Poinsettia (Euphorbia pulcherrima)-Bacterial Stem Rot

Latest revision: 
March 2024

Cause Pectobacterium carotovorum and Dickeya chrysanthemi, bacteria that can spread by workers' hands, cutting tools, or contaminated water supplies. It also can survive in plant debris. Wounds are a common entry way for the bacteria. Any factor that stresses cuttings favors the disease such as long shipping times. Cool temperatures may delay symptoms until warm weather occurs. A few infected cuttings can increase the disease by 6% to 21% when dipped into solutions prior to sticking.

Symptoms Cuttings develop a soft, mushy rot beginning at the basal end. Symptoms can develop in 24 to 48 hours when conditions are optimal for disease development. If infected plants survive the cutting phase, stunting and vascular browning may occur later. Stems and leaves also may wilt, darken, and look water-soaked, followed by complete plant collapse.

Cultural control The focus is on keeping aboveground plant parts dry.

  • Destroy plant debris in and around the greenhouse.
  • Avoid waterlogging the rooting medium. Water at the base of plants. Use a medium that holds less water overall.
  • When propagating keep misting minimal, especially at night, and stop as soon as possible once cuttings begin to root.
  • Keep temperatures below 90°F.
  • Wash hands before pinching, and keep cutting tools disinfected.
  • Give stock plants moderate nitrogen fertility. Avoid calcium deficiency.
  • Disinfect cutting knives, containers, and benches frequently when harvesting cuttings. Use two knives so a worker can cut with one while the other soaks. When done with a batch, cultivar, etc. switch one knife for the other and allow the used one to soak.
  • Use clean disposable containers for dipping solutions and use a new container every time it needs to be refilled.

Chemical control Focus on cultural controls. May be very helpful for stock plant treatment prior to taking cuttings.

  • FireWall 50 WP at 1.36 oz/25 gal water. Group 25 fungicide. 12-hr reentry.
  • Phyton 27 at 1.5 to 3.5 oz/10 gal water. Group M1 fungicide. 48-hr reentry.

Reference Buitenhuis, R., Poleatewich, A. M., Jandricici, M., and Brownbridge, M. 2020. Risk of spreading soft rot through cutting dips against whiteflies in greenhouse-grown poinsettia. Plant Disease 104:2262-2268.