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Is the Emergence of Dothistroma Needle Blight of Pine in France Caused by the Cryptic Species Dothistroma pini?

First and fourth authors: INRA Nancy, UMR INRA/UHP 1136 Interactions Arbres/Microorganismes, 54280 Champenoux, France; second author: ANSES, Laboratoire de la Santé des végétaux, Domaine de Pixérécourt, BP90059, F-54220 Malzéville, France; and third author: Ministère de l'agriculture de l'alimentation et de la pêche, DGAL-SDQPV, Département de la Santé des Forêts, 252 rue de Vaugirard, 75732, cedex 15, Paris.

Dothistroma needle blight (DNB) emerged in France in the past 15 years. This disease is induced by two closely related species: Dothistroma septosporum and D. pini. Although both species are currently present in France, only D. septosporum was reported in the past. We investigated whether a recent arrival of D. pini in France could be a cause of the DNB emergence. We analyzed herbarium specimens of pine needles with DNB symptoms using polymerase chain reaction techniques to study the past frequency of D. pini in France. We also determined the present distribution within the country of D. septosporum and D. pini and compared it with the spatial pattern of DNB reported in the Département de la Santé des Forêts (DSF; French forest health monitoring agency) database. Although D. pini was detected on herbarium specimens from 1907 and 1965, it was not frequent in France in the past. Today, it is frequent, although not present throughout the country, being absent from the north and the east. There is no relationship between the D. pini distribution in France and the spatial pattern of DNB reported in the DSF database. Thus, the emergence of DNB in France cannot be explained by a recent arrival of D. pini.

Additional keywords: Mycosphaerella pini, Pinus.