Esca (Black Measles) and Brown Wood-Streaking: Two Old and Elusive Diseases of Grapevines

TLDR: This paper refers mostly to conditions in the Mediterranean area and focuses on the progress achieved in the understanding of esca over the last few years, as well as the relations between esca and related syndromes or diseases.

Abstract: “Esca” disease of grapevine has long been known wherever grapes are grown. The disease may be as old as vine cultivation itself. References to esca-like symptoms are found in several ancient Greek and Latin works. Greater descriptive accuracy is found in medieval works such as the Kitab al-Felahah by Ibn al-Awam, a Spanish Muslim who lived in Seville at the end of the twelfth century, and the Opus Ruralium Commodorum by Pietro de’ Crescenzi, born around 1233 in Bologna. Esca is a Latin word meaning food, aliment, or, figuratively, bait. The name indirectly refers to the fruiting bodies of certain wood-rotting fungi. For example, Fomes, which in Latin means “tinder,” is the name of a genus of basidiomycetes once used to make a dry, easily ignited material suitable to start fires when using flints. Wood decayed by these fungi, including rotted grapevine wood, burned slowly and was used to keep fires aglow without a flame. Esca is a complex disease that comprises an array of symptoms, some of which have locally given their own names to the disease. For example in California, the dark, tiny spotting of the grapes is called “black measles.” In many grapevine-growing areas of the world, the sudden wilting of esca-affected vines in summer has earned this form of the disease the name “apoplexy.” Research on the etiology of esca, which started at the end of the nineteenth century in France, can be divided into three periods. The first period began in 1898 with Ravaz (61) and ended in 1926 with Viala (79). The overall conclusion of this period was that two basidiomycetous fungi, Stereum hirsutum (Willd.) Pers. and Phellinus (Fomes) igniarius (L.:Fr.) Quél., were the causal agents, although this could not be shown by pathogenicity tests. However, in Italy in 1912, Petri (58) successfully reproduced some early internal esca symptoms with two undetermined species of Cephalosporium and one of Acremonium that had also been associated with the disease. The second period in esca research started in California in 1957 with Hewitt (35) and lasted until 1959, when Chiarappa (9) detected the relationship between internal wood decay and black measles. He also showed how a Cephalosporium sp. reproduced in vivo some of the symptoms observed in the wood of diseased vines, and how P. igniarius caused wood decay in vitro. The third period, initiated by Larignon and Dubos in 1987 (39) and still underway, is directed at understanding the role of the mitosporic (asexually reproducing) fungi that act alone or together with the basidiomycetes to cause esca and related diseases. In the 1990s, studies on esca and its etiology have intensified. This came after a dramatic upsurge in the disease, especially in Germany, Italy, and Greece, where the arsenites, traditionally used to keep esca under control, have been banned and were replaced by less effective fungicides. However, even in France, Portugal, and Spain, where restricted use of sodium arsenite is still permitted, esca is widespread in all vine-growing regions. This paper refers mostly to conditions in the Mediterranean area and focuses on the progress achieved in our understanding of esca over the last few years. Reference is also made to a decline of young grapevines caused by some of the same mitosporic fungi as those commonly associated with esca in adult vines. Finally, the relations between esca and related syndromes or diseases are also discussed.