Arborvitae Brown Patches: Abiotic or Fungal Twig Blight

4 new arborvitae (6 ft), 2 have isolated medium-brown 5 sq in patches on branches. Trimmed out. What else?

Possibilities

• Abiotic: Water extremes, sun, transplant shock
• Biotic: Kabatina/Phomopsis/Pestalotiopsis twig blights

Blight Details

• Kabatina: 1-yr tips brown/ash-gray, black pimples on dead/live junction
• Phomopsis: Similar, different spores
• Pestalotiopsis: Tan/brown tips, black pimples

Management

• Prune/destroy infected
• Mancozeb (Kabatina), azoxystrobin/thiophanate-methyl/copper (Phomopsis), copper (Pestalotiopsis)
• Protect from winter injury, drought