The
Christmas Tree:
RELATED SITES
While noble and Fraser fir, are highly susceptible to Phytophthora root rot, there is considerable variation in the susceptibility Abies spp. to this disease. One potential option to minimize the impact of this disease in sites that are conducive to its development is to plant a species like Nordmann, Turkish or Momi fir that are less susceptible than noble or Fraser fir. Studies would have to be conducted to determine if these species have suitable horticultural characteristics for use as Christmas trees and determine if they have the excellent needle and moisture retention characteristics that are needed in today’s market. Growers might also use less susceptible species as a rootstock for species such as noble and Fraser fir so they could grow these species in sites that are conducive to Phytophthora root rot (Tompkins 1989).
Current
season needle necrosis
In addition to Phytophthora root
rot and stem canker, there are two additional diseases that limit the
production of high quality noble fir Christmas trees in the PNW. Current
season needle necrosis (CSNN) is a poorly understood physiological
disorder that occurs on noble and grand fir Christmas trees grown
throughout production areas in western Oregon, Washington, and British
Columbia (Chastagner et al 1990c and Chastagner 1997). CSNN also occurs on
noble fir in Ireland and Denmark. In Denmark, the condition is also
referred to as "røde nåle på nobilis" (red needles on noble
fir).
| In the PNW, initial symptoms of CSNN appear on current season needles during early June. Symptoms consist of tan discolored bands. In some cases, the area of discoloration expands and involves the distal portion of needles or the entire needle. Damaged portions of needles turn reddish-brown in color by mid summer. The incidence of symptomatic needles increases rapidly during June and July. |
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| Unlike grand fir, where symptomatic needles are distributed throughout the tree, branches in the upper portion of noble fir trees can have twice as many symptomatic needles compared to branches in the middle and bottom portion of trees. CSNN damage is strongly related to site, being more severe at low elevations, which are typical of many Christmas tree plantings in the PNW. There is also considerable variation in disease development on trees in different areas within a given site. Growers' observations indicate that CSNN is less of a problem at higher elevation sites and in natural stands. Growers have also associated initial symptom development with high temperatures and observed that certain trees tend to show symptoms year after year. |
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1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | References © Copyright 1999 by the American Phytopathological Society. All rights reserved. |
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