REPLY: [pbs] Narcissus fly
Sat, 25 Jan 2003 06:48:01 PST
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<<> Can you elaborate about your homemade bulb cooker that you use to control 
the Narcissus fly and what exactly you do?  It sounds like Narcissus may not 
always be a bulb you can safely plant in the ground in the Pacific Northwest 
and leave.  <<>

As with so many parasites, the Narcissus fly seems to leave completely alone 
things of little value.  Of course, as Murphy would have it, the most 
valuable things seem to fall victim to it.  I have driven around the 
Willamette Valley extensively in the Spring and have often been amazed the 
quantity of feral daffodils one will find.  Apparently, at one time many 
years ago, the ubiquitous yellow trumpet one sees growing everywhere in 
Spring was planted in bulb growing fields for cut flowers and dry bulb sales. 
 Those fields are now often pastures.  The bulbs that were missed when the 
fields were dug have since multiplied into great swaths of yellow flowers 
visible from some distance.  And, as I previously mentioned, fence rows and 
gardens everywhere each Spring sport enormous quantities of daffodils.  So, 
despite the Narcissus Fly, daffodils survive and bloom each Spring and, for 
most people I suppose, it's of little concern.  While it may not concern 
them, these plantings are reservoirs for the insect.  When the flies emerge 
in Spring, they mate and the females start looking for $50 daffodil leaves -- 
yours -- on which to lay their eggs!  The egg is laid at the base of the 
leaves where it hatches a few days later.  The larva crawls down the leaf to 
the bulb where it enters at the base (usually) to begin feeding.  It remains 
in the bulb until early Spring when it exits the bulb to pupate in the 
warming soil.  The adult fly emerges a short time later to begin the next 

While the life cycle of this insect indicates parasitism of tunicate bulbs, 
the bulb is usually not entirely destroyed (if it's large enough).  Rather, 
with elimination of the apical meristem, the secondary meristem sprouts and, 
while the main growing point is destroyed, it is replaced with a number of 
smaller bulbs that take a couple of years to reach blooming size and, once 
again, become food for the next generation.

Daffodils are prone to several parasites.  The best defense, in this case, is 
a good offense:  very carefully examine any tunicate bulb you intend planting 
on your property to make absolutely certain that it is free of disease and 
parasites.  I can guarantee you the cure will always involve more effort than 
prevention!  Of course, ordering from reputable firms is the first step.

Hot water held at a certain temperature for a specified length of time was 
developed by an English researcher named Ramsbottom to combat the bulb and 
stem nematode then decimating English bulb stocks in the 1920s.  114 deg. F 
for three hours is said to rid the bulb of this parasite.  One has to be 
extremely careful with this process, however, as this temperature is 
borderline between curing or killing.  Slightly lower temperatures and 
shorter immersion time, i.e., 112 deg F for 1.5-2.0 hours in early-mid August 
will kill the fly larvae burrowing in the bulb.  The bulbs have to have been 
dug and kept warm and dry for several weeks after being dug before this 
treatment is attempted as it can damage the newly formed bud that will only 
form after the bulb has been held at 70-75 deg F. for six weeks.

Certain chemicals are often added to the water, in particular to deal with 
nematode infestations and Fusarium.  A common one is formaldehyde, now banned 
in many places.  The replacement would seem to be peroxyacetic acid.  To aid 
in heat penetration, surfactants are also added and to control foaming that 
occurs when the solution is agitated, antifoaming agents are also added.

"Bulb cookers" range from professional units that are used to sterilize 
bottled products to large watering troughs, down to something that has been 
called the "garbage can bulb cooker."  This was developed by Marie Bozievich 
(a noted daffodil grower) and seems to work fairly well.  One starts with a 
large garbage can (often plastic, but galvanized will provide greater 
rigidity).  One needs to figure out how to insulate it to aid in maintaining 
a uniform temperature throughout the bath.  A thick layer of very firm 
Styrofoam larger than the base will work to prevent heat loss from the 
bottom.  The can itself can be wrapped with several layers of Fiberglas house 
insulation (wear gloves, eye protection and long sleeved clothing as broken 
pieces of the insulation fibers can be very irritating).  It's wise to have a 
valve mounted near the bottom of the can and enclose the whole thing in a 
wooden frame that can be permanently insulated and covered over.  With the 
valve in place, water can easily be drained from the container without 
soaking the insulation.

