This fungus can cause large harvest losses in grape vines.
Phomopsis [Phomopsis viticola]
During June, numerous black spots appear on the young leaves. Sickened leaves yellow and die prematurely. Affected grapes turn dark-blue and dry up (Picture 1). In fall, the bark of the maturing wood gradually turns a white-gray color. The fruiting bodies of the fungus are clearly visible against the background of the bark (Picture 2). With severe infection, the fungus damages the buds; they bud only weakly or not at all. Rotted areas appear that lead to stunting and may lead to the death of entire vines.
The primary infection occurs immediately after budding. Temperatures of +1 °C and a relative humidity of 86% are sufficient for infection to occur. In spring, masses of mature spores explode from the fruiting bodies.
Preventative control should be performed to protect the green vine parts from primary infections. The first fungicide application must be made as soon as the plants bud. Further fungicide treatments must be performed afterwards.