Diagnosing Viburnum Hedge Decline: Check for Scale, Leaf Spot, and Borers

Systematic Inspection

A 20-ft viburnum hedge dropping yellow-spotted leaves with dead branches underneath needs a methodical check:
1. Leaf undersides: White fuzzy masses = scale insects.
2. Branches: White cottony spots on bark = scale.
3. Live leaves: Black/brown spots = fungal leaf spot.
4. Base of stems: Exit holes = borers.

Why Fertilizer Alone Failed

Feeding stressed plants without addressing the primary pest/disease worsens the problem. The previous "tree specialist" may not have been an ISA-certified arborist.

Next Steps

Identify the specific issue, then treat accordingly: horticultural oil for scale, fungicide for leaf spot, systemic insecticide for borers. Only then fertilize to support recovery.