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Gummy stem blight or black stem rot is an important disease in cucumber and other curcubits. It is caused by the fungus Stagonosporopsis cucurbitacearum (syn. Didymella bryoniae).

What damage can cause Didymella?

  • The pathogen attacks stems and leaves. If the infection is severe, it can even kill the plants
  • It also infects flowers and developing fruits, causing fruit end rot. Sometimes this symptom only appears after harvest.

What are the characteristics of Didymella?

  • Asexual spores (conidia) and sexual spores (ascospores) are produced in small black round structures called picnidia and perithecia, respectively, and can be found on the same lesion.
  • The conidia are sticky spores and can be dispersed by water splash or on hands and tools during routine crop work
  • The ascospores are released into the air and are very important for the long-distance dispersal
  • The stem base of cucumber plant is often left in the substrate when a new cycle is grown in the same substrate. This tissue can be a source of ascospores and poses a risk to the new crop.
  • The fungus survives as dormant mycelium or as chlamydospores (resting spores)

How to protect plants against Didymella?

  • Destroy all organic debris from previous infected crops when possible
  • Keep plants dry
  • Avoid guttation of the plants by slowly heating the glasshouse in the morning
  • For biological control, you can rely on Prestop* and Asperello T34 Biocontrol**

*Belgium and The Netherlands
**Only in the Netherlands

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