CULT: question - lack of southern borers

Does anyone know why iris borers are not a problem in the south?
Parasites, predators, disruption of lifecycle some other way?

I was worried that I would be battling them from now on after my first
outbreak last spring, but saw no evidence of <any> iris borer activity
this year.

It can't be clean cultivation, because I don't clean up dead foliage.  I
did burn a bit last winter, but mostly in the rows farthest from where I
had found borers.  And I also burned a smallish tangled mess of
blackberries, weeds, monarda, and warm season grasses on the edge of the
irises near one of the locations where the borers were the worst last
spring.

And I don't use pesticides, so that can't be what got rid of them.

I tried very hard to squish every single larvae in the garden last
spring, but would be surprised if I actually got every one of them.
Only about a dozen clumps were affected, mostly in two locations.

Other folks about 50 miles north of me but about the same elevation have
terrible problems with borers every year if they don't spray.

I used to think maybe my late spring freezes killed them, or at least
their food source, but we didn't have any late freezes this spring.  Or
maybe that they couldn't survive our hot dry summers, but it was wet all
last summer.

--
Linda Mann east Tennessee USA zone 7/8
East Tennessee Iris Society <http://www.korrnet.org/etis>
American Iris Society web site <http://www.irises.org>
talk archives: <http://www.hort.net/lists/iris-talk/>
photos archives: <http://www.hort.net/lists/iris-photos/>
online R&I <http://www.irisregister.com>

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