We are often told to use lime sulphur for a
dormant spray in the winter, but the rationale behind its
use and the proper method of application are often not
clear.
The following was gleaned from an article that I recently
read in one of the Japanese magazines. I found it
interesting and thought that it would be useful to summarize
it here. The article was written in response to a reader's
questions about the use and effectiveness of lime sulphur as
a dormant spray in the winter.
Lime sulphur is effective for controlling scale and red
spider mites among insects, and for a number of diseases as
well. Hence it is useful across a broad spectrum, but will
not be an effective control for aphids. Something else will
have to be used for them, but there is little concern for
aphids in the winter.
Lime sulphur may be applied from the time that leaves
fall until two weeks prior to the beginning of the following
spring. Spraying will be less effective against scale if
done when the temperature is below freezing. Spraying may be
done twice, once in early winter and again prior to the
beginning of spring, but if done thoroughly and carefully,
once in mid-winter will suffice. The spring spraying is
usually for those trees that missed being sprayed in early
winter because they were being prepared for shows.
Spraying lime sulphur solution gives trees a whitish cast
that often lasts for three or four months. Trees that will
be displayed should not be sprayed prior to that time unless
they are beech, maple, or birch, in which case spraying will
enhance the already white color of the bark. (Editor's note:
Do not spray flowering apricot.)
Trees with fresh pruning cuts should not be sprayed with
lime sulphur immediately, as it will or may be absorbed into
the wood and harm the branch or the entire tree. Similarly,
lime sulphur should not be applied to new jin or shari for
at least a month after they have been created.
Containers that are especially valued should be covered
with plastic or old newspapers prior to spraying to avoid
discoloring, and this should not be removed until the
solution has dried.
One should not worry about how long the effect will last
since a good, thorough application will kill off scale
entirely for the winter and will serve as sufficient
prevention.
Dormant spraying of lime sulphur solution in the winter
is critical for the year-round health of the trees in your
collection, and should be performed carefully and
thoroughly.
From Mr. Umehara's article in the November 2002
newsletter, here are recommended dilutions for lime sulphur
dormant spray:
|
Tree Type
|
Ratio
|
When
|
|
Deciduous
|
20-1
|
Half the foliage still remains
|
|
Conifers
|
30-1
|
End of November, beginning of December
|
Pearls of Bonsai
Wisdom
