Leek Moth and Allium Leaf-Mining Fly - The Sequel

Thank you Sid for your very informative blog. Good for you with your persistence and dedicated research! It was great!

Thank you Sid , I will deffinately be keeping my eyes open . , I haven,t noticed anything suspicious yet . except that my leeks haven,t grown very big this year LOL

Well done Sid - I for one would probably have deferred to the experts but you have to be congratulated for knowing what you had seen.

Will this make a difference to growers in your area ?
Not much of an accolade being the first to suffer with such a pest in Herefordshire - wonder if they ll call it Sids bug locally ?

Bb - A dubious honour indeed to be the first case of leek moth the RHS has confirmed in Herefordshire and, presumably, the surrounding counties. Had to have a giggle at your comment - my parents have already been chiding me about this and saying I'll be recieving hate mail from the local allotmenteers! T'is an in-Sid-ious bug indeed!

I'd laugh at that, Sid, except that the subject is not at all funny! Well done for your persistence, BTW. Experts aren't always rght, are they?

Thats clever in - Sid - ious great name for a bug ! Perhaps they should be called something else when they chat to one another and say they re off to take a leek !

Two years ago I grew perfect leeks in our garden near Taunton. Last year the leaves started to shrivel in the summer, but I left them in the ground, hoping they'd recover. By the time I dug up the miserable specimins (mid Autumn?)there was no clear evidence of cause I could see. This year, I lifted them mid August and found that every plant had bore holes high in the leaves , with white or whitish-brown maggot-like bugs chomping away inside. Does anyone know which of the above pests these are? Next year (thanks to above advice) I'll use the same protective mesh I use to keep cabbage whites off my Broccoli.

Hi Adrian - glad you found my blog helful! Leek moth grubs start out tunnelling in the leaves and then move down into the heart of the plant, which eventually turns into a wet, mushy mess. Thankfully I haven't yet had onion fly, so I'm not sure what the effect of those is on the leeks. The easiest way for confirm what you've got is to look out for the cocoons (pictured above) which are unmistakable because of the webbed look - have a look on any structure near your veg plot - a fence, edged of a raised bed, etc.

The cocoons are tiny - 1cm-ish) which means the moths will be tiny too - so I think the holes in your butterfly net will be too big - you'll need to get a finer mesh.

Better luck next year!

I live in Herefordshire and I've had the same pest for 3 years as do many of my allotment neighbours. I didn't know what it was until I just read your blog -- so thanks. In past years it has hit my crop fairly early in the year and I've just dug down throught the middle of the leek and cut the little larvae in half wherever I found them. To my surprise most the leeks made a recovery and I've had half decent crops. This year they came later and I've just done the same thing but I think it might too late in the growing season for them to recover. I wonder if keeping the foliage trimmed might as they won't have as big an area to frolic in.

i ve just joined. my leeks have been decimated by this pest and im in wiltshire. last year i had these cocoons on my leeks but had an ok crop. this year they have ruined the lot. my question is would debris netting keep the moth out

I put this year's damage to my leeks down to slugs - but then yesterday discovered small caterpillar-like bugs nestled inside the folds of the small plants. Most be one or the other of as described here I guess. My onions were OK this year and my leeks were OK last year. Not good!!

Hi There - sorry didn't reply earlier (esp Allotment11) - I've been on holiday!

I'm so pleased to see that my blog has helped people identify their leek problem - makes it all worthwhile. I think the RHS really need to update their records - leek moth is obviously far more prevailent than they think.

Allotment11 - welcome fello Herefordian! lol Yes, I've had it now for about 3 or 4 years. Didn't bother at all with leeks this year. About 2 or 3 of my onions were affected tho :-( Doesn't matter too much with them tho as the grub stays fairly shallow in the bulb and can be dug out and the onion used. Not sure if trimming the foliage would have any effect - remember that the leaves collect the sunshine to fuel the plant's growth.

Hawthorns - I'm not sure what 'debris netting' is.....the RHS recommended ‘Enviromesh’. The moths must be pretty tiny (I have no idea what they look like) so the holes in the mesh would have to be tiny too. A fleece material would be best I would think.

