Troubleshooting
Blue Douglas Fir problems — and how to fix them
Blue Douglas Fir (Pseudotsuga menziesii var. glauca) is generally forgiving once you match its basics, but a few issues come up again and again. Here is what each one looks like, why it happens, and the fix.
Douglas fir tussock moth
Caterpillar outbreaks can cause significant defoliation. Monitor for egg masses and treat with Bt in early summer if needed.
Swiss needle cast
Fungal disease causing premature needle drop, most common in coastal, wet conditions. The glauca variety is generally more resistant.
Root rot in wet soils
Prolonged waterlogging causes rapid root decline. Ensure excellent drainage.
Aphids
Woolly aphids and Douglas fir aphids can colonise foliage. Treat with horticultural oil or insecticidal soap.
Bark beetle
Stressed or weakened trees are susceptible to bark beetle attack. Maintain tree health with adequate water and avoid bark wounds.
Prevent blue douglas fir problems before they start
Most blue douglas fir issues are care-mismatch, not bad luck. Dial in the basics:
Blue Douglas Fir problems — FAQ
Why is my blue douglas fir douglas fir tussock moth?
Caterpillar outbreaks can cause significant defoliation. Monitor for egg masses and treat with Bt in early summer if needed.
Why is my blue douglas fir swiss needle cast?
Fungal disease causing premature needle drop, most common in coastal, wet conditions. The glauca variety is generally more resistant.
Why is my blue douglas fir root rot in wet soils?
Prolonged waterlogging causes rapid root decline. Ensure excellent drainage.
Why is my blue douglas fir aphids?
Woolly aphids and Douglas fir aphids can colonise foliage. Treat with horticultural oil or insecticidal soap.
Why is my blue douglas fir bark beetle?
Stressed or weakened trees are susceptible to bark beetle attack. Maintain tree health with adequate water and avoid bark wounds.