REPLY: [pbs] Bulb pests
Sun, 20 Jun 2004 12:18:56 PDT
In a message dated 20-Jun-04 10:42:21 AM Pacific Daylight Time, writes:

> We have a great many feral narcissus here and they host narcissus flies in 
> huge numbers. Many cultivars disappear in one year. I've taken to growing my 
> favorites in large pots and putting these in the shade once the flowers are 
> over. The narcissus fly does not seem to attack bulbs in the shade.

The whole of the Pacific Northwest, with its mild climate, has the same 
problem (as does any place in the world where tunicate bulbs are grown).  When one 
has acres of bulbs, one does what one has to in order to assure survival.  
Simply ridding your stock of this insect pest with hot water treatment assures 
one of only one Spring without their company as the locals will move in to 
picnic on the smorgasbord you've laid out for them!!  One can, of course, dig and 
HWT everything each year.  Depending on how much, where, and when, it is 

I've not found much difference between shaded or unshaded areas with respect 
to infestation.

On the other hand, there are some mechanical methods that one can use to 
protect small numbers of particularly valuable clones.  Plant in beds over which a 
fixed framework can be erected to cover the entire bed for the three months 
+/- while the fly is active.  The white spunbond polyester recommended for a 
degree of frost and insect protection for vegetables laid over this framework 
and lightly stretched is effective -- as long as it hasn't been torn -- and can 
be reused for several seasons.  [Along with this particular material, there 
are several woven, lightweight, UV treated fabrics that one can use.  These can 
be laid over field rows (without supporting framework), as well, I understand, 
although I've not seen it done it this way because efficiency would require a 
substantially different layout of rows and that would have its downside, as 
well, for any amount of acreage.]  They're usually put on around the middle of 
the bloom season and opened to do any hybridizing or collect seed capsules, 
etc.  Whatever is chosen, be careful to make certain the edges are firmly 
weighted down to keep any females from wriggling under; they can be particularly 
persistent.  One has to begin with bulbs free of larvae, of course.  On the other 
hand, if one does get under the cover, they tend to come to rest at the 
uppermost sections in the cool of the night/morning where their dark coloring makes 
them readily visible.  A quick squeeze will dispatch it.

The sad fact of life with this insect and daffodil growers is that the best 
chemicals for combating it (used as bulb dips) are no longer available.  Thus, 
you have your choice -- Spring with few daffodils (or galanthus, hyacinth, 
muscari -- virtually any tunicate bulb, I would imagine) or considerate use of 
effective chemicals according to label instructions and attentive cultivation.

Dave Karnstedt
Cascade Daffodils
Silverton, Oregon, USA
Cool Mediterranean climate; USDA Z 7-8

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