Needle Cast, Rhabdocline
Rhabdocline spp
4 host plants · Fungal
Last updated
This profile contains verified disease data from extension databases. Regional field notes and expert review are in progress.
Douglas-fir needles show yellow spots developing to deep red-brown mottled areas by spring, with orange fungal structures visible on the underside; needles drop by June. Rhabdocline fungi favor cool, moist spring conditions. Avoid low-lying sites with poor drainage, space for air flow, and avoid east-side seed sources that are highly susceptible.
Avoid planting in low-lying areas with poor air drainage. Space plants for good air circulation. Remove infected material promptly and improve growing conditions to limit pathogen spread. Good sanitation, adequate spacing, and proper irrigation practices reduce disease pressure over time.
Quick Reference
Management
Bud break through new needle elongation (spring). Preventive fungicide at bud break when new needles are emerging.
Conifer needlecast fungi infect newly emerging needles at bud break in spring; wet conditions during needle elongation are critical for spore germination (PNW Gardeners Handbook Ch 17).
Cultural Controls
- Avoid planting in low-lying areas with poor air drainage.
- Space plants for good air circulation.
- Control weeds around the bases of trees.
- Remove and destroy infected trees from Christmas tree plantations.
- Avoid using east-side and Rocky Mountain seed sources.
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