Narcissus Fly: When is it safe?
Fri, 08 Aug 2008 09:41:00 PDT
On 6 Aug 08, at 17:03, Roy Herold wrote:

> I had a terrible time with narcissus fly getting into my pots of cyrtanthus
> when they were outside last summer (2007), so this year I put them in a
> coldframe covered with a screen (window type). Thinking that the danger of
> fly infestation was passed, I took the screen off a couple of weeks ago,
> mainly because flower scapes were running into it. 
> Did I take it off too soon? Or could I have removed it much earlier, and 
> if so, when?

Here (Victoria, BC, Canada), narcissus flies first appear in early May when we 
finally start getting some warmth in the air. They're on the wing until July, 
and I'm pretty sure I've seen a few even late in July.

They're easy enough to control with insecticidal drenches; they're just flies. 
But since the only insecticides available now are non-persistent, you have to 
keep drenching and drenching and drenching for several months. I can't be 
bothered, and I don't like the idea of pouring lots of insecticide (even if 
it's non-persistent) on my garden, so I don't bother. Imidaproclide is too 
toxic to other insects to be considered, even if it were readily available here 
for insecticidal use.

Screened frames are definitely the way to go if your area is infested with 
narcissus fly and you want to grow amaryllidaceous bulbs they attack.

You can also wrap subject plants in Reemay cloth or even kitchen cheesecloth.

I'm surprised the pesticide industry hasn't come up with a pheromone attractant 
for narcissus flies so they could be trapped.

Rodger Whitlock
Victoria, British Columbia, Canada
Maritime Zone 8, a cool Mediterranean climate

on beautiful Vancouver Island

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