Cane Borers and Core Rot: Identification and Prevention

The Hidden Enemy Inside Canes

Hollow, soft, discolored cane centers in Zone 6 hybrid teas and floribundas indicate cane borer larvae feeding inside, followed by bacterial rot in winter. You rarely see the insect—just the damage.

Integrated Management

• Prune timing: Fall or very early spring (before borers lay eggs).
• Seal cuts: Elmer's glue or Vaseline + food coloring (to track sealed canes).
• Deadhead by snapping—avoids creating entry holes.
• Remove infested canes entirely to healthy white pith.

Other Culprits

Carpenter bees make clean holes for nesting—they're beneficial (eat pests). Don't kill them.

Borers prefer hybrid teas; tougher old garden roses and shrubs are less affected. Some varieties are especially susceptible.