Black Bark on Ornamental Pear: Possible Fungal Canker

The progression you describe—leaf shriveling, bark turning black and separating, now appearing on a second tree—strongly suggests a fungal canker disease, possibly Botryosphaeria canker or Phytophthora collar rot. Both affect stressed Prunus (plum) and Pyrus (pear) species.

Key Symptoms to Check

• Sunken, darkened areas on bark with cracked or peeling margins.
• Amber gumming or ooze at canker edges.
• Wood beneath bark is brown/black instead of healthy green/white.
• Dieback starting at branch tips and moving inward.

Immediate Steps

1. Confirm diagnosis: Take clear photos of trunk/bark symptoms and bring a sample (live wood with transition zone) to your local UC Cooperative Extension office or a certified arborist. Tehachapi's climate (hot summers, cold winters) stresses these trees.
2. Prune out dead/dying branches 6–12 inches below visible cankers. Sterilize tools between cuts (10% bleach or 70% alcohol).
3. Improve drainage if soil stays wet—pear roots suffocate in poorly drained soil, inviting Phytophthora.
4. Avoid wounding trunk/roots with mowers/string trimmers.

Treatment Outlook

Fungicides (e.g., phosphonates for Phytophthora) may slow spread if caught early, but cannot cure established cankers. The priority is reducing stress: deep, infrequent watering; mulch ring (not against trunk); appropriate fertilization.

Get a professional on-site diagnosis—this is too advanced for guesswork.