Fact, fiction or old wives tale

[Bill HH]

People say I surrounded them with environmesh or I grew them on my roof etc and had no damage.

I grew good carrots for years in all sorts of conditions and had no carrot fly damage. But no damage doesn't mean the methods are stopping the flies, it just means the flies are not there.

Last year I got a lot of damage so this year I am covering them all with mesh. Its the only way.

As for the fly itself, the clue is in the name FLY, I find it unlikely that cant reach more than a few feet and even if they couldn't they have legs don't they? my garden is walled in with a 7ft stone wall apart from two gates maybe I should just mesh the gates? I don't think so.

[Penellype]

I get a little bit of damage to unprotected turnips in the ground. Is that the same carrot fly, when they can't find anything tastier?

If they are white maggots they are cabbage root fly. Different species of fly, same type of damage

[bootsnbraces]

It took me a long time to prove this to other allotment holders - what do flies do when they land on walls? they walk up them! as do carrot flies and a hard to get bit of camera phone footage showed them doing just this.. walking up the fleece barrier over the top and down the other side

waste of time

[Bill HH]

I have carrot root fly damage in my poly tunnel. A container that is 4feet off the ground. There are no thermal ait currents that I can detect inside. My conclusion is that the blighters flew there.

[Nicos]

You could have wafted them in with you when you walked into the PT Bill

[Penellype]

I think there is some confusion going on here. Nobody is saying that carrot flies can't fly. However, the theory that barriers can keep them out is based on their apparent tendency to fly low to the ground when they are looking for somewhere to lay their eggs. This makes reasonable sense - carrot flies are insects which only lay their eggs on a particular family of plants, which mmostly grow fairly low. You won't find carrots 10 feet up in the air under natural conditions.

What I suspect happens is that a carrot fly wanting to lay its eggs smells a carrot (which apparently they can do at a distance of upto a mile) and flies along close to the ground looking for it. If it meets a solid object it may fly up and over it or it may not - some people's experience implies not.

There is a possibility that there are different types of carrot fly in different areas. Maybe the carrot flies in some areas have some mutation which "programs" them to fly higher. In areas where carrots were mostly grown in enclosed spaces these flies would be the ones that found the carrots and reproduced, so once this appeared it would rapidly spread. In areas where carrots were grown in open fields there would be less advantage in this sort of thing and it might not spread through the population. I have no evidence for this, but it is a possibility.

[teakdesk]

I have carrot root fly damage in my poly tunnel. A container that is 4feet off the ground. There are no thermal ait currents that I can detect inside. My conclusion is that the blighters flew there.

You have no air vents in your tunnel? Sounds a rather stiffly, airless place!

[Bill HH]

You have no air vents in your tunnel? Sounds a rather stiffly, airless place!

Yes I have air vents, the point is it was suggested that if the flies cant fly higher than a few feet then it must be the wind / air currents that lift them up. Which is why you don't get so much damage in a poly tunnel. I am merely pointing out that I have damage in the tunnel in a container 4ft high and if they cant fly that high and there are no thermals how did they do it? So what I deduce is that they can and do fly higher if they want to and that the only real protection is netting all over and not just a low fence..

[BUFFS]

I have mine in 24ins high raised beds and no sign of any damage but when I sowed them at ground level they got chewed to bits..

[Noosner]

I'm convinced that once insects find a crop they like, they spread the word among themselves! I cannot believe the numbers of cabbage white butterflies that are sniffing (or whatever it is they do) around my 5 PSB plants. A fortnight ago, there were only two - today I counted 12.

[Nicos]

Probably pheromones?

[Martin H]

Once plants start getting eaten by caterpillars they get quite niffy. I wonder if the pregnant mum butterflies are attracted by the smell?

[Noosner]

Crikey, I didn't think of either of those things, Nicos and Martin. I guess that once the leaf is broached, it will attract more insects. A bit like blood attracting sharks!

[Farmer_Gyles]

I've been growing carrots in window box tubs for years .... always used a cheap multi-purpose compost .... my veggie patch is a few inches of soil on top of chalk hill, quite stoney, not good for carrots .... they grow very slowly in the multi-purpose compost, but they do grow and always a good shape .... i should probably have used a better compost or fed them, but never have ...

from now on i'll be growing them on the new allotment .... much better ground for them .... i'll be sowing some this weekend ....

think i've been lucky as i've never had carrot fly .... apparently it's always a problem on the allotments .... i'll cover each row using a DIY 'cloche' tunnel made from old wire coat hangers and net curtains .... fingers crossed!

[Penellype]

Don't give carrots too much feed - they will just produce a lot of greenery and forked roots. They do best on poor, sandy soil.