Fat Albert Blue Spruce Decline: Spider Mites and Proper Fertilization

Diagnosing Browning in Fat Albert Spruces

When two of four Fat Albert blue spruces show recurring browning—especially on lower and interior needles while tops remain green—spruce spider mites are the prime suspect. Here's how to confirm and treat.

Spruce Spider Mite Damage

• Mites are tiny arachnids (not insects) that pierce needles and suck sap.
• Feeding causes stippling (tiny yellow spots), followed by browning and needle drop, usually starting on lower, inner branches.
• Populations peak in spring and fall; they go dormant in summer heat.
• Damage often appears months after feeding occurred.

How to Check for Mites

1. Hold a white sheet of paper under a symptomatic branch.
2. Tap the branch sharply.
3. Look for tiny, slow-moving specks crawling on the paper.
4. If you see dozens per tap, treatment is warranted.
5. Repeat checks every 7–10 days during spring and fall.

Treatment Options

• Insecticidal soap: Thoroughly coat foliage; repeat as needed. Low toxicity.
• Acephate + fenbutatin oxide (e.g., Ortho Systemic Insect Killer): Systemic action; follow label carefully.
• Apply in early spring or fall when mites are active. Summer applications are less effective.

Fertilization: Test First, Then Decide

The lawn service's suggestion of high-phosphorus fertilizer is not recommended without a soil test. Most soils already have adequate phosphorus. Excess phosphorus can harm mycorrhizal fungi and pollute waterways.

• Best practice: Get a reliable soil test (through your county extension).
• If fertilizing: Use a balanced fertilizer (e.g., 13-13-13) at 1 lb per inch of trunk diameter in early April—before July 15 at latest.
• Late-season fertilization stimulates tender growth that won't harden before winter.

Other Considerations

• Ensure no "weed and feed" products were used nearby—herbicides can damage tree roots.
• Check soil drainage; spruces hate wet feet.
• If mites are controlled, the trees should look much better by next spring.