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Boeremia exigua

(Desm.) Aveskamp, Gruyter & Verkley  var. exigua (2010)



- Classification : Fungi, Ascomycota, Dothideomycetes, Pleosporomycetidae, Pleosporales, Incertae sedis
- Synonyms : Ascochyta nicotianae, Didymella sp. (teleomorph)
- English names : Ragged leaf spot, Phoma leaf blight

- Frequency and severity of disease incidence 

 The fungus Boeremia exigua var. exigua is widely distributed around the world but is not considered as an important pathogen of tobacco. To our knowledge this fungus has not been reported in France.

- Symptoms

This leaf fungus causes irregular to circular, brown to ashy grey leaf spots (figures 1 to 5). Occasionally, the spots are very large. Numerous pycnidia containing two-septate spores (see photos) can be found scattered on these spots. Eventually the centre of the spot, which is dead tissue, disintegrates leaving a ragged appearing leaf. The spots can be observed on young seedlings and mature leaves of large plants.

- Biology

The pathogen may be active in both in cool and warm conditions. Its optimum temperature for growth is from 20 to 24°C. Likely it survives on plant debris. The fungus spore (conidia) are produced in pycnidia (figure 6). These conidia ensure the survival and dissemination of the pathogen.

- Protection Methods

No product is registered for control of this disease in France.

Last change : 02/13/18
  • Author :
  • D Blancard (INRA)
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