Onion/leek fly
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Brooklynodog
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- Location: Somerset
For the last two years I have suffered with onion fly on both my leeks and onions, loosing the whole crop in 06, and most last year. What do you advise? Should I give them a miss this year? I try to be as organic as possible, and used old washing up water on them which seemed to help, but inevitably the little blighters took over. Do any chemicals help?
I've also been troubled with this pest, so this year I am building an enviromesh frame to sit over my crop. Some say you can cut down the foliage and your leeks will regrow pest free. I have never tried this so cannot say how effective it is. Oh, and don't forget to rotate your crop!
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Brooklynodog
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- Location: Somerset
Can you elaborate about the enviromesh frame, Ive not heard of that? Does rotating crops really help with airborne pests like onion and carrot flies, as myth would have it that they can "smell" crops from a long way away?
The Leek moth and carrot fly will over winter in the soil so yes rotation and strict hygiene is very important.
Destroy infected plants and don't compost.
I have grown both leeks and carrots very successfully under enviromesh and horticultural fleece.
Beryl.
Destroy infected plants and don't compost.
I have grown both leeks and carrots very successfully under enviromesh and horticultural fleece.
Beryl.
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Brooklynodog
- KG Regular
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- Joined: Mon Jan 28, 2008 4:06 pm
- Location: Somerset
Is there anything that you can treat the soil with to kill these pests, hopefully organic? Incidentally, I have never had a problem with carrot fly (touch wood!)
I don't know about carrot fly but there is nothing for the leek moth.
Beryl.
Beryl.
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Brooklynodog
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Thanks Beryl. Is leek moth the same beastie as what I call Onion and/or leek fly then?
You may find this helpful.
This is part of a letter received from RHS in 2002
'The damage that you have noticed on your leek plants has been caused by the caterpillars of a pest commonly known as the leek moth. This is a local occurrence in Britain, being mainly found along the east and south coast of England, although it does sometimes occur further inland. Where it is found it can sometimes be very troublesome and make the growing of leeks and onions difficult. It has two generations during the summer with the larvae being active during May and June and again between August and October. The larvae feed initially as leaf miners in the foliage but as they grow larger they bore into the stems of leeks and into the bulbs of onions. Once the caterpillars have penetrated the deeper tissues of their host plants it is very difficult to reach them with insecticides. When the larvae have finished feeding they emerge from the plant and spin net-like silk cocoons, usually on the foliage. Pupae of the late summer generation are present during September to October and the adult moths emerge during the latter month. This pest overwinters as adult months which seek sheltered places during the autumn.
It is worthwhile examining the foliage on your leeks to try and detect these pupae which can be destroyed by hand removal before the adult months emerge. Next year you should watch out for signs of leaf mining beginning on your plants during May and August. There is currently no pesticide available to amateur gardeners for use against pest on leeks. In the absence of pesticides, gardeners now have to either tolerate the damage cause by the leek moth or they can try and protect the plants by growing them under the cover of as horticultural fleece. This is a finely woven material which allows light and water through but will exclude most pest, including the egg laying females of the leek moth.
The only pesticide which is currently approved for the use on leeks for leaf miner control is nicotine. This is not sold in small amateur packs and is only available to professional growers. If nicotine is to be effective it needs to be applied when signs of leaf mining are first seen. There would be no point in spraying your plants now as we are at the end of the larval feeding period and they will be currently emerging from the foliage in order to pupatei'.
The following article was written by John Trim in the National Vegetable Society Quarterly Bulletin. Vol.10 part 4.
The Leek moth is becoming increasingly frequent problem in Southern England and it can also attack onions. This moth is of local occurrence in Britain, being mainly found along the east and south coasts, although it does
sometimes occur, further inland. Those of us who have been troubled by this pest have found that the growing
of leeks has become exceedingly difficult. The moth produces two generations during the summer. The larvae are active during May and June and again between August and October. They feed initially as leaf miners in the foliage but as they grow they bore into the stems of the leeks and into the bulbs of onions. Once the caterpillars have penetrated deep into the tissue of the plants it is nigh on impossible to reach them with pesticides. When the larvae have finished feeding they emerge from the plant and spin net like silk cocoons, usually on the foliage. Pupae of the late summer generation are present during September to October and the adults emerge during the latter month. This pest then over-winters as an adult moth in sheltered places. Control - Examine the foliage of the plants regularly, and if you spot damage on the leaf you can usually track down the larvae and destroy them. Pay special attention to your plants from May onwards. There is currently no pesticide effective against the moth that is available to amateur gardeners. An alternative, and very effective, way to protect your crop is to grow under fleece or, even better Enviromesh. The latter is more expensive but will last many years and has the advantage of allowing air circulation and natural rainfall through to the crop. It will exclude most pests, including the egg laying females of the leek moth. I have known some exhibition growers who have installed ultra violet lights that electrocute the moths when they attempt to land. If all else fails and your crop has been badly infected you can always cut the foliage off your leeks and they will re-grow, albeit somewhat smaller. But do not try this with onions. But, realistically, if you live in an area where leek moth is prevalent the only way forward is to provide some form of physical barrier to prevent the female moth reaching the crop.
