Plant Disease Management Handbook

Cause Unknown. A leaf discoloration known as blackleaf, brownleaf, chocolate leaf, or blattbraune is a problem in eastern Washington. Blackleaf is associated with potassium deficiency, severe overcropping, poor soils, sun exposure, drought, and/or high summer temperatures. Whether these factors are directly responsible for blackleaf or merely correlative with symptom expression is unknown. Blackleaf is particularly noticeable in Vitis labrusca cultivars such as Concord.

Image related to Grape (Vitis spp.)-Blackleaf

Note the darkened areas between the leaf veins.

Photo by Russel Smithyman

See:

Grape (Vitis spp.) - Esca, Young Esca, and Petri Disease

Image related to Grape (Vitis spp.)-Black Foot Disease

Viewing trunks in cross-section, dark brown to black streaking is evident in the vascular elements due to plugging of individual or aggregates of xylem vessels with amber to black gum (gummosis) and formation of tyloses.

OSU Plant Clinic Image, 2013.

Cause Armillaria mellea, a fungus, infects vine roots, killing the cambium and decaying the underlying xylem. This is a soilborne fungus that is capable of attacking many different plant hosts. These fungi are most commonly found in forests and natural areas where they infect a variety of trees and shrubs. Therefore, the disease is most common in newly established fields that are planted on land recently cleared of native vegetation.

Image related to Grape (Vitis spp.)-Armillaria Root Rot

Mycelial fan exposed by cutting just under the bark of affected tissues.

OSU Plant Clinic Image, 2014.

Classic mycelial fan just under the bark of affected tissues.

OSU Plant Clinic collection, 2012.

Diagnostic mycelial fans can be seen here beneath the bark of the root crown.

Melodie Putnam, 2010.

After scraping away the dead bark, a few white mycelial plaques can be seen on the lower portion of this vine.

Photo by Everett Hansen, 1997.

Cause Podosphaera mors-uvae (formerly Sphaerotheca mors-uvae) has been reported on Ribes spp. from all states in the Pacific Northwest. In addition, Podosphaera macularis has been reported from Idaho.

Gooseberry fruit with gray patches and splits.

Photo by Jay W. Pscheidt, 1992.

As the gooseberry fruit matures, the mildew changes to a dark-brown coating that renders the berries unmarketable.

OSU Extension Plant Pathology Slide Collection, 1956.

This close up picture shows chasmothecia of the powdery mildew fungus on red currant.

OSU Extension Plant Pathology Slide Set, 1995.

Notice the diseased currant fruit are small and discolored.

Photo by Melodie Putnam, 1995.

Ornamental flowering currant can also get powdery mildew as the shoot on the right is showing.

Jay W. Pscheidt, 2012

See:

Pine, White - White Pine Blister Rust

Image related to Gooseberry and Currant (Ribes spp.)-Blister Rust

Lesions are angular and can contain either orange uredinia or black to brownish telia. Signs and symptoms develop on the underside of the leaves while only symptoms develop on the topside.

Richard A. Sniezko, 2015.

Later in the growing season, brownish hair-like structures (telia) develop.

Richard A. Sniezko, 2015.

Symptoms on the upper leaf surface (Top) and lower surface (bottom).

Robert Danchok, 2015.

Cronartium ribicola telia on underside of Ribes sp. leaf.

Zolton Bair, 2016.

See:

Blackberry (Rubus spp.) - Armillaria Root Rot

Cause Drepanopeziza ribis (asexual: Gloeosporidiella ribis), a fungus that overwinters on dead leaves. Small, mushroom-like fruiting bodies (apothecia) develop on fallen leaves in spring. They produce airborne ascospores that infect newly developing leaves. Rainy weather