Leek moth

We have been struck by the vile leek moth. Last year we raised 82 perfect leeks on plot 201, and this year we were well on the route to similar success when suddenly every single leek was attacked. It’s a bit of a bugger, because there’s no recovery from late summer leek moth predation.

In the interests of science (rather than harvest, as this year’s crop is definitely a goner) I did some research and found out that:

There are two waves of attack - one in spring and one in late summer, both result from caterpillar behaviour. The second wave (which got to our leeks) is far more damaging than the first one.

The caterpillars start by tunnelling into the leaves, and then down into the stem and bulb, causing large areas of damage which then rots, causing total devastation. The adult moth overwinters in plant debris and the female lays eggs in spring that hatch about a week later. It’s the moths from the spring hatching that then emerge to destroy plants in August and September.

Treatment is simple and preventative – clear away and preferably burn debris after harvesting leeks. Dig over the soil to disturb overwintering moths and pupae. Destroy severely infested plants in spring. Protect remaining plants with fleece. Try not to play out leeks until May (ha!) to avoid the worst of the laying season. Encourage birds, bats, hedgehogs, frogs and beetles who will all variously much away on the moths, caterpillars and overwintering pupae.

And if only I’d known that earlier in the year, I wouldn’t be staring at ninety of these collapsing leeks …

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Posted by The Allotment Blogger on Wednesday, October 20, 2010


Anonymous Emma said...

My dad's leeks were attacked this year as well, I think the problem has been worse than usual. I forgot to plant any!

October 20, 2010 at 5:00 AM  
Anonymous allotment4you said...

I had no idea there even was a 'leek moth' so I am glad that you have highlighted this for me and the preventative measures...thanks.

October 20, 2010 at 9:06 AM  
Anonymous Damo said...

Sorry to hear that the leek moth sounds bad, not something I've seen. That said my leeks are up the road at a neighbours so I need to check how they are doing.

October 21, 2010 at 10:00 PM  
Blogger The Allotment Blogger said...

Emma - it's better to forget than lose the lot!

Tanya - I didn't know until this year either.

Damo - apparently it's moving from the South of England northwards, so you may not have it yet.

October 25, 2010 at 8:07 AM  
Anonymous Louise said...

Like you I've grown perfectly good leeks for years on the allotment. But this year has been a disaster - all of them have slowly rotted away! I've been doing research and like you have found that cleaning up and then covering the crop with fleece are recommended.

October 16, 2011 at 2:02 PM  
Blogger The Allotment Blogger said...

Louise, I've also been told that you can rub leeks with petroleum jelly as soon as you see the first sign of leek moth and it stops them - no idea how though! It all sounds a bit peculiar but I shall give it a go next year, for research purposes.

October 24, 2011 at 2:58 AM  

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