[Sue32]

I sowed carrots and marigolds ( and some other salads) and covered them all with enviromesh.  Determined to keep them pest free.  Everything is growing really well but when I pulled it off this am I found everything covered in whitefly - they seem to think its a great green house.  Where did they come from though as I thought e-mesh kept everything out!
What do I do now?  resort to sprays?

[Sue32]

please help - what have I done wrong with this mesh .....
will the whitefly pests hurt the crops and what can I do about them now?

[Paul Plots]

An interesting dilema!

I guess the whitefly (?) love it - safe from preditors and disturbing draughts... I think I would consider removing the mesh and letting the fresh air and other bugs in..... sounds as if you are housing a pest to me anyway.

I imagine they either arrived by creeping under and then multiplied rapidly or they were in the soil/on the emerging crop when you covered it.

There's probably a predator sold in pupa / larval state that would hunt out and eat the whitefly but it could be costly - this would enable you to keep the mesh in place and use a predator species as a control in a confined space.

I am sure someone else will have better advice. 

[Sue32]

thanks learner, I'll investigate the predator route today, and if no luck take the covers off over night - hope the carrot root flies don't find us. 
Are the whitefly actually a problem to the crops - look horrid.
This is my first season as a veg grower and keep reading about the carrot root fly so was trying to take all precautions not to lose my first crops - seems I've created some  other problems instead - still I'm learning.

[Salmo]

Whitefly are tiny and may well get through normal enviromesh. They do sell a micromesh version.

The whitefly should not harm the carrots.

If you leave the cover off overnight you risk carrot fly. If they fly in, attracted by the smell of disturbed carrots they will have time to lay their eggs. When you replace the covers they may well be trapped in there. Carrot fly heaven!

[Sue32]

Thanks Salmo, scrap plan A then.  Seems it's the wrong sort of mesh (like wrong sort of snow etc).  I do have 2 types bought in different stores and can see the difference.  The holes are very small in one (over the carrots) and  very very small in the other (over the cabbages which are completely pest free).  Hope it will still do teh job in keeping the Carrot flies out though.
Fortunately (look for the good bits) the whitefly haven't gone for the salad stuff yet...

[Paul Plots]

Lots of talk these days about using barrier mesh to protect from carrot fly - but carrots have been grown for a very long time without it...

Whitefly will feed on carrot foliage - do no great harm but can / may introduce disease and weaken the carrots if they are trapped there in the cosy warm free from the breeze and anything that might stumble along and eat them.

Personally I cope with a bit of carrot fly damage (and no protection) - over the last few years it has been no more than superficial surface nibbling. Using a veg peeler as you'd normally do removes most damage prior to cooking...perhaps I am just luck?

So don't overly panic - all is not lost... 

But... Salmo is very correct about not trapping carrot fly under the mesh - that could cause problems big time.