Narcissus Bulb Fly - Merodon

Mary Sue Ittner
Tue, 30 Oct 2007 08:15:17 PDT

I wasn't sure I had a problem here in Northern California, but I do. It's 
my understanding that they go for the big bulbs first so that you may not 
recognize the problem as there may be some offsets surviving. The ones I've 
discovered in my garden and my greenhouse have been in Cyrtanthus mostly. 
It's happened enough now that if I see the foliage going down at a time of 
the year when it isn't expected (or in something that is usually evergreen) 
I dump out the bulb and look and sure enough it is mushy with a grub 
inside. At first I thought I was just watering too much. I really love the 
Cyrtanthus that they love too and I'm not sure what I want to do as I'm not 
going to use pesticides on a regular basis. One suggestion has been to 
cover the bulb when the foliage is drying off, but in my cases there was no 
foliage dying back and the leaves are tall and any way of protecting the 
plant would definitely take away from your pleasure in looking at it.  It 
reminded me of seeing the bulb collection at UC Santa Cruz Arboretum when 
they were struggling to have a collection because of squirrels, deer, etc. 
The whole collection was in a small screened enclosure where it was 
impossible to see and enjoy most of the plants when they flowered.

The biggest disappointed was when they took out my large Paramongaia. I had 
thought I wouldn't be able to grow it and had many years of finding what it 
needed since my climate is a challenge for it. Then one year there was a 
beginning of a flower scape and I was delighted since I really had given up 
hope. But then the scape started to look sickly and shrivel, then the 
leaves, and sure enough when I dumped it out, it was being consumed from 
the inside. A few offsets on the outside of the pot seemed unaffected.

We've talked about this in the past. Dave Karnstedt provided a lot of 
information since it was a problem for him with all the Narcissus he grew 
so a search of the archives would provide more comments. We know it occurs 
in Ireland since the link on the wiki to the picture of the fly and a close 
up of the larva if from Mark Smyth and since he writes about Galanthus, 
this must be a genus they like too.

I recently repotted two pots of Cyrtanthus mackenii (evergreen) which 
normally blooms a number of times a year and is evergreen when I realized 
some leaves were dying and the plant wasn't blooming. Both pots had been 
getting pot bound and I knew I needed to divide them. When I dumped them 
out, I discovered the biggest problem was the grubs eating many of the bulbs.

Mary Sue

More information about the pbs mailing list