CULT: Iris Borer In AZ

I am sorry I did not keep a copy of the email I had sent out earlier about the 'whatever-it-was' chomping on my iris rhizome.  But as promised, I was going to let you all know what it was.
 
I thought that it was an iris borer since the thing ate part of the leaf at the ground level and worked his way down into the rhizome itself.  However, with the help of some experts we have come to find out that it was a CUTWORM. 
 
Normally, cutworms do not attack irises.  So, what is it that caused this one to have such a voracious appetite to eat the iris???
 
I have a few theories on this, for this was NOT an isolated incidence, unfortunately.  My friend Judy has had the same devastation occur in her garden which is 5 miles west of me.  While over at her house I was checking the irises in her beds, and about 20% of them had been chewed on, however there doesn't appear to be any sub-surface feasting going on (hopefully). 
 
Judy's garden has many irises and other flowers, where my iris bed only contains irises - but it used to contain 12 ten-foot tomato plants, along with flowers and other veggies.  Since there is plenty of other flowers growing in Judy's garden, I suspect the cutworms ate them rather than burrow into a rhizome for food - but time will tell as rot will set into the cuts. 
 
Neither one of us EVER remember any pest eating our iris leaves, and neither do many other locals I asked.  Therefore, something has changed.
 
This year however, was a strange one.  Phoenix had a very mild summer in comparison, and we had El Nino to thank for that I'm sure.  Also, we hardly had as many white flies due to all the rain, and when one part of the ecology changes, so do all the rest.
 
I would venture to say that due to the weather changes this year, our population of cutworms may have increase, or they might have become more aggressive in the same manner as bees get.
 
I consulted many gardening books about how to rid the garden of cutworms.  There are some organic methods I found to control cutworms: placing a stiff paper collar around the plants, and the use of chicken manure, oak-leaf mulch, damp wood ashes, crushed eggshells, or sharp builder's sand.  Neither one of these seems like a very good idea for irises, for many of them would cause rot.  Therefore, I saw no alternative to going chemical on the critters.
 
The chemical method I found to control cutworms is described as this:
 
In the evening water the flower bed and wait for the water to suck into the ground.  Spray the ground around the plants, but not the plants themselves with Diazinon.  As the Cutworm emerges for its nocturnal feeding, it will come in contact with the poison which will kill it. 
 
Another method described the above, but then after spraying with a slightly stronger solution of Diazinon, water the garden again and the chemical will be carried to the root areas of the plants. 
 
Repeat every 2 weeks during fall.
 
I opted to spray the ground and see if that takes care of the problem.  We'll see how it goes...so far so good.
 
Patrick Orr
P*@Hotmail.com
Zone 9 Region 15
Member: AIS, TBIS, SDIS (local)
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