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re: Phermone Traps for the Borer

  • To: Multiple recipients of list <iris-l@rt66.com>
  • Subject: re: Phermone Traps for the Borer
  • From: sandy_ives@cbc.ca
  • Date: Fri, 12 Sep 1997 15:07:46 -0600 (MDT)

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 
	mates?  
	How much time elapses between the time the moth mates and 
	lays eggs?  
	How much time elapses between the time the eggs are laid and 
	hatch?  

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.

Sandy





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