re: Phermone Traps for the Borer
Ian Efford wrote: "Has anyone considered putting out baited
moth traps during the evenings during the weeks (July-August
for Ottawa?) when the moths are flying..." and there have
been other notes on this thread recently.
Phermone traps have been used for a couple of decades for several
commercial fruit crops. For example, the codling moth trap is
used in apple orchards quite extensively (and is commercially
available, at least in Canada).
However, the use of such traps is misconstrued. They are not used
to eliminate the pests themselves, but to identify when the pests
are out and breeding.
Once a moth is caught in the phermone trap, the clock starts. After
a given number of days (which varies from species to species), the
pesticides are applied. This kills the larvae before any significant
damage can be done.
The key point: If you don't see the moth in your phermone trap,
you don't spray or soak! (In the case of apple pest management, this
can have the effect of cutting down the number of pesticide spray cycles
from as many as ten (10!) per season to three or four. We are talking
extremely serious money here.)
In the case of iris borer, there are several issues to be addressed
beyond the development of an iris borer phermone trap:
First: The egg has to hatch if this procedure is to be effective.
Given that the iris borer lays eggs in the fall which hatch in the
spring, there is not a great deal to be gained by knowing when the
borer emerges. If, however, the moth emerges in the spring, there
is a great deal to be gained. But more importantly...
Second: Knowing when the moth has emerged is not sufficient. We live
in different climatic and geographic regions. I have not seen the
life cycle of the iris borer described in the detail necessary to make
full use of a phermone trap.
How much time elapses between the time the larvae pupates and
the moth emerges?
How much time elapses between the time the moth emerges and
How much time elapses between the time the moth mates and
How much time elapses between the time the eggs are laid and
By 'time required', I do not mean measurments in calendar days, but in
degree-days (d-d). In simple terms, this is the number of degrees C
(or F) over a base temperature (say 10C/50F) for a base period (days
in this case). The subject is much more complicated.
For example: If the borer eggs are laid in the fall, when is the
earliest date the eggs will hatch? Ian Efford in Ottawa will have the
borer eggs hatch in mid May, Kathy Guest in E.Aurora (N.Y.) will have
them hatch in late April...we think. But if we know that the eggs hatch
after 300 d-d C (540 d-d F), then we can ignore the calendar and rely
on our respective departments of agriculture to notify us how many
degree days have passed. Both Ian and Kathy will spray at exactly
the same time...in degree days.
So, the number of degree-days for each of these steps need to be
determined. Once they are determined, then we could identify the optimal
time to apply the pesticides. The additional precision provided by
the phermone trap is useful, but not essential. It becomes essential only
when conditions allow two generations within a single growing season.
This is an extremely precise method with excellent benefits to those
who wish to make the effort and conduct the necessary research. The number
of applications of cygon (for example) could be reduced from 3-4 to 1-2.
On the other hand, we could just apply the chemicals when the leaves
are ten to fifteen cm (four to six inches) above the ground...and keep on
applying them with the respect those chemicals deserve.
As an aside, the necessary d-d detail might exist; if anyone can provide it
I would geatly appreciate receiving it.
And finally, if the phermone traps were sufficently inexpensive, one trap
per clump would probably suffice.