Aleppo pine blight, which has no known biological cause, is
particularly severe this year. Tree owners noticed problems with their
Aleppo pines beginning about Thanksgiving, 2002. By January 2003, the
problem became severe. It is especially prevalent on old, established trees
with high value. Young trees appear to be resistant to it. It also appears
occasionally on Elderica pines and Canary Island pines, but the problem is
most prevalent on Aleppo's. Why? No one knows. |
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Aleppo Pine Blight, Jan 2003 |
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So what could the cause be? Discussions with Dr. Jean
Stutz at Arizona State University and Ron Ykema of the State Agriculture Lab
have offered a number of possible "new" biological agents. Could it be
Xylella the bacteria-like organism that is responsible for Ash decline and
Pierce's disease in grapes? This organism is widespread in ornamental plants and
there are hundreds of known symptom-less species. However, no conifers have been
listed as carriers of Xylella. Another suspect is Cylindrocaron which
people at BBI Labs have isolated from the roots of some affected trees. Are these
specimens deficient in some type of mycorrhizal fungus that leads to the
plugging of xylem vessels that lead to blighted stems? Who knows. Other
possible culprits are mites. We have noted that the needles of affected
trees that begin to decline show small chlorotic spots that resemble mite
damage and we have seen mites crawling on our specimens when we examined them
under the microscope. No webbing is present and mites are certainly known to
be pests of other conifers.
So what causes Aleppo pine
blight? We at Artistic Arborist are now embarking on controlled,
experimental studies to see if there is a way to overcome this problem. If
any of you have any
suggestions, please contact us at
tim@artistic-arborist.com to share your insights. We welcome any input
into trying to find an effective treatment for this terrible "disease." |
