Narcissus bulb fly

[Lesley Cox]

Getting there though. The large n fly seems to vary in its colouring quite a lot.

[annew]

Having a look at some images of bees on google, it seems that flies have much larger eyes than bees. Could this be used as ID if close enough?

[mark smyth]

there is no confusing a bumble bee and a Narcissus fly only when the first small bumble babies are flying. Narcissus flies dont hover

[Gunilla]

I did not know the Narcissus bulb fly existed before reading about it here on the forum.   Good thing I did read this thread because last week I saw the fly in my garden and killed about 15-20 in two days. 
Today I found a soft narcissus bulb with a fat grub in it so I guess the Narcissus fly must have been in my garden earlier in spring. 
Narcissus bulb fly
Bulb with grub

[Rodger Whitlock]

Today I found a soft narcissus bulb with a fat grub in it so I guess the Narcissus fly must have been in my garden earlier in spring. 

That grub grew from an egg laid last spring or summer.

I wish some clever biochemist would determine what, if anything, is the scent that lures the narcissus fly to the bulbs. If it could be produced artificially, we could bait these horrible insects and perhaps greatly reduce their numbers.

Here in Victoria, it's a hopeless situation because the climate agrees so well both with narcissus and with the predator, and waste places often have feral daffodils that grow in spite of the fly and act as nurseries for it. Many of these feral daffodils are evidently famous cultivars from perhaps a century ago that have long since been superseded and perhaps lost in cultivation.

[mark smyth]

Gunillas grub is very big to have been laid during May and June but adult Narcissus fly have stopped flying now in Europe. This could be a late developing grub.

[Gunilla]

Well, the fat grub on my photo is not developing any more 

[Paul T]

Given how much trouble the Narcissus Fly can cause, how is it handled commercially?  Do they spray with something, or just net the whole area as the bulbs start to head towards dormancy (i.e when the flies are likely to be laying eggs)?  I can find very little information on it except from a home gardener perspective, yet it must be a big problem for bulb growers on a commercial scale.  Does anyone know?  How does the Netherlands deal with them?  Giles article (fascinating read, thanks Giles) doesn't seem to sound like there has been that much found by way of chemical means either?  Defoliation sounds a bit extreme to me, as it would likely affect the flowering for the next year wouldn't it?  If you left it late enough not to, then wouldn't the egg laying already be done?

Gunilla,

I found one here last summer for the first time (grub in a bulb, not the fly itself), so they're here now too.  I have to find out more myself now on how to treat them, because going out with a fly swat just isn't an option when you're working full time.  There must be some method of treatment that can be used?

[Rodger Whitlock]

Given how much trouble the Narcissus Fly can cause, how is it handled commercially?  Do they spray with something, or just net the whole area as the bulbs start to head towards dormancy (i.e when the flies are likely to be laying eggs)?

Two methods: hot water treatment, which kills the grub; and insecticides, potent ones that have been outlawed in many countries.

There seems to be a myth that narcissus flies are like vine weevils, immune to most insecticides, but that's not true. They're just stupid flies and nearly any standard insecticide will kill them. The trouble is that almost no persistent insecticides are available to the home gardener these days (in British Columbia at least) and since narcissus flies can be on the wing for months (here in Victoria BC, from early May to the end of July), you either have to use a persistent insecticide or reapply any number of times.

Some 20 or 30 years ago there was a gal with a small commercial daffodil operation at Duncan BC, 30 miles north of Victoria. The story went that once DDT was off the market, she used chlordane, and when that went off the market in BC, she found a mail order source in Quebec.

I've heard many times that you can reduce the depredations of the narcissus fly by backfilling around the dying foliage with very fine, dry sand. This prevents the newly hatched grub from creeping down to the basal plate of the bulb. I don't know if this method works.

[Susan Band]

Here is what DEFRA (English Agri department) has to say about them. They have done a study on them, in conclusion they haven't found much to control them since the pesticides were removed from sale but it does give a lot of info on the larvae, eggs etc.
http://randd.defra.gov.uk/Default.aspx?Menu=Menu&Module=More&Location=None&Completed=0&ProjectID=7941
You have to click on the 'Final Report'
Susan

[Paul T]

Rodger and Susan,

My sincere apologies.  I thought I had posted in here a Thank You to you both for your responses.  Either I am mistaken, or else this was another of my "disappearing posts" that seem to be happening from time to time.  I read both your responses at the time and was very thankful for them.  They confirmed a lot of what I had been able to find out myself.  Hopefully the DEFRA site is not closed for too long, as i wanted to make a few references to it in an assignment I am currently completing for my Horticultural Studies, but the site is closed for maintenance.  Murphy strikes again. 

Could I possibly ask that any of you who still have information available on what was previously (or is still used in some countries where not banned) used to combat the Narcissus Fly, please let me know what chemicals were used?  I am particualrly interested in the active constituent.  There are no chemicals at all registered for use in Australia, so I am trying to find out what was used overseas up until they were banned.

Thanks very much in anticipation of any help.

[Rodger Whitlock]

. . . what was previously (or is still used in some countries where not banned) used to combat the Narcissus Fly

IIRC, Methoxychlor applied every two weeks as a soil drench used to be the recommendation.

I've been told (iow, don't quote me) that methoxychlor, supposedly a biodegradable chlorinated hydrocarbon, invariably contained DDT as an impurity and much of its insecticidal virtue was due to the DDT. Truth? Slander? Urban legend? I do not know.

If you can group your amaryllids in one bed, a cover of cheesecloth or anything similar will suffice to keep the flies at bay.

[Paul T]

Thanks Rodger.  From investigations, the cover does seem to be the most useful method of prevention, and the hot water treatment is the usual method of "treating" a possible infesting of the bulbs.   Your confirmation is good, because it isn't suggesting something else I haven't come across (if you know what I mean).  

Every bit of information is helpful as this is a fairly major assignment, due in the next couple of days.  I've just been struggling to find the chemical side of things, which is why I asked for further information.  I realise that so much of this will vary from country to country as well, which is why the wide readership of these forums are so extremely useful to break down the borders and find out information we can't find.  Do any countries still have any chemical recommendations in place, or does anyone have any other recommendations for previous chemical treatments?

Thanks again for your help, Rodger.

[mark smyth]

Dursban was the best one in the UK until it was banned.

"A water dispersible granule containing 75% w/w chlorpyrifos. A broad-spectrum insecticide controlling many pests of agricultural, horticultural and forestry crops."

Other products contain chlorpyrifos.
"Chlorpyrifos is a toxic crystalline organophosphate insecticide that inhibits acetylcholinesterase and is used to control insect pests. Trade names include Dursban (home and garden uses) and Lorsban (agricultural uses)."
http://en.wikipedia.org/wiki/Chlorpyrifos

Acetylcholinesterase
"Acetylcholinesterase, also known as AChE, is an enzyme that degrades (through its hydrolytic activity) the neurotransmitter acetylcholine, producing choline and an acetate group"
http://en.wikipedia.org/wiki/Acetylcholinesterase

[Gerdk]

Paul,
Chlorpyrifos, the active ingredient in 'Nexion Neu' is avaiable here for application against larvae of flies in cabbage, onions and carrots.
But as usual it is allowed only for use in the crops mentioned.
I don't know if there are similar restrictions in countries outsite Germany or the
European Union.

Gerd