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Symptoms
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Redbrown discoloration restricted to the distal half of the needle, initially roundish redbrown spots. Later, the discolored part of the needle turns pale, then grey and finally drops. Then the remaining basal part also turns yellow and is shed. In the reddish areas fruiting structures of the microfungus Sydowia polyspora ("Kabatina abietis") develop, which show a distinct black surface. The phenomenon can be mistaken for herbicide-damage or other contaminations by chemicals, where secondary microfungi produce similar symptoms, but also for frost damage or attacks by gall midges. A definite diagnosis can be achieved only by a lab.
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Impact
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Kabatina-needle disease (=CSNN, Current Season Needle Necrosis) has been known from its symptoms from the Eighthies on, but it was described and named as a new species in 1993. Later studies showed, that the fungus is identical with Sydowia polyspora (asexual stages Sclerophoma pithyophila and Hormonema dematioides). This species is nearly ubiquitous and contributes to the decomposition of needles and twigs of many conifers. Moreover it is an endophyte (present in living tissues without causing symptoms). The reasons, why it produces the characteristic symptoms in needles of some conifers are not fully understood. Confirmed associations are to intensive sunlight during the elongation period of the young shoots in spring. The symptoms are laking in shaded needles. The disease mainly occurs on Abies grandis and A.nordmanniana and during the past years it has become an increasing problem in Christmas tree production. The disease has never been endangering the life of trees, although heavy loss of needles is quite common.
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Control
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there are no curative measures availble: application of fungicides is mostly ineffective. On endangered sites (high humidity, high radiation in spring, slopes) the susceptible fir species should be (if possible) shaded (f.i. by admixture with other tree species).
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| Hosts |
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Fir;
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| Affected plant parts
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Needle;
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