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Managing current season needle necrosis in Christmas trees

| April 24, 2013
Close up on Fir tree with necrosis

Marked necrosis with heavy needle drop already apparent. Picture courtesy Lars Bo Pedersen.

Uptake and utilization of nutrients is the cornerstone of physiological health in green plants, but deficiencies in specific nutrients have long been known to play a crucial role in the development of disease caused by plant pathogens. Calcium, a poorly mobile nutrient with an important strengthening role in the structure of plant tissue is well established in this respect.

CSNN (Current Season Needle Necrosis) continues to cause serious losses for Christmas trees in North America, mainly Noble fir (Abies procera) and Grand fir (Abies grandis) and in Europe the Nordmann Fir (Abies nordmanniana), with the United Kingdom the latest country to be hit. CSNN is proving to be one of the most intractable and difficult to decipher problems affecting the Christmas tree industry both sides of the Atlantic Ocean.

CSNN as the name suggests, only affects current season’s needle (leaf) growth, starting to show in spring and through into summer. Needles affected by CSNN develop brown to tan bands shortly after the shoots elongate in spring. Affected areas subsequently turn reddish brown and spread over and across the whole fir needle. Badly affected needles are shed but those with just banding symptoms stay attached to the branches.

The fungus Sydowia polyspora has been isolated and identified from needles with CSNN sourced from a number of Abies spp (true firs) including noble and grand fir from the Pacific North West. Inoculation trials were conducted on small seedlings but the results were variable leading some scientists to suggest that the fungus may just be an endophyte and not the primary cause of CSNN.

Early research findings in Denmark suggest CSNN is due to the inability of trees to access sufficient calcium, leading to a loss of leaf tissue integrity and enabling infection by Sydowia polyspora with consequent disease development.

This is a preview of a full article published in International Pest Control – March/April 2013 issue.

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Author: Dr Terry Mabbett*
*Director, Dr Terry Mabbett Consultants


Category: Forestry-Plantation

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