the carrot flies through (they are about the size of houseflies.)

Environmesh is the best solution if you want to grow your carrots at "ground" level, otherwise you will be trusting to luck! 

[gillie]

"What I need to know is WHERE DO THE FIRST LOT OF FLIES COME FROM?"

They lurk around in hedgerows living off carrotty weeds which are their natural food until someone sows a row of carrots and they smell a feast coming up.

Gillie

Edited to include the username of the original poster.

[Totty]

Do the fly have the ability to burrow or do they get into the carrot just below the surface?

Seems a silly question but does earthing up the carrots a little bit have any effect?

[DD.]

You can find them all the way down the carrot.

[Togalosh]

What I need to know is WHERE DO THE FIRST LOT OF FLIES COME FROM?

God...as with everything else of course.

I'll be having a word with him the next time I'm in a church.. I hope no other plot holder is there at the same time as I've a very long list to go through with Him.