Grapevine decline syndrome associated with Botryosphaeria spp.: a risk for Umbrian vineyards?

Surveys in four Umbrian vineyards suffering for decline syndrome were carried out between 1995 and 2003. Field symptoms varied from mild chlorosis, leaf and fruit wilting, cankers on canes, sometimes in association with brown wood streaking of branches. Diseased vines showed a gradual decline in vigour and yield. In 1995, decline syndrome was observed on 1% of the plants localized in one row whereas in 1999, a vineyard (3000 m2) of white wine cv Trebbiano Toscano was seriously damaged (100%). In 2002 and 2003, in two vineyards, disease incidence ranged from 60 to 70%. Isolations were made from cankers onto potato-dextrose agar (PDA) plates. Dark grey colonies with dense aerial mycelium developed and produced black pycnidia within a month, under near-UV light. The isolates were identified as the anamorph of Botryosphaeria spp. on the basis of conidial shape (length/width ratio), cultural and morphological characters. Pathogenicity tests were performed in 1999 by inoculating ten 1-year-old rooted grape Trebbiano Toscano cuttings. Mycelium plugs were placed on wounds drilled into canes and covered with parafilm whereas control vines were inoculated with sterile PDA. Artificial inoculations, using the same technique and three isolates, were carried out in 2003 on red wine cv Cabernet Sauvignon rooted cuttings. No symptoms developed on the inoculated vines. In 1995 and 1999 three spray applications of thiophanate-metyl and the removal of pruning debris resulted to be good sanitation practices as no disease symptoms were observed on vines in the following years. Further studies and surveys are in progress.