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nafex - Re: [NAFEX] Apple stem borer

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  • From: "HDessureault" <inter.verbis@videotron.ca>
  • To: <nafex@lists.ibiblio.org>
  • Subject: Re: [NAFEX] Apple stem borer
  • Date: Thu, 25 Jul 2002 14:10:24 -0500

To Nafexers,
This sums up my experience to-date with tree borers.
After many years of problems with apple tree boring insects, I was able to
overcome the problem with the help of some of the members of this list who
were faced with the same problem.
You will remember that there was extensive discussion on wood borers on this
Membership List last year. It seemed to be the consensus that the best
method was to insert a wire down the hole to impal the culprit. As I
remember, Phillip from Maine even proposed a perfect wire made from piano
string.
The hole of wood borers is noticeable at the base of the tree because you
can see a little pile of rusty colour wood dust coming out of a needle size
hole. This is caused by the larva chewing its way in the sapwood between the
bark and the wood and enlarging its gallery to fit its growing size.
My solution is to dust a spray of organic insecticide made from pyrethrum on
the hole and push a metal wire as far as it will go in the tunnel to kill
the insect. I think Claude Jolicoeur was the one to suggest this in detail
and it works.
I was able to test the organic insecticide to be effective on one of the
borer I had extracted with a knife. The borer dies of suffocation when in
contact with pyrethrum dust. I used the wire, sometime being successful on
the first attempt and sometime having to repeat the operation a few days in
a row before the activity stops which is the proof that the ennemy has been
neutralized.
When I first understood the problem which has puzzled me for a few years (I
am embarassed to admit), I used to dig out the insect with a knife, but it
does too much damage to the tree and is not necessary as the wire is
perfectly sufficient to do the job. When I dug out the larva with a knife, I
found two types which I identified as the flat-headed borer mostly and a few
round-headed borer. My orchard was in real trouble as only one borer can
cause the death of a tree, when the tunnelling happens to be going around
the tree. They usually tunnel in a general vertical pattern. But
nevertheless the tree is very weakened by it.
I now know that the colour of the wood dust coming out of the tiny hole is
not the same for the two larva above mentioned. The flat-head borer dust is
rusty colour while the other one I believe gives out a darker brown trail of
dust. Regardless, they are both extremely harmful and must be destroyed.
When the larva has become large enough, it moves in the root system under
the tree where it causes more damages and becomes an adult, a black flying
insect (a beetle apparently), which comes out of the ground (I am not sure
but that is my impression that the beetle does not travel in the tunnel to
come out...) and infest more trees by laying eggs on the surface of the bark
near the base.
I found an adult at the same time as larvae last year in early August which
seems to indicate that these borers don't have a typical seasonal cycle like
some other insects that infest our fruit trees. Regardless of its age, it
seems to spend the winter in the root system of the tree.
I destroyed every larva that I could find last year, and I found a
relatively very small number this year end May, early June which I promptly
destroyed. Since, there are no more traces and I periodically inspect the
base of all my trees ready to intervene. I have not seen any signs lately
which leads me to believe that if the problem is left unchecked, the
population increases. But if the larvae are systematically destroyed, then
the problem becomes occasional.
I have lost a few trees to this insect in the last few years. In the Spring
the tree does not leaf out and when you pull it out, you find that there is
hardly any roots left and a large section is decayed and reddish brown.
One tree, in which I had found three flat-headed borers last year did not
survive.
So at this point all I can say is do not despair, you need only a good wire
and some assiduity for a while.

Hélène, zone 3-4





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