[bedrockdave]

hi folks ,
this topic no doubt has been covered before but as I'm new to the site  perhaps you can help, Apart from blight my main problem last year was root fly even though I sprinkled derris dust around the base of the plants and used collars :? any suggestions

[Aunt Sally]

Bad luck Dave  

Were the collars a good fit around the stems  :?:

You could try encouraging beetles onto your plot - they eat the eggs and grubs.  

Small log piles are good harbourage for beetles.

[WG.]

Derris is non-selective and will kill predators too.

As Aunty says, fit collars snugly from 'Day 1'.  They do work.  I prefer large collars made from weed control fabric.

[Aunt Sally]

Derris is non-selective and will kill predators too.

And the beetles are your friend here Dave  

[gobs]

I found collars to be useless. If they are about, they just start laying on the foliage. Absolute waste of space. You want to encourage predators as per previous two advice.

[WG.]

I found collars to be useless.

:shock:

I use nothing else at all.

[gobs]

I found collars to be useless.

:shock:

I use nothing else at all.

Might be the same scenario if you did not use them.

I had an attack of them a few years back. So all that happened with the collars is that they lay the eggs on the plant, so I seriously think it's a con. It works if you do not have the problem in the first place, like companion planting with carrots and marigolds deter greenfly or whatever.

[Aunt Sally]

I found collars to be useless.

:shock:

I use nothing else at all.

Might be the same scenario if you did not use them.

I'd say you've probaly got loads of beetles about WG - you being ultra organic and all  

[gobs]

I found collars to be useless.

:shock:

I use nothing else at all.

Might be the same scenario if you did not use them.

I'd say you've probaly got loads of beetles about WG - you being ultra organic and all  

I should think so, Aunty.

[cawdor2001]

Could you put a very tight mesh over them to stop the flies getting in or would it have to be so tight no light would get in either?

cawdor

[cawdor2001]

Answered my own question, see below from Wondermesh

Wondermesh Insect Net is designed and tested to give the best quality insect net available for Cabbage Root Fly and Carrot Root Fly control. It is constructed from strong Polyethylene which has a life expectancy of 8 - 10 years.

Wondermesh is the most effective measure for the complete control of Cabbage Root Fly. As a physical barrier it offers 99% protection to the crop.
The net should be placed on the crop pre-emergence and secured in place with either soil or plastic pegs.

The net should not be removed until the CRF has become inactive in the autumn.  link below

Cawdor

http://www.wondermesh.co.uk/content/view/15/36/

[gobs]

Yes, all horticultural fleece will do. Should not forget that CRF will attack most brassicas, given the chance.

But not to despair, we lost them and nobody sprayed anything.

[Aidy]

Kind of agree with Gobs, this year I got hit big time and I always use collars made from carpet underlay, its thick and snug fitting but they still got through, Not sure what to do next year.  :?:

[cawdor2001]

Just build a big dome above the allotment and cover the whole thing with fleece, a minature version of the Eden project  

Cawdor

[gobs]

Aidy, I did a lot of things that year, would be hard to say which one helped how much, if at all, the bugs and birds might have done the most of it as far as I could know.

But I planted a lot of marigold all over the garden, lot of alliums and no brassicas for that summer except some radishes and ordered some over-wintering brassica plants, which were in clean compost in cold frames, covered with fleece and only planted out in the autumn.