Black rot started appearing in 2002 throughout all of Germany in large wine-growing regions and presents a significant problem. During mild and humid weather black rot spreads and can lead to harvest losses of between 5 to 80%.
Black rot [Guignardia bidwellii]
Black rot infects grape vines.
Pattern of damage
The fungus Guignardia bidwellii causes damage that affects the leaves, shoots and fruit. Approx. 1 cm large, round brown spots develop on the leaves that are clearly delineated from the healthy tissue by a dark-brown margin (Picture 1). In advanced stages, black fruiting bodies (pycnidia) are seen, which are circularly arranged. The shoots have longish, black discolorations on which pycnidia develop as well. The fruit progresses through several stages. Initially, light-gray discolorations are seen which turn light-brown over time and spread over the fruit (Picture 2). Then these spots become continuously darker and pycnidia form on the fruit as well. In the final stage, the fruit is dry, exhibiting a dark-blue to almost black color, and is covered in pycnidia. They turn into so-called fruit-mummies.