Narcissus bulb fly

[mark smyth]

I saw two Narcissus fly in the garden last week

[Paul T]

Thank Mark and Gerd.  Your info has been added. 

[Rodger Whitlock]

What surprises me (but I *am* easily surprised) is that no one has looked into developing a scent lure for the narcissus fly, either the scent of dying narcissus foliage or the scent of a female seeking a mate.

The one time I tried growing chlidanthus (in a pot), narcissus flies (both large and small) attacked and destroyed the bulb before it even had a chance to flower. One has to wonder if chlidanthus smells extra tasty to the flies and whether it could be used as a bait for them. Perhaps surround the pot with a wire screen enclosure with one-way entrances similar to those used in wasp traps.

[mark smyth]

Good idea but would they make enough money? Only serious bulb growers would want them. Joe Public who grows Tete-a-Tete and loses some every year wouldnt buy it - I dont think. Commercial growers rely on hot water

[mark smyth]

This is how you shouldnt leave tasty leaves in the garden to tempt the fly

[Paul T]

Mark,

Literature seems to vary..... do the flies lay on dying foliage, or dead foliage?  Or is it that the early fliers start on the dying off foliage and then there are more for the next couple of months that then hit the dead foliage?  I'm assuming that as there are flies around any of the warmer months the old foliage is hit as well?  How far after flowering do you find that the first flies appear?

[mark smyth]

I see them in my garden on green and yellow leaves. They also sample other leaves and stems. I dont know if they taste the leaves or smell them

The dead leaves belong to a well known N Irish gardener who never clears away the leaves

[Paul T]

Mark,

But are your observations always after flowering, or are there flies already laying eggs while flowering is taking place?

[mark smyth]

Never while flowering and always when leaves are past their best. May and June for us so November and December for you

[Paul T]

Thanks Mark, that fits in with what I had worked out.  So the Narcissus Fly you saw this week were probably from something other than Narcissus, looking for other Amaryllidaceae?

[mark smyth]

No I think these would have been late to hatch. While repotting yesterday I found a Muscari that had signs that a grub had been eating it over the winter

[Paul T]

Well according to some of the stuff I've read, Narcissus Fly have been reported to feed on Hyacinths.    I had thought they just would have been flies that had been using a host on a different seasonal schedule.... surely if Crinum are being used as a host then eggs can be laid at any time over the summer months while there is greenery?  I suppose the egg laying time isn't the issue though, is it?  It is the temperatures that trigger the hatching of the flies from the pupae.  Given hwo strange everyone's weather seems to have been this year it isn't surprising that they're confused.    Enough people certainly are.

 

[mark smyth]

Paul they only fly for a month or six weeks and any Amaryllid is a target. When active I find them in the green house most days inspecting my Nerine sarniensis

[Lesley Cox]

Unfortunately Paul and Mark, the larger narcissus fly is active in warmer gardens, at least here in NZ, for up to 4 months. I have seen them laying in October and as late as January, which is logical, considering how early Galanthus leaves are dying off, compared with later Narcissus or other amaryllids. My usual practice is to scruff up the soil where the leaves are dying away and make sure the holes left by the shrinking leaves are filled.

[Rodger Whitlock]

Repotting Acis longifolium today, I found my biggest bulb with a *&*#*@! narcissus fly grub (the larger) protruding from the bottom. The entire basal plate may already have been destroyed by bacterial or fungal rot consequent on the grub's filthy excrement. I split the bulb in half, washed out the wound, and dusted the cut surfaces with sulfur in the hope that it's a fungus that the sulfur will bring under control. The grub I foolishly squashed before remembering that a photograph would have been of interest here.

At the current stage of its development, the grub was about the size of a grain of rice and had not yet hollowed out the bulb.

A reminder then that narcissus fly attacks all Amaryllidaceae: narcissus, acis, leucojum, hippeastrum. And it will attack bulbs of other families in a pinch: I've seen it in a hyacinth bulb.