Bygiminee - Leeks and onions used to be pretty pest free and in my experince slugs don't touch them (except where the tips of the leaves touch the soil and rot). Where in the country are you?

Thanks for your information on this pest. I live in north somerset next to the Bristol Channel and have had the moth (as per your photo) for the last 3 years. Don't much fancy using a mesh so would be interested in any other remedy anyone may have. Might have to stop growing them which would be a pity since leeks used to be virtually pest free.

Yes, using mesh is such a faff isn't it! At the time of writing the above, there were pesticides available for commercial growers only. If a pesticide is now available for domestic use, it would have to be a systemic one as I found that the waxy leaves of the leek make anything you spray on just roll of the leaves and not touch the grubs inside. I don't think any other solution has been found so far. I didn't bother with leeks this year, which, as you say, is a great pity. I always used to grow really good ones too... :-(

Have had the same problems with something affecting our leeks at most if not all the allotments in South Cerney.
When you pull a leek it has drill holes in the side and when you unravel the plant there is normally a caterpillar buried deep in the heart. Is it worth leaving these plants in or should we just pull them up and burn them?
What are the pesticides that could be used - probably not any good for this year but a thought for next year.
Onoins and Leeks used to be a guaranteed crop, what with the Badgers, Deer and Blight seems that nothing is safe!!!

Hi Dave - where in the country is South Cerney? Sounds like you have classic leek moth there. In my experience of this pest, there is just no point leaving them in the ground as they tend to collapse and go all mushy and horrid in the center. However, if the infestation is very light and your plants are still alive after the catapillar has dissappeared (gone into the pupal stage) at about this time of year, then you might still get a harvestable crop.

Please see my above comment (of 23 Sept) for info on the pesticide situation. Basically there isn't one licenced for domestic use as far as I can see.

I agree the RHS advice is way out of date. All the allotments on our site in S.Wiltshire are badly affected. Having suffered last year I fleeced until mid-July on the basis that RHS said moth was around May/June. Leeks grew well although watering/weeding is a pain. I then removed fleece, leeks continued fine until early Sept when the tell-tale browning and drooping started and found I had just as bad an infestation as last year only a bit later - I dug up the last miserable remains today! Looks like fleecing throughout the plant's life would be the only solution - as you say this makes them a very marginal crop given the hassle involved.

Thanks for the info Sid. I wondered what was attacking my leeks. I seem to have both pests upon investigating. By the way South Cerney not too far from Dursley, both in Gloucestershire.

Dan - thanks for sharing your experiences using the fleece, which I am sure will be helpful to those set on continuing to grow leeks in spite of the enemy! Yes, the RHS website is badly out of date in this respect.

Dursleyan - oh no! Poor you! :-(

My leeks have been great fro the last few years, but just this week I have seen leek moth damage on my leeks in North Berkshire

Sid - If having trouble getting spray to stick on waxy leaves on Leek just add in a dash of detergent to get the spray to stick on any plant however waxy (same happens on brassicas)

I'll be treating mine with a pyrethroid

Thanks for the useful advice Spudulike!

At last I have found a picture and it is "leek moth" which has destroyed my once excellent crop of leaks. The same has happened to my next door neighbour. We live in Churchdown outside Gloucester so looking at the comments here this moth is spreading north at a considerable pace.
If I were you Sid I would not bother moving to Scotland as with no way available to control them they will be north of the border in the next five or six years.

Glad to have helped, Arfur. Sorry you've lost your crop - is this the first year you've had a problem with leek moth?

I had thought that last winter's hard frosts would have hit the moths hard and pushed them back south....but it seems it is here to stay, sadly.

So far, this blog has attracted 9 comments in September 2009 from people having problems with this pest and trying to ID it. It certainly is spreading at an alarming rate.

I was looking for a possible culprit to my sad brown and slightly slimey leek crop and after Reading this blog it seems I may have found it.

I will check for further evidence to confirm.

Keith from West Berkshire

Hello, just found this site whilst looking for solution to growing leek problem.
One of my customers has had 2 yrs of disastrous leeks, all slimy and collapsing, yuck! I've also noticed her row of chives have displayed similar symptoms at similar time, and they smell very 'oniony'.
Mine, for the first time, are showing signs of what now appears to be the dreaded leek moth. For the sake of 'mapping' them, I live near Taunton, Somerset, it does appear to be a growing problem here. I'll try fleece next year, but was wondering if there's a a way to save my crop which is only just showing signs. Any ideas?

