REPLY: [pbs] Narcissus fly
DaveKarn@aol.com (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
cycle.

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
cooker.

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
operation.

Dave Karnstedt
Cascade Daffodils
Silverton, Oregon
Maritime Mediterranean climate
email: davekarn@AOL.com