Beryl.
This is part of a letter received from RHS in 2002
'The damage that you have noticed on your leek plants has been caused by the caterpillars of a pest commonly known as the leek moth. This is a local occurrence in Britain, being mainly found along the east and south coast of England, although it does sometimes occur further inland. Where it is found it can sometimes be very troublesome and make the growing of leeks and onions difficult. It has two generations during the summer with the larvae being active during May and June and again between August and October. The larvae feed initially as leaf miners in the foliage but as they grow larger they bore into the stems of leeks and into the bulbs of onions. Once the caterpillars have penetrated the deeper tissues of their host plants it is very difficult to reach them with insecticides. When the larvae have finished feeding they emerge from the plant and spin net-like silk cocoons, usually on the foliage. Pupae of the late summer generation are present during September to October and the adult moths emerge during the latter month. This pest overwinters as adult months which seek sheltered places during the autumn.
It is worthwhile examining the foliage on your leeks to try and detect these pupae which can be destroyed by hand removal before the adult months emerge. Next year you should watch out for signs of leaf mining beginning on your plants during May and August. There is currently no pesticide available to amateur gardeners for use against pest on leeks. In the absence of pesticides, gardeners now have to either tolerate the damage cause by the leek moth or they can try and protect the plants by growing them under the cover of as horticultural fleece. This is a finely woven material which allows light and water through but will exclude most pest, including the egg laying females of the leek moth.
The only pesticide which is currently approved for the use on leeks for leaf miner control is nicotine. This is not sold in small amateur packs and is only available to professional growers. If nicotine is to be effective it needs to be applied when signs of leaf mining are first seen. There would be no point in spraying your plants now as we are at the end of the larval feeding period and they will be currently emerging from the foliage in order to pupatei'.
The following article was written by John Trim in the National Vegetable Society Quarterly Bulletin. Vol.10 part 4.
The Leek moth is becoming increasingly frequent problem in Southern England and it can also attack onions. This moth is of local occurrence in Britain, being mainly found along the east and south coasts, although it does
sometimes occur, further inland. Those of us who have been troubled by this pest have found that the growing
of leeks has become exceedingly difficult. The moth produces two generations during the summer. The larvae are active during May and June and again between August and October. They feed initially as leaf miners in the foliage but as they grow they bore into the stems of the leeks and into the bulbs of onions. Once the caterpillars have penetrated deep into the tissue of the plants it is nigh on impossible to reach them with pesticides. When the larvae have finished feeding they emerge from the plant and spin net like silk cocoons, usually on the foliage. Pupae of the late summer generation are present during September to October and the adults emerge during the latter month. This pest then over-winters as an adult moth in sheltered places. Control - Examine the foliage of the plants regularly, and if you spot damage on the leaf you can usually track down the larvae and destroy them. Pay special attention to your plants from May onwards. There is currently no pesticide effective against the moth that is available to amateur gardeners. An alternative, and very effective, way to protect your crop is to grow under fleece or, even better Enviromesh. The latter is more expensive but will last many years and has the advantage of allowing air circulation and natural rainfall through to the crop. It will exclude most pests, including the egg laying females of the leek moth. I have known some exhibition growers who have installed ultra violet lights that electrocute the moths when they attempt to land. If all else fails and your crop has been badly infected you can always cut the foliage off your leeks and they will re-grow, albeit somewhat smaller. But do not try this with onions. But, realistically, if you live in an area where leek moth is prevalent the only way forward is to provide some form of physical barrier to prevent the female moth reaching the crop.
Beryl.
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Brooklynodog
- KG Regular
- Posts: 93
- Joined: Mon Jan 28, 2008 4:06 pm
- Location: Somerset
Thanks for your time Beryl, looks like I`ll have to invest in some enviromesh if I want to continue growing onions and leeks (which I do).