Topic: Unidentified caterpillar eating my cabbage seedlings

[George the Pigman]

I have some savoy & red cabbage seedlings growing in my greenhouse and nearly ready to go out to harden off. Today I noticed holes nibbled in them and found tiny yellowish caterpillars about 2-3mm long on them . They look too small to be the large or small cabbage whites. Ant entomologists among recognise them?

[picman]

George . are these they , see my post
http://www.allotments4all.co.uk/smf/index.php/topic,80332.0.html

[johhnyco15]

yes diamond back agreed

[Deb P]

Saw some of these little beggars on top of my debris netting over my Brassicas today......they seem too big to get through but I'm not lifting it to find out!

[George the Pigman]

Yes that looks like it. What insecticide, organic or not organic, is recommended?

[johhnyco15]

Yes that looks like it. What insecticide, organic or not organic, is recommended?

I've still got Pickett and use it on nastys  however any pesticide that says kills caterpillars will work the bayer one is good but having a senior moment on the name hope this helps

[squeezyjohn]

Because diamondbacks have been a major pest in southern Europe for years - they have been sprayed for years and apparently they have developed a remarkable immunity to most pesticides.  You can try, but don't be surprised if it doesn't work.

[picman]

Fed the little critters on Pyrethium , seemed to work , I may have saved a few plants, time will tell...

[Paulh]

Finger and thumb work well ...

[George the Pigman]

Johhnyco15 I think you mean Provado Ultimate Bug Killer which I have normally found to be effective for most purposes. I have tried that and not totally convinced it has worked. The problem is if the eggs hatch at different times spraying may kill the caterpillars but not the eggs so more appear.
I agree the squeeze technique is effective but if there are lots of them!

[George the Pigman]

Well I have tried a couple of insecticides including a pyrethrum-like one and they still keep on emerging. Picking them off by hand at the moment -there's some every day.These first appeared on seedlings in my greenhouse. I am wary of planting them out in the allotment until I have got rid of them.
Apparently there is a massive epidemic of them this year and they are resistant to most insecticides.
Has anyone tried soapy water on this bug?

[ancellsfarmer]

Further to my previous posts, maintaining a "search& destroy "policy, there are only a relatively small number on each plant and damage currently limited to pierced leaves and chewed stems, primarily on turnip and swede seedlings. Untidy but not crop threatening. Today I noticed several spiders, resembling the Enoplognatha  ovata, bundling up caterpillars in silk and immobilising them. Not tempted to spray at this time,mainly due to the pests being under leaves and the continuing rain showers. Definitely an on-going issue. Any other reports?

[gwynleg]

Hi - dismayed to find that my brassica plants have all got big holes in too - both the ones still under glass and those outside under scaffold netting. Sure enough its the diamond back moth.

Quick rant - I have now got to grow leeks under mesh because they had leek moth infestation for first time last year, and now have to get lots of very fine netting to replace the scaffold netting that has worked so well for brassicas in the past. Its getting to the point that there are very few plants on the allotment not needing covering! Assume its linked to weather changes too.

Rant over - like ancellsfarmer I have also found spiders and caterpillars bound up in silk so hope this is a natural predator that is doing its thing well. Unfortunately not before the leaves are getting very lacey. Is this a widespread problem?

[Crystalmoon]

My turnips have been massively invaded by these moths since being quite small plants (I sowed direct). I thinned them out as soon as the moths arrived which was a lot earlier than I would have done it & the moths seemed to disappear. I have sown a new bed of turnips & the seedlings are just about big enough to thin out now....no sign of the moths on the new bed. The original bed of turnips seem to be doing well even though the leaves are a bit messy with small nibbles here & there. So much rain here in Kent (really torrential heavy rain) that I haven't lifted the nets as I want the plants to have some protection from the rain at the moment but I am considering taking all netting off my turnip beds to see if birds etc will help kill off the caterpillars I am expecting to see very soon. The debris netting has totally failed against these Diamond Back Moths so I am considering buying some extremely fine mesh  for growing Brassicas next year but it is so very expensive. I am wondering if old opaque net curtains would work but wonder if too much light will be blocked by them....any thoughts? xxx 

[Crystalmoon]

Hi everyone, well despite the invasion by nasty Diamondback moths my turnips are maturing nicely, leaves look shabby but the actual turnips are lovely.

[George the Pigman]

Well Crystalmoon -that's a turnip-for-the-book!
I checked all my brassicas on the plot yesterday (an arduous task looking under all the leaves!) and they seem clear. Found one more of the little beggars today on the ones in the greenhouse but none on the ones in the back garden.
Part of the problem is the early caterpillars are minute and burrow into the leaves. They slowly eat the area under the leaves then as they get bigger emerge and start doing some serious chomping. So even though you think you have got rid of them all another one emerges.
I am loathe to plant them out into the allotment until I am totally happy they are clear as they may infest the other ones there.

[gwynleg]

I had thought that the spiders I have found on the brassicas were encasing the caterpillars in silk for later consumption but I read something today that says that this is part of the moth lifecycle. So I went out and picked about 30 little encased caterpillars off my remaining brassica seedlings today. Will have to go and look at the plants already out at the allotment. I also read that they can be easily drowned so watered very vigorously today

[ancellsfarmer]

Gwynleg,
Your source for" spider wrapping is part of life-cycle"?
Mine have been removed from the plant and hopefully eaten!, by a large group of spiders !!I am sure the spiders would have given a death blow prior to wrapping, but if these have been taken off, just to burst out for more destructive chewing, then my russian kale will be done.
If these have swept across the world on the upsurge of oil seed rape (canola), where they can be sprayed but not on our plots, we may need to think further.

[gwynleg]

Hi ancellsfarmer. The source of my information re the caterpillars life cycle is from the BBC: www.bbc.co.uk/gardening/advice/.../identifier.shtml?diamondback_moth

Not sure if that will have made a link? It says "Caterpillars pupate in loosely spun silken cocoons attached to the undersides of leaves. It is the pupal stages that overwinter, although up to six generations can occur each year.'

What do you think?

[ancellsfarmer]

The link did not work for me but I do not think the wrapping  I saw was the work of the caterpillar, but that of the spider(s) seen around several wrapped 'pillars. I doubt that the lifecycle could be reliant upon the chance occurance of such a spider(but never say never!) Although the caterpillars are not currently apparent, I have in mind to capture some for closer inspection in a jam jar- I still have plenty of food for them ,albeit well chewed in parts!
This species of pest , if persistent, will be a major problem to us amateur growers and I am very keen to see how we CAN  tackle it. One thought lies along the lines of yellow gummy strips such as one might use against whitefly in GH. , possibly with an attractant such as mustard, within a hanging lantern as they seem to seek shelter from rain. Back to the laboratory!!