(en anglais seulement)
Needle dieback, which primarily affects container-grown Douglas-fir seedlings, is not fully understood. Similar symptoms have occurred to a lesser extent on true fir, spruce, and western larch. Symptoms (Figure 58), which first appear when seedlings are 1-2 cm in height, include stunted root and shoot growth, needle chlorosis, twisting and wilting of shoot tips, and needle tip dieback. Distribution of affected seedlings within seedlots is patchy, but often the disease is more prevalent in individual batches of growing medium. Plants affected during germination and early growth stages rarely reach end-of-season growth standards. Seedlings affected later suffer some needle damage but few other effects.
Studies indicate that a complex of Pythium species in association with unfavorable cultural practices, such as high growing medium temperatures and imbalanced ammonium-to-nitrate ratios, may be associated with needle dieback. To date, little information is available on dieback management, but apparently growing medium sterilization reduces dieback incidence.
Husted, L. and S. Barnes. 1988. Dieback of container-grown Douglas-fir seedlings. Canada-British Columbia Forest Resource Development Agreement draft report prepared for CIP Inc. 31 p.
|
Other Fungi |
Insects |
Environmental |
|---|---|---|
|
|
Drought |
|
Principal, locally grown hosts |
Host age and season when damage appears |
|
Nursery type and location |
|
|
|
|---|---|---|---|---|---|---|
|
Bareroot |
Container |
|||||
|
Age |
Season |
Coastal |
Interior |
Coastal |
Interior |
|
|
Most severe on Douglas-fir, possibly on true fir; spruce and western larch |
1+0 |
Early spring through early summer |
No |
No |
Yes |
Yes |
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Figure 58. Needle dieback of Douglas-fir.