Bulb Pests

[mark smyth]

I've shown this before but this is for Rob - freshly squeezed female Narcissus fly from summer '07

[mark smyth]

eggs

[annew]

 

[mark smyth]

Anne it's great to kill one but better if it's a female

Here are two more photos for Rob. I dont know if I've shown these already. I'm preparing a lecture and came across these in my September folder

[annew]

Look on the bright side, it could be worse - they might do that to people!

[Paddy Tobin]

Little Bas....s!

Paddy

[Armin]

From the sound of it, I think Tony must have had the same problem  with his winter-flowering narcissus as I had with my snowdrops during the incredibly hot Spring weather last year - bulbs dying down very early before managing to build up enough reserves to flower this year.

In my garden, where snowdrop leaves shrivelled in the heat last spring, I now have only about half the number of flowers I should, some normally free-flowering clumps have no flowers at all, and many bulbs that are flowering have gone down in size so much that the flowers are half the size they were last year. Same story with many of the crocus.

Martin,
I agree your opinion and I have a personal thesis that the early heat/drought last spring has also increased the number of bulbs being infested with parasites like narcissus flies. Can you confirm?

 

[Martin Baxendale]

Armin, I don't remember seeing many narcissus fly around last year until after the early disappearance of the snowdrop leaves, and I think I recall Mark saying that the narcissus fly were late appearing, after many leaves had gone.

I don't know, but I suspect the narcissus fly may appear only when they reach the right development, after a set time in the bulbs, and in a set month, so may not be able to emerge early if the weather is warm (like bees, which are just hibernating). So a warm spring and early leaf die-back would be bad news for the fly - but at least some good news for us!

I haven't lifted any snowdrops this year so don't know if there are many narcissus fly grubs in them. I will be lifting a lot for chipping, so will post to say if I find a lot of fly in them. I know my mother found some in her snowdrops last week, but she is at a higher altitude and her snowdrops die back later than mine.

[Armin]

Martin, no - my thesis is opposite!
The new generation of narcissus flies hatching usually eof April to mof May, flying until eof Aug. according to some sources.
If spring wheather is warm and dry, many flies will hatch a bit earlier and at once. Consequently will start breeding/laying eggs by return. Furthermore, the earlier died-back foliage offers an easier access for the hatched maggots to enter the bulbs. Infection rate increases.
In the opposite, if environmental conditions remain bad -spring is cold and wet- less flies survive, hatch and breed. Bulb infection rate is smaller. Sofar my thesis.
I never had any bigger losses of Narcissus bulbs yet before. But when I lifted my bulbs in Aug/Sept. last year I found many rotted with big maggots inside. This supports my thoughts.

[Martin Baxendale]

If spring wheather is warm and dry, many flies will hatch a bit earlier and at once. Consequently will start breeding/laying eggs by return. Furthermore, the earlier died-back foliage offers an easier access for the hatched maggots to enter the bulbs. Infection rate increases.
In the opposite, if environmental conditions remain bad -spring is cold and wet- less flies survive, hatch and breed. Bulb infection rate is smaller. Sofar my thesis.
I never had any bigger losses of Narcissus bulbs yet before. But when I lifted my bulbs in Aug/Sept. last year I found many rotted with big maggots inside. This supports my thoughts.

I see. So you think the narcissus fly grubs develop faster and turn into adults faster in a warmer Spring? Of course the bulb and soil temperature would depend on many factors - if the bulbs with the maggots were growing deep or shallow in the soil, in sun or shade, north slope or south-facing slope, etc. But I see your point. Does anyone know (Anthony?) if bulb-tunneling grubs could do this - turn into adults faster in warmer temperatures?

I try to remove snowdrop leaves as they die, and cover the leaf-holes with compost, to stop fly.

[Maggi Young]

if bulb-tunneling grubs could do this - turn into adults faster in warmer temperatures

Given the fact that temperatures have a huge impact on the gender assignment of things like turtles and crocodiles ( I'm sure David Attenborough explained all this some years ago...) then it hardly seems a great leap of the imagination to suppose that a grub can make growth adjustments by temperature alone.

[Martin Baxendale]

if bulb-tunneling grubs could do this - turn into adults faster in warmer temperatures

Given the fact that temperatures have a huge impact on the gender assignment of things like turtles and crocodiles ( I'm sure David Attenborough explained all this some years ago...) then it hardly seems a great leap of the imagination to suppose that a grub can make growth adjustments by temperature alone.

Then how come human babies don't pop out earlier in summer and later in winter?      I appreciate that environmental factors can speed or slow growth in organisms, just wasn't sure what the balance would be in insect grubs between environmental factors like soil warmth and in-built genetic factors that determine normal development cycles and gestation periods.

My general observations are that the flies seem to appear about the same time every year, regardless of whether it's a warm or cold Spring, or whether it was a mild or freezing winter.

Mark seems to know a lot about the lifecycle of narcissus flie. Can you help us, Mark?

The important thing is to try to remove your old snowdrop leaves as soon as possible, and fill in the soil holes or cover with compost to stop the flies getting in.

[Martin Baxendale]

Oh, and kill the narcissus flies. Swat them! Kill them! Kill them all...kill...killll...them! (curls up in ball, struggling against straight-jacket, and writes 'kill the narcissus flies' on wall of padded cell with foot, like Clousseau's demented boss in the Pink Panther films).

[Maggi Young]

Lot of differences between humans, turtles and grubs, Martin ! That could be an idea for your next book.... I'll only expect a small "finders" fee!!

[Martin Baxendale]

Lot of differences between humans, turtles and grubs, Martin ! That could be an idea for your next book.... I'll only expect a small "finders" fee!!

Yes, as soon as I posted that I thought "Umm, human babies, mother's body temperature constant, daft comparison." But then I was only joking.

Seriously though, Armin's raised an interesting point. Maybe us snowdrop and daff growers could watch out for when  the narcissus fly first appear after this mild winter and report if we see them earlier than usual. It might help prove his point.