One needs a heater, usually a hot water tank heater of some sort will work.  
The can has to be fairly tightly lidded to maintain an even temperature.  A 
circular piece of thick marine plywood is best and three holes are made in 
it.  The lid is then varnished (with marine varnish) on both sides.  The 
central hole requires a cylinder of heavy hardware cloth be formed (and that 
allows at least one inch between its wall and the propeller) and fastened to 
the underside.  This will contain a "drill bit" that has been formed from a 
rod on which a small propeller has been welded.  This fits into a device to 
turn the rod (a variable speed electric drill mounted on the topside of the 
lid and whose speeds can be set and left) at a desired speed.  This 
circulates the water in the can.  Another cylinder will contain a thermometer 
and the third will contain a thermostat.  The heater is set into the can, 
also protected from the bags of bulbs; it's best if it is set near the bottom 
of the hot water bath.  The thermostat can be set into the lid or run down 
the inside of can and protected from the bags of bulbs it will eventually 
contain.  Do not scrimp on the instruments, as they must be of high quality 
and accurate.  Temperatures outside of the treatment range will kill the 
bulbs, often a greater loss than the cost of the instruments. 

As with many things, there is the best way and then various modifications 
that compromise the process but are cheaper.  Caveat do-er!!  I've seen this 
process used with chest type deep freezers modified with the necessary 
equipment down to large Styrofoam picnic containers heated with aquarium 
heaters, a thermostat and an aquarium air pump to circulate the water and 
maintain a uniform water temperature.  Irrespective of what is being used, 
the important thing to remember is this: the water must be maintained at a 
uniform temperature throughout the container for the specified time, or there 
will be problems.  An accurate thermometer is essential.

Circulation of the water tends to be the biggest problem with the can 
cookers.  One hard and fast rule is don't overload the unit!  I used several 
bricks on the bottom of the can to keep the bulbs off the bottom and aid in 
circulation.  Ultimately, I made a cylinder that reached to and sat on the 
bottom for ease of use and stability.  The rod also contained more than one 
propeller welded on.  This created considerable centrifugal force keeping the 
water at the required temperature without creating pockets of overheated or 
underheated water.

This cylinder was set into the can, the bags of bulbs loaded into the 
preheated water (a quick way is fill the container directly from a hot water 
heater), the lid set into place, the agitator rod inserted into the drill and 
the drill mounted into place on the lid.  The last steps were to connect the 
thermostat and heater and to insert the thermometer into its protected cage.  

Loading of the unit will substantially lower the temperature.  Timing cannot 
start until the temperature stabilizes at the desired treatment temperature.  
One way to shorten the interval is to soak the bags of bulbs for a couple of 
hours in water kept warm and to which a surfactant has been added.  When the 
cooker is ready, load the bags of warm bulbs directly from the bath into the 

Once they've been treated, the bags of bulbs are removed, drained and 
immediately hung in a shaded airy place to cool and dry; fans help.  Planting 
should be done within a few weeks after treatment for best results.  In many 
areas, daffodils will root at the merest hint of moisture.  I have dug 
daffodils in the heat of August (especially poeticus and Division 9 hybrids) 
only to find they had thrown the new set of roots.  This is one of the 
reasons I am death on weeds because I have found the leafy biennial types, in 
particular, to concentrate moisture in the soil, whether by condensing the 
dew or from transpiration I don't know, but under the right conditions, it 
can be a problem.  Plus, weeds need to be controlled for all of the other 
reasons one does so!  While absence of weeds makes spraying more effective, 
it also makes it easier for the female fly to find a set of daffodil leaves 
particularly to her liking.

Hot water treatment is an effective method for controlling bulb fly.  While 
the process may appear complex, like any process, with organization and 
practice, it becomes routine.  However, its effect will last only one season, 
as treatment does not preclude re-infestation from outside of your growing 
area.  It is actually easier to spray (with a contact insecticide, e.g., 
Dylox or Dursban) several times during fly season or to make beds that can be 
sealed off with fabric from the late bloom period to senescence of the 
leaves.  Some apocryphal evidence seems to indicate that systemic 
insecticides are effective.  For these things to be effective, the chemical 
would have to be resident in the bulb tissue (as the newly hatched larva does 
not begin eating until it reaches the bulb itself) and that would mean, I 
would think, that treatment would have to be frequent during the growing 
season and at least one year prior to the anticipated damage. 

I've never encountered the bulb and stem nematode (extremely difficult to 
eliminate; actually, the best cure is to abandon everything, sell the 
property and move!!) but have used this method to eliminate bulb mites from 
stocks.  I now use sprays almost exclusively for control of bulb fly, 
primarily for its ease of use and effectiveness and due to the size of the 

Dave Karnstedt
Cascade Daffodils
Silverton, Oregon
Maritime Mediterranean climate

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