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Xanthomonas fragariae

EPPO code

XANTFR

Common names

English names: Angular leaf spot
Nordic names: Jordbærbladpletbakteriose (DK), Maniskan lehtibakterioosi (FI)

Major host plants

The natural host range is limited to the genus Fragaria.

Symptoms

Symptoms develop on the leaves:

  • Tiny angular spots are first evident on the lower leaf surface.
  • Spots look wet and translucent when held up against light.
  • Spots enlarge into angular shaped limited by veins. Lesions join together and become visible on the upper leaf surface as irregular reddish-brown spots.
  • Spots have a shiny appearance with bacteria ooze in humid weather. When the ooze dries up, it leaves flaky residue.
  • Dead leaf tissue breaks off and gives diseased leaves a ragged appearance.

The symptoms can be confused with leaf spot fungi.

Courtesy of EPPO - U. Mazzucchi - Università di Bologna (IT)

See more pictures on EPPO´s website

Distribution

Xanthomonas fragariae was first described in North America. It probably spread from there with planting material to other continents.

A map can be downloaded from EPPO’s website. See instructions here.

Biology

The disease is introduced to new fields with infected planting material. Disease development is favoured by moderate to cool daytime temperatures (below 20°C), low night temperatures, and high relative humidity (long periods of precipitation and irrigation). Bacteria that exude from lesions under high-moisture conditions provide inoculum that can be rapidly spread to healthy plants by splashing water. The bacterium is very resistant to desiccation and may survive for extended periods in dry leaves or frozen plant material. It does not survive free in the soil. Symptoms develop within 5-6 days at 20-25°C, 14 days at 10°C. No symptoms are observed on infected plants at 5°C, but the disease will develop when the temperature increases.

Major pathway(s)

The dispersal of the pathogen over long distances can be due to infected planting material, which may or may not show symptoms.

Detection and inspection

Plants severely infected with X. fragariae can be detected in the field by visual inspection although symptoms may resemble those of other common strawberry diseases. Symptoms are best observed during cool and wet conditions in the spring.

Detection is difficult on symptomless runners and plants from cold storage and should therefore be tested in a laboratory.

Pest status and importance

Angular leaf spot is an important disease on strawberry production worldwide. The disease has been a major economic concern for nurseries, especially those involved in international trade.

Source of information

See further information here:

Author: Christiane Scheel and Elise T. Yamamoto Buch
Editor: Dorthe Vestergaard

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