Researchers at Neiker-Tecnalia, the Basque Institute for Agricultural Research and Development, have confirmed the significance of eutypa dieback disease in vineyards in the Rioja Alavesa wine-growing area. It is a fungal disease –caused by fungi– which is relatively difficult to spot as the symptoms that are displayed in the wood are identical with those of other more widespread diseases, like botryosphaeria canker (bot canker or black dead arm). The specialists have confirmed the presence of eutypa dieback disease when locating the sexual form of the Eutypa lata fungus, responsible for the disease, in wood samples gathered in several vineyards in the area. This sexual form is indispensable for the cycle of the disease to be completed, and it is the first time that it has been described in the Rioja Alavesa area. The research has been led by the biologist Argiñe Muruamendiaraz, who has submitted a PhD thesis on the subject.
The great similarity displayed by the various fungal grapevine wood diseases makes it difficult to determine which specific disease is affecting the plants. In the case of the Rioja Alavesa area, there was an argument between vine growers and agricultural experts as to whether eutypa dieback disease was present in that area. So back in the 1980s Enrique López and Javier Mateo, of the Casa del Vino (wine research centre) in Laguardia, described its characteristic symptoms. Nevertheless, over the years that followed, work in the Castilla-Leon region and Catalonia came across more instances of botryosphaeria –another family of fungi– in "V" shaped wood necrosis. The Neiker-Tecnalia research resolved this argument when they proved that there was a significant presence of the Eutypa lata fungus. This could be linked to the increased coolness in the climate of the Sonsierra area. Eutypa dieback disease affects the trunks and branches of the stocks and reduces grape yield and quality. But its most negative effect is that it kills the plant within the space of 30 years; this is extremely bad news for vine growers, because it is in fact the old stock which is the most highly valued as far as the production of quality wine is concerned.
To confirm the presence of Eutypa lata, the team of experts placed traps in various spots in the Rioja Alavesa area in order to capture the spores infesting the air. The presence of Eutypa lata spores was established, but conidia (asexual spores) of Diplodia seriata (belonging to the botryosphaeria family) were found to be more widespread.
To check the relative responsibility of the two fungi, the Neiker-Tecnalia researchers carried out a study to confirm whether both of them were capable of inducing the disease. Various vines inside a greenhouse were inoculated with Eutypa lata and Diplodia seriata. All the plants displayed wood problems, but only the ones inoculated with Eutypa lata developed symptoms consistent with eutypa dieback in their leaves, like frail bud burst and leaf edge necrosis, which can be spotted so much in the vineyards of the Rioja Alavesa area. Diplodia seriata, however, only caused canker in the vine shoots.