My Grapevine Has Brown Leaves

Downy Mildew

• The fungus Plasmopara viticola causes downy mildew. This disease first appears on the leaves as small, yellow lesions. As the lesions grow, they cause the entire leaf to turn brown and wither. The undersides of the leaves may have a white or gray growth. Cane tips may become blighted or twisted on some varieties. Treat downy mildew with a fungicide.

Phomopsis Leaf and Cane Spot

• Caused by the fungus Phomopsis viticola, Phomopsis leaf and cane spot disease appears during rainy, cool weather. The disease initially causes small angular dead spots in young leaves. As the disease progresses, stems, tendrils and leaf petioles develop brown or purple lesions. Treat this disease with a fungicide.

Black Rot

• Black rot is caused by the fungus Guignardia bidwellii and is common throughout the eastern U.S. and Canada. The disease causes brown or black lesions to form on the leaves. The lesions are 1/8 to 1/4 inch in diameter and may have black margins and black pimples. Developing fruit shrivels, hardens and drops from the vine. Spray infected grape vines with a fungicide to control black rot.

Considerations

• Grapevine diseases are more common in vineyard settings than in home gardens. To prevent most diseases, plant grapevines in a sunny, open area with good air circulation between the plants. Train and prune the plants annually to control their growth. Remove dead fruit, leaves and stems from the ground promptly because diseases overwinter in these materials.