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Austrian (Pinus
nigra),
ponderosa and mugo pines are most susceptible to Dothistroma needle blight. The disease, which is also
called red band needle blight, can cause permanent loss
of needles and, if left untreated for many years, may
lead to the death of the tree.
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This fungus diseases causes browning of needles along
the length of the stem. Unlike
Diplodia tip blight which
attacks only new growth, this disease affects both the
previous and current year's needles. The needles turn
brown from the tip and have a reddish brown band part
way down the needle that is distinctive of this disease.
The ends of the needles may break off leaving a blunt
stub. Eventually, the entire needle turns brown and
dies.
Cause:
This disease is caused by the fungus,
Dothistroma (Scirrhia)
pini. It usually begins to show up when trees get large
and old especially if they are crowded together too
closely or are otherwise under stress.
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Plant species of pines that are resistant to this
disease such as white pine (Pinus strobus).
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For new plantings, use native pines such as Eastern
white pine and red or Norway pine. There are also a few
resistant varieties of
Austrian
Pine that are available.
For mature trees, two applications of a fixed
copper or
Bordeaux mixture type of
fungicide are recommended to
control Dothistroma. If these materials are used, the
first application needs to be in mid-May to protect the
previous year's needles. The second application should
be made in mid-June to provide protection for the new
needles.
Maintaining a spray
program for several years may help to bring back even
severely infected trees. If the disease has progressed
too far, however, it may not bounce back even with the
recommended applications.
Severity of infection may be minimized by keeping trees
in a moderately vigorous state of growth. Proper
fertilizing and watering may help minimize stresses.
Allowing enough room for root growth and expansion over
the life of the tree is also important.
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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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