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CULT: Borer--for Bob

In the beginning, Bob Axmear, interested in borer control, wrote

<< I do what the book say and clean up the old foliage in the  fall and this
spring  >>

Bob, since you are admirably concerned about the environment, and not
interested in chemical prevention of this pest, I thought I might return to
your original question and make a couple of comments. First, earlier on this
list Clarence Mahan, than whom few know more about borer,  informed us that
one study of borer habits indicated that the moth lays its eggs a good deal
later than we had come to believe. In Virginia it is usually late November.
The thought is that if one delays Fall cleanup until after that time, then
one is more liable to get the eggs on the debris, but if one is premature one
forces the moth to deposit them in a foliage crevice or on the rhizome where
they are optimally situated for spring hatch. It is also very important to
clean up very well in the Spring. People used to sprinkle kerosine or light
straw on the iris bed and set it very briefly aflame. In lieu of this, superb
garden sanitation will help a lot.

Other points to bear in mind: The borer moth is a shy dark-headed nocturnal
creature which is not attracted to light. It prefers crowded plantings,
neglected plantings, and plantings in the shade, and there is some evidence
that evergreens attract it. Site your bearded iris bed accordingly, and sift
the soil for pupae when you prepare it. We don't know as much about the life
habits of the pest as we might. There is some thought that the first warm
spring day over 72 triggers hatch, an idea to which I don't give much
credence in this part of the world because we often have temperatures in that
range quite early, but one which might be of value to you. I'd personally be
on the lookout for borer activity when you first see aphid activity. You can
learn to recognize the little wretches eating their way down the inner
leaves, leaving jagged edges and slimy trails, and a borer that is squeezed
in the leaf is a dead borer. There is one more idea I will pass on, although
it is my own and utterly untested. I have become very interested in the idea
of spraying the bed quite late in the fall, after the final clean-up, with a
light dormant oil spray such as Sunspray. This is a refined paraffin that is
applied in very dilute water solution and is used to smother the
overwintering eggs of other insects such as scale, etc. The environmental
repercussions are not grave, and I have found it to be very effective.
Whether it would work on borer, I don't know. But in your situation, I'd try
it. I'd wait until the foliage has pretty much gotten hit by frost and all
insect activity has ceased. There is also some thought that beneficial
nematodes may work, but others say that the borer is not vulnerable when in
the soil. 

I hope this will be of some value to you.

Anner Whitehead, Richmond, VA  Zone 7
Henry Hall  henryanner@aol.com 

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