Douglasienschäden

Damaged afforestation of Douglas firs

Kronenbild 2

Reddening and cast of older needles

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Phaeocryptopus gaeumannii - needle cast

At the moment, serious needle loss and discolouring is noticed in Douglas fir plantations in Eastern Austria. Especially affected are 10 to 20 year old stands which were thinned and pruned last winter in the Wein and Waldviertel.

Symptoms

Two different damage symptoms may appear at the same time and even at the same site.
In March/April 2003 infested trees showed a sudden yellowing of the needles and a needle loss in the whole crown area which has been more pronounced towards the stem than in the area of younger foliage.
The discoloured needles are often infested by Phaeocryptopus - needle cast. Studies on cambium and phloem tissue reveal the dieback of the affected twigs and branch parts. This symptom is visible more often on the hilltop or on slopes directed towards the South than on other sites.
Another possible symptom is a pronounced red discolouring on the treetop of the Douglas firs. Lower twigs and stem parts show no or only few signs of damage. This can be observed especially on lower slope sites and north east to south west exposed locations. No relationship to Phaeocryptopus - needle cast was found.

Cause(s)

The damages are probably due to frost drought or frost drought together with late frost and winter frost. Thinning and pruning may have had some influence due to increased solar radiation of the tree crowns. Some sample investigations have shown that part of the damages dates back to the winter 2001/2002 (clearly reduced shoot lengths).

Impact on Douglas firs

Single trees but also entire stands show needle loss of more than 80 %. Neither regeneration nor recovery of the affected stands can be expected. The same applies to trees where the cambium is largely discoloured or partly dead. For those trees with less needle loss or where only smaller parts of the crown are concerned, there is still hope that the tree may recover although some secondary damages may be expected due to Phomopsis-disease of Douglas fir, as well as bark beetles and Armillaria.

Control measures

Heavily infested trees should be removed from the stand. When entire stands are infested, early clear-cutting and conversion of stands into other tree species is recommended. As bark beetles have already been detected on the attacked trees it is recommended to act with caution in order not to lose the adjacent conifer stands or the already damaged Douglas fir.

Damages to Douglas firs
Tomiczek Ch., Cech Th.	German
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