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Leaf spot on celery

Cercospora apii

Profile

The leaf spot fungus Cercospora apii occurs on celery during prolonged periods of higher temperatures during the summer months. Brown spots appear on the leaves of infested plants, which eventually dry out.

Damage symptoms

The first symptoms are the appearance of small, roundish, yellowish to light brown spots on the leaves, which rapidly increase in size. The spots dry out and turn an intense brown. If the leaf spots flow together, the leaves wilt and eventually wither. On the surface, symptoms may be initially confused with those of Septoria leaf spot disease. Cercospora apii usually appears earlier than Septoria apiicola.

Host plants

In addition to celery(Apium graveolens), other host plants include wild carrot (Daucus carota) and parsnip(Pastinaca sativa).

Distribution

The fungus is common in celery-producing countries worldwide.

Propagation and transmission

Cercospora apii is seed-borne and can persist on infected plant debris incorporated into the soil. Spores are spread by wind, water droplets, field operations, and machinery.

Temperatures between 15 and 30 °C promote the occurrence of Cercospora apii, but the fungus spreads preferentially at temperatures between 22 and 28 °C.

Economic importance

Cercospora apii occasionally occurs on celery, but due to its higher temperature requirements (over longer periods) it has so far only gained economic importance in Austria in warm summers.

Prevention and control

  • Use of pest-free seed
  • Adherence to a crop rotation of at least four years
  • Deep plowing of crop residues
  • Controlled irrigation

If this fungus becomes more important on celery due to changed weather conditions(Cercospora apii prefers higher humidity and temperatures between 15 and 30 °C), the area of spread, the demands of the pathogen, the infestation intensity and frequency as well as possible modified countermeasures must be surveyed.

Last updated: 17.11.2021

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