Keith - thanks for your comment - hope it's not leek moth, but sadly Berkshire does seem to be a hotspot.

Jo - This is the first time anyone has said that chives are affected, which makes me wonder if in fact the problem is the onion fly, which the RHS say will attack other plants in the onion family. Having said that, leek moth has also attacked my onion crop, although the damage is not so catastrophic in the onions.

You might get lucky with your leek crop this year. The weather is turning cold, which should cause the catapillars to pupate, which will halt the damage. Good luck with it! Happy childhood memories of Taunton by the way :-)

Thanks Sid, I took a specimen down to local garden centre who said it was leek moth, but that was from looking at damage rather than bug. The creature I saw looked more like a maggot than a caterpillar.
I also noticed a larger green caterpillar munching on another leek, but have seen similar on spinach, so may be a bit of a red herring. Incidentally, at the garden centre they said they'd had loads of people in with leek problems. They are suggesting take up whole crop and burn. As my crop is only slightly affected, I'm loathe to take such drastic action, but also don't want to perpetuate... Hence desire to get diagnosis correct!
I have just found a useful site which has clear pics of different stages of the moth and useful information regarding control. It also mentions chives!

http://www.omafra.gov.on.ca/english/crops/facts/08-009.htm

Bit of a mouthful! Hope it helps anyone...

I have removed all of the affected leaves and burnt them in the woodburner.
My fear is that this and other problems are only going to get worse in the future. Encouraging recycling of garden waste is ok to a point but I feel that there are some things which should never be recycled.
I fear that the rapid spread and intensity of pests and diseases which we are now experiencing are a direct result of recycling all garden waste.
In many areas you will get a visit from the council for burning garden waste so many people put it all in the recycling bin.This material gets recycled and then distributed to a large area. Any pests or diseases not destroyed by the composting process are then distributed with it.

Jo - I think it would be useless now to destroy your leek crop, since I would think that the grubs have already pupated. They don't seem to build their cocoons on the plant itself - they seem to crawl up a wall or fence or something - so, if they've already done that, I see no point in destroying your leeks. Plus, from looking at all the comments from this year alone on here, it's obvious that Leek Moth is very widespread and here to stay, so again i don't think destroying your crop will make any difference to the wider picture. Thanks for the link, I'll have a look!

Arfur - that's an interesting viewpoint! I do my own composting, but of course i have no control over what my neighbours do. One of my pet hates which I have had several rants about on GoY is so-called top soil, and I'm sure that the movement of soil around the country must aid the spread of pests. Maybe not leek moth, but certainly weevils, wire worms and other ground-dwelling beasties. One would hope that Council compost would be sterilised, but maybe that is too much to expect..........?

I live in Chepstow South Wales, on the Bristol Channel close to the Gloucestershire border. All our allotments have had leek moth for about 2-3 years. Rose Clear, the stuff you use against vine weavil and something commonly used to prevent potatoe blight - Bordeau perhaps? - have all been suggested by the local garden centre but i don't think they are systemic.- one of the allotmenteers said rose clear worked for him. People seem to get half decent crops by chopping off the foliage close to the ground. This year I'm going to buy in plug plants which hopefully will be bigger than the ones I sow on my allotment. I think I'll cover them with environmesh but thqt's a faff and I've been told it won't help because its in the ground. Its a shame 'cos leeks used to be so easy to grow.
Leeky

Hi Leeky - yes I know Chepstow....although I admit I am usually just passing through on my way to the Severn Bridges!! You're right I think that all the pesticides you mention are not systemic, although someone above has suggested mixing pesticide with (I think) washing up liquid to make it stay on the surface of the leaves (as the problem I found was that the pesticides simply rolled off the waxy leaves and the catapillars are safely hidden within the leaves). When I started this blog back in November 2008, my research said that there was no insecticide available for gardeners, although there was one pesticide approved for commercial use only. It might have changed by now, but I'm not aware of anything new on the market.

