Diseases

Grapevine leaf spots

Vitis L.

Grapevine leaf spots represent a symptomatic complex involving manifestations of fungal and viral infections, such as phomopsis cane and leaf spot, alternaria leaf spot, downy mildew, anthracnose, and grapevine red blotch virus.

In the reference 27 varieties crop Grapevine, where this is mentioned in the description.

Phomopsis cane and leaf spot, caused by Phomopsis viticola, manifests as small dark spots with a chlorotic halo along the veins, leading to leaf curling and tearing of the leaf blade. Alternaria leaf spot is characterized by the appearance of circular yellowing spots, which then become necrotic and develop an olive-colored mold during humid weather.

The grapevine red blotch virus (GRBV) causes leaf reddening in red-fruited varieties and chlorosis in white-fruited ones, spreading from the bottom of the vine upward. Other forms of leaf spots include the oily spots of downy mildew (Plasmopara viticola) with white mycelium and the circular spots of anthracnose (Elsinoë ampelina), often accompanied by the shedding of affected tissues and the formation of holes.

Breeding for resistance to these pathogens relies on interspecific hybrids and the use of genetic resistance loci, such as Pva and Pvr for downy mildew or Unr for powdery mildew. Identification of the specific leaf spot pathogen requires analysis of associated signs, including mycelium, shoot condition, and the timing of symptom appearance.

General information about the subject — on the page Leaf spot diseases.

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Vitis L. · Grapevine

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