{"id":9555,"date":"2013-06-05T10:38:27","date_gmt":"2013-06-05T14:38:27","guid":{"rendered":"http:\/\/extension.umaine.edu\/ipm\/?page_id=9555"},"modified":"2021-08-31T15:47:32","modified_gmt":"2021-08-31T19:47:32","slug":"5106e","status":"publish","type":"page","link":"https:\/\/extension.umaine.edu\/ipm\/ipddl\/publications\/5106e\/","title":{"rendered":"Black Rot of Grape"},"content":{"rendered":"

\n \n \"Print\n <\/a>\n <\/div><\/h3>\n

Pest Management Fact Sheet #5106<\/h3>\n

Bruce A. Watt, Extension Plant Pathologist<\/em><\/p>\n

For information about UMaine Extension programs and resources, visit extension.umaine.edu<\/a>.
\n<\/strong>Find more of our publications and books at extension.umaine.edu\/publications\/<\/a>.<\/strong><\/p>\n

Introduction<\/h3>\n

The fungus Guignardia bidwellii<\/i> causes black rot of grape. It is the most common and serious disease of grape in Maine and during years when the weather is favorable losses can range up to 80% of the crop.<\/p>\n

Symptoms<\/h3>\n

The fungus infects newly emerging leaves, fruit, canes, shoots, and tendrils. Infections are usually first noticed on the leaves where they appear as small spots which may enlarge to 1\/4 inch in diameter. The spots are commonly light tan in the center and may be circled by a dark tan band (Fig.1). As the infection ages, two types of tiny, dark, spore-producing structures form within the spots (Fig.2). These superficially similar structures (Fig.3) are either spermagonia (Fig.4) or pycnidia (Fig.5) and produce spermatia (Fig.6) and conidia (Fig.7) respectively. Spots formed by infection of the shoots are larger and darker and will also produce spores.<\/p>\n\n\t\t