Needle Cast on Colorado Blue Spruce: Fungicide Options in Ontario

Managing Rhizosphaera Needle Cast Without Banned Chemicals

One of 10 Colorado blue spruces in Ontario has needle cast. Provincial ban prohibits chlorothalonil (Daconil/Bravo). Local nursery recommended Bordo Copper Spray.

Cultural Control (Essential)

• Rake and destroy (bag/landfill) all fallen needles—they harbor spores.
• Improve air circulation: prune lower limbs, avoid overhead irrigation.

Fungicide Options

• Bordeaux mixture 8-8-100 (8 lb hydrated lime + 8 lb copper sulfate / 100 gal water) – classic, effective.
• Bordo Copper Spray (tribasic copper sulfate 53%) – same chemistry, ready-to-use. Approved and effective.
• Apply when new needles are half-grown and again at full elongation.
• Two years of treatment usually restores moderate cases; severe cases need 3+ years.

Why Copper Works

Copper is a protectant fungicide—it prevents spore germination on needle surfaces. Timing is critical: must be on needles before infection periods (wet spring weather).

Bottom Line

Bordo Copper Spray is an excellent, legal alternative. Combine with sanitation for best results.