Fellows and fellas tree growers,
To follow up on the question I put to the
group two weeks ago, here is a report on my borer, the flat head borer. The
presence of this particular borer, infesting some of my trees, can be detected
by a tiny little pile of reddish brown wood residue on the ground under a
pin size entrance near the base of the tree. After having destroyed an area
under the bark, relatively large as compare to their size, the white larvae
eventually dig a gallery towards the roots where they become adults and where
they do extensive damages to the root system in the process. You have to get the
larva out as quickly as possible and that involves unfortunately cutting out
the damaged areas with a knife in search of the beast. I had as many as
four in one single tree of a 2 1/2 " diameter. I found two the first day, once I
knew what to look for, and another one the next day. A few days later, I
observed more reddish sawdust and found another one. All this in a 2 1/2 "
tree! You have to get them out as soon as possible. The more time they spend in
the tree, the more damage they do. Had I not noticed, I am sure that those
4 borers would have done enough damages to condemn that tree. All in all, I had
to dig a large area on the side and underneath the tree where I followed
one larva. The roots of that particular tree were chewed and
destroyed (attacked from two sides) in a north south plane and the hole
that I had to dig underneath the tree allowed to see the light on the other
side. Fortunately, the roots on the east and west side of the tree were
healthy and solidly anchored as I was able to observe as the day was unusually
windy, which gives me hope for the survival of the tree.
Claude Jolicoeur, who provided very useful advice
on the subject, had mentioned that in some cases pushing a flexible wire
through the hole could work to kill the bug inside. While not being a
solution for every circumstances since the larva changes directions, in one
instance where I would have had to cut live bark to get to the larva, I used the
wire instead and it worked. No more sign of activity, since.
The larvae are easily killed by rotenone. The
adults don't like it but seem more resilient and they are able to run away.
Unfortunately, it is a contact insecticide and dusting it on the bark or at the
hole or even squirting it in the hole diluted in water is not sure to work as
there is an extensive amount of wood excrement between the surface hole and the
larva. Once you get to the larva, there is no sense using the rotenone as it is
quicker to kill the larva directly.
I continue to check my trees every day for a late
larva, but so far so good. In total, I had five trees attacked by these larvae
and most had 1, some 2 and one had 4 larvae in different spots on the base
of the same tree!
I had dug out a small dead tree recently, that
had started to leaf out and had dried up, and all the root core was reddish
brown and rotten. No doubt that the borers were at work last year. I had no idea
then of the problem and I failed to notice.
The only good news is that these larvae, after the
initial chewing of a relatively large area given their size, dig a gallery
down and don't girdle the tree. But then, if they are many or if they
attack the tree every year...
I intend to fix the damage that I have created with
the knife by covering with a clay and a bit of cement mixture that is more
liquid and not as hard as cement and I apply it thinly with a brush. I fill in
the holes and gaps where insects have a tendancy to lay.
I also intend to paint the trunk of all my
trees with lime this year, ahead of the flat head borer laying season, to see if
it will stop this borer from laying its eggs.
A friend explained a method that he has seen of
covering the base of the tree with a tube of corrugated cardboard a foot tall
early August and removing them early winter to burn them... That might
work, but I tend to shy away from labour intensive methods.
The beauty of the lime applications is that it is a bit like killing
many birds with one stone. Borers are my worst insect problem ever, and what
is worst it took me a few years to identify the problem. As I mention,
I first though it was collar rot. I insist on this because, while
not being very knowledgeable relatively speaking on the subject of apple
tree growing, I have been at it for a while and I am very interested and usually
very attentive to what is happening. And yet, it took me a long time to get to
the bottom of this situation. Luckily for me I did not follow the advice of
cutting down the first trees that showed borer damage as I would have been
forever cutting down trees thinking it was collar rot... One has to be more
weary of drawing quick conclusions.
I also have another type of borer which penetrates
the tree through one hole and comes out another. If you squirt some water into
the hole, you can see it come out the other hole. This borer seems to prefer
bigger trees as I have only observed these holes in 4" tree and larger. The
holes are the size of a pencil.
I have not identified the culprit yet.
I suspect for the moment a shiny long worm that is shiny charcoal grey
and has circular rings at regular intervals all along the body. At this
time of year, this particular funny looking creature is curled up in the
soil at the base of the tree (not a cut worm). Is anyone familiar with
these...
I guess you can say that I am
currently studying the ennemy.
Hélène, zone 3
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