That's interesting that people are chopping the foliage down to the ground - my own experience is that the catapillars make their way to the young leaves in the centre of the plant and once those collapse, the plant is a gonna. I wonder if chopping the plant down BEFORE the catapillars reach the centre of the plant actually interupts their life cycle - i.e. removing the little b*****s while they're still living in the older leaves before they get to the centre of the plant and kill it? Obviously this method is not going to result in the healthiest/biggest leeks, but it's still a step in the right direction!

I don't agree that 'it's in the ground' by the way. The larva pupate the same way as a butterfly or moth and they seen to like to hang their cocoon on a vertical surface. My onions have been slightly effected by leek moth too and last autumn, because of the wet weather, I lifted my onions and hung them in the greenhouse to dry off. The catapillars emerged and built their cocoons on the wooden window frames of my greenhouse - sometimes going up quite high. I don't think they pupate in the soil at all, but if they did I would have thought that thorough digging and rotating your crop would deal with that.

Thanks for your information and insight Leeky - better luck with it this year!

Thank you for sharing your experience with us. I have had a problem in allotment near Wolverhampton this last year with in my early sown and transplanted leeks whereas my later ones were ok. The symptoms were slimly dead outer leaves and I found little reddish brown chrysalides lower down in blanched stem as I pulled the outer leaves off. I never saw any silk cocoons. I think my problem is possibly the Allium Leaf Miner since RHS point out this is prevalent in West Midlands. . I shall attempt protection of leeks with fleece or net this year and see if things improve. I will not be able to persuade my fellow allotment holders to take any action although many of them had similar symptoms but yet I will observe with them if any differences attributable to Physical protection. But I should bear in mind this winter, unlike the several previous ones, has had long periods of sub-zero temperatures which may help to alleviate the problem for this coming season.
Last year I stopped growing onions and garlic because of crinkling in leafs and bulbs did not store well at all despite some later apparent recovery of plants. This problem started some tears ago on neighbouring allotments. I attributed this to nematodes but fellow allotment holders insist to continue.

Sorry to hear of your problems Graeme. From your description I think what you've got is the Allium Leaf Miner. I too am hoping that the cold winter will have killed off these pests, but I fear they are here to stay. I plan to keep my leeks covered over this year. The onions will have to brave it!

This has all been helpful but no help really. Help!! Lost all my leeks last year for the first time here in Swindon. So did people on other allotment sites in town. I'm going to try planting in blocks with french or african marigolds around. I'll let you know.

Pickle 23 May 2010

Thanks Pickle - let us know how you get on - the marigolds might just fool them!

Its now mid june and i have found two leeks that have been eaten by the dreaded moth! I have pulled them up and burned them, but am worried that they will be inthe others, just not obvious. do you think i have caught them in time?

my late husband and i have grown leeks for about 34 years in the same garden last year was my ffirst experience of leaf moth they decimated my crop i live in wiltshire am trying again this year I have them covered and have sprayed with bug off but i dont know how the end result will be

Hi Robster and Download - thanks both for commenting on my blog.

Robster - Unfortunatly I suspect your other leeks will also succum. Some very helpful comments and suggestions have been made in the comments here - have a read and give them a go and then come back here and let us know how you got on! Good luck!

Download - Hopefully you'll have success if you're using a fine-woven cover. However, with regards the spray, that doesn't seem to have any effect as the solution simply runs off the waxy foliage and does not come into contact with the grubs inside the leaves. Annoying isn't it - I too had been growing really good leeks for years until the dreaded moth struck, so I know how you feel :-(

Hi Sid and others.
I've read with interest all your comments on the leek moth as mine are being eaten as we speak!! I live in Hereford and they've only been in the allotment for 3 weeks as leeks seedlings I grew in my greenhouse. I too thought leeks were immune to pests but this is the 3rd year it's happening and although I used enviromesh last year in the early stages of growth, as soon as I took it off, they got attacked. I will try roseclear today and see what happens. I actually saw one of the maggots on the inside of the leek!!!

Hi Sid and others. I couldn't see my comment on the site so I wrote another one.Now I see it so have to edit the second one!! Am not very expert as this blog thing, sorry.

