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Ever walk into the yard
in late spring to be confronted with a large number of
otherwise healthy looking maple leaves covering your
grass? Well, the odds are good that this is the work of
a tiny insect called the maple petiole borer. The
petiole is the stem of the leaf and the larvae of this
critter does its work by eating inside this stem.
The insect is a sawfly
which deposits its eggs near the base of the leaf
petiole in the early spring just as the foliage emerges
from the buds. When the eggs hatch, the tiny larvae
begin to feed inside the petiole. By the time they are
done feeding and ready to pupate, they have hollowed out
the leaf stem. It is so weakened that it will drop off
in the breeze leaving a darkened area at the point of
separation.
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As mentioned
previously, the key symptom is the dropping of a
relatively large number of otherwise healthy looking
leaves. The black area where the petiole breaks is
also a strong symptom. If you take a close look at
the petiole, you will find that it is hollow.
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A somewhat long shot
method for preventing or minimizing this problem
would be to persistently clean up and destroy all
the leaves as they fall to the ground. The larvae
will usually crawl into the ground in order to
complete the next step in their life cycle.
Preventing them from doing so, MAY help to minimize
next year's crop of petiole borers.
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Even in severe cases,
maple petiole borer causes little damage to an otherwise
healthy tree. Most trees have the ability to replace
lost foliage early in the season so this problem is
mostly one of aesthetics.
Even if you wanted to
treat for this problem, it would be quite difficult. The
insecticide would have to be on the petiole pretty much
the day that the leaf opened. Once he eggs are inside,
most
insecticides would be ineffective. So...just rake
up the leaves and put them in your compost bin. The tree
will be just fine...unless it has other, more serious
problems.
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Note: We
have provided some general information and
observations on this topic aimed at the home
gardener. Before you take
any serious action in your landscape, check
with your state's land grant university's
Cooperative
Extension
Service for the most current,
appropriate, localized recommendations. |
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