A new chestnut yellows observed in Italy
In Italy in summer 1996, an unusual vegetative disorder was observed on 2 contiguous chestnut trees (Castanea sativa) growing on the slopes of the Apennino Tosco-Emiliano (orchard of Monte Romano, Brisighella, Province of Ravenna, Emilia-Romagna). Affected trees showed leaf interveinal chlorosis. On one tree, half of the canopy was affected, showing a striking yellow colour. Leaves also showed brownish desiccated margins, generally curling down. Twigs were shortened, leading to some cases to formation of rosettes (but no witches' broom). Fruiting was severely impaired. Other trees showing symptoms were later seen (1996-97) in the same orchard of Monte Romano (20 trees affected and some were dying), and also a few kilometres away, on the same slopes of the Apennino (Marradi and Borgo San Lorenzo, Province of Firenze, Toscana). Surprisingly, similar symptoms were seen 300 km away in the region of Trentino-Alto Adige, along the national road 349 connecting Trento to the plateau of Lavarone, near the locality of Centa San Niccolò, and the plateau of Tesino near the village of Pieve Tesino. Preliminary attempts to detect phytoplasmas in diseased trees
failed. Considering the severe effects on the fruiting and survival of chestnut trees, the authors stressed that further studies will be carried out to clarify the etiology of this disorder and to determine its extent in Italy.