Hello Sid and all other grower with the Leek / Onion problem
Just wanted to let you know that we have grown leeks very succesfullly for about 8 years and love the leek and potato soup they make. Last year we had to burn our whole crop of leeks because of the leek moth - it was terrible, and had devastated the crop before we realised what it was.

I know this might sound crazy but we bought a polytunnel 3m x 2m, early this year specifically to grow the leeks in - (could'nt find anything else that would keep the moth out but let me in!). We have been careful when watering to keep the door zipped up so the little critter wouldn't creep in - so far so good although the leeks are still very small. However - I found a coccon on the kitchen surface after we had pickled our shallots!! this sent me running out to the garden to check the onions - knowing that the moth also likes them, and to my horror they are attacking our onions! Found cocoon on and larvae in the leaves. Have just checked the leeks in the poly tunnel, a leaf or two look a bit suspect but couldn't find any evidence.

Has anyone else grown leeks in a poly tunnel?

Any further advice, tips etc would be gratefuly received. Oh forgot to say we are in Dorset

Froggie - Hi there, nice to hear from a fellow Herefordian! I'm in Ross Rd - I wonder which allotments you are at? Sorry to hear your leeks have succumed too - I'm just wondering why you took the enviromesh off? I haven't tried it yet so I'm interested to hear how you found it. Do you think it cut out too much light or affected growth in any other way? And, yes, it's inside the leaves where you'll find the maggots :-(

Currant - I like the sound of your polytunnel!! Unfortunately I haven't got the room for anything like that tho. My only concern would be the possibility of the moths getting in through cracks around the door, etc. Good luck with it tho! I too have found cocoons in the kitchen in previous years as I tie my onions up in plats and (because I think they look pretty) I have them hung on the wall in my kitchen! They do attack my onions, but I find they don't devastate them like the leeks. They tend to attack the leaves mostly. But when they do attack the bulbs they don't burrow straight in, but rather just tunnel a short distance just beneath the skin, so it's easy to cut that bit off when you use the onion. I just have to make sure I identify which ones are affected and use them first as I doubt they'd store too well.

Just one bit of further advice: if you think there may be grubs in your leek leaves, do make sure you deal with them - remove the affected leaf completely, or try to locate the grub and squash it in situ. Otherwise, the grub will go down into the heart of the plant and destroy the plant.

I came across this site while looking for information about Leek Moth and am thrilled to discover so many other addicts all in one place and so keen to talk about gardening and send in so many wonderful pictures. I am in danger of spending more time on here than outside.
I have had Leek Moth for 3 years, here in Somerset. This year I was determined to beat them. I grew some good healthy plants in a pot and planted them out and kept them alive through the drought. But due to a combination of vanity ( we had our garden open in the local garden trail) and then forgetfulness, I did not get the fleece on for 2 weeks.
Of course when I came to put it on there were the tell tale signs. Leaf damage, piles of green droppings and collapsing leaves.Then the maggot inside. I whipped out all the damaged ones and replaced them with spares kindly donated by a fellow gardener. Now the fleece is on and so far they look ok.
Does anyone know how these moths operate? Apparently there are 2 breeding seasons so I was caught by the first. Do you think any eggs laid will have hatched by now? Of course they could have been laid in the pot before I planted them out. I forgot to protect that. Are the eggs laid in the leek or on the ground? Can they survive on the ground? Any advice gratefully received.

Hello Sid
Thanks for your comments and advice. Unfortunately though | pulled all the onions up before I read your response! The are a fairly decent size though, so not all lost. I dont know if I should cut the stalks off or leave them to dry as normal - does anyone have any thoughts?

Marshmallow - I think that the moth can overwinter in debris and start again next year! I cant see anyway out of the problem except for physical protection. Our veggie patch is getting full of mesh and cages!

Anyway I agree with you, this is a wonderful site and also came across it whilst searching for info on the leek moth.

Hi Marshmallow - glad to hear you're enjoying the site and, yes, it's highly addictive!! If you visit www.inra.fr/hyppz/RAVAGEUR/6acrass.htm I think this answers all your questions. Currant is right in saying that they overwinter in debris on the ground.

Currant - you're welcome! That's a good point about whether to cut the leaves off or not...of course the normal thing would be to allow the leaves to dry off naturally (and I plait mine), but does this help the moths to survive and would it cause them to migrate from the leaves into the bulbs? I don't know the answer, but I suspect the leaves drying out would indeed drive them towards the bulbs :-(

Ha ha...yes, my veggie patch is starting to look like that too - full of mesh and cages - what with the birds and the butterflys and the moths!! lol

I've just come across some info on another site - there is a product called Bayer Greenfly Killer that contains deltamethrin which says on the lable that it can be used on leeks - now I've never seen greenfly on a leek...I wonder what effect it would have on leek moth?

Thanks Sid. That has answered most of my questions.
I went out last night and found some more of the little pests so I squashed as many as I could find but most of my leeks are still ok. Fingers crossed.

I've just been picking through my onions that have been drying for the last fortnight and have found about 60-70% are affected by the cursed leek moth here in Chippenham, Wilts. This is my first year growing onions so the wastage is soul-destroying.
What can I do with so many onions with a couple of holes in them? Are they ok to go in the compost bin?
I have also found a few examples of a long brown-bodied fly that looks a bit like a flying ant in amongst the drying onions with the leek moths. Any ideas what that might be?
I have been squishing as many of the moths, pupae and larvae as I can find, and there are quite a few.

Hello Sid and all leek moth sufferers
I have just visited the website you mentioned, and I now think that I had better cut off the stalks from the onions - thanks very much for the info. Also a few other sites say that you can store onions by cutting off the stalks to about 1" and storing in mesh or nylon stockings - think I will try that, perhaps I should have cut the stalks off as soon as I saw the beasts?!? - I dont know why you should leave the stalks on, I only do it because I have seen others do it, and yes I plait mine as well (because they look pretty) but dont know what the real benefit is!

Growing in the polytunnel along side the leeks, is White sprouting broc and Curly Kale, as they also get attacked by caterpillars - (nothing worse than finding one on your plate!), however I have found two huge caterpillars on the broc, and another on a leek stalk, all pale green. The ones on the broc had a back a bit like a mountain range and the one on the leek was smooth. The door is always zipped up even when I am in there and the windows have mesh on them - how do they get in?? - its a constant battle and I hate killing them. The broc growing outside the tunnel is daily attacked by the white cabbage butterfly, but her eggs are so visable and in such close proximity that removing them is not a problem, but I never see those eggs on the Curly Kale - only the caterpillar.

Hello Sid
We live near Barnstaple in North Devon and lost all my leeks last year as I did not know what to do - this year I thought I had got away with it as we watered onion fly nemotodes into the raised bed where we grow the onions and leeks but on Thursday I found the telltale little holes but not so badly as last year's infestation. I could not find the grubs so maybe they have gone? I have started to use the leeks just in case and have made a lot of leek soup and frozen it but guess I will try fleece next year and leave it on for the whole season as it seems thats what has worked for others. They will be in a different raised bed next year again of course (we have 3) but obviously the little beasts are somewhere nearby. I destroyed all the damaged crop last year but could have missed one or two maybe?
Sarahpeter
6 August 2010

We have raised beds, 1.5 meters wide- last years leeks were decimated- and virtually useless- the dreaded leek moth?? This year we have coveed them with fleece, held off the crop by wire hoops from day of planting- now crop is pushing the fleece up from the sides, leaving a small gap just above ground level- will the moths get in, at this stage (mid august)- no sign of damage so far.
Beds are constructed of wooden sides, so I use a commecial staple gun, with small pieces of polythene damp proof, to anchor the fleece- has worked successfully so far- but now crop is outgrowiung the fleece- does anyone know of a wider fleece than 2 meters. n Malvern, Worcs

Grow leeks between rows of celeriac. Both leeks and celeriac do better than when grown separately. And there is less damage from leek moth.

I have used two strips of fleece to cover my leek bed and have fixed it to wire supports with washing pegs. They have been very sucessful even though it has been windy. The two strips overlap quite a lot and are pegged at the top and down the sides. Happy to report the leeks look ok. Wondering when it is safe to take off the fleece.