ANSES’s (FR) Plant Health Laboratory Mycology Unit has developed a PCR test to distinguish the fungus responsible for citrus black spot from that of a recently discovered related species. This test will improve the ability to detect this pathogenic fungus, thus preventing it from being introduced into Europe.

Citrus black spot disease affects most plants in the Citrus genus, especially lemons and oranges. It is caused by the parasitic fungus Phyllosticta citricarpa. While the presence of the fungus does not affect the taste of infected fruit, the black spots that appear on them make them unfit for marketing. In addition, the disease reduces the productivity of fruit trees by also affecting the leaves and by causing premature fruit drop. This disease therefore has a major economic impact.

The fungus is present on every citrus-growing continent except Europe. To prevent its introduction, the European Union has classified it as a quarantine pest: imported citrus fruit must be free of the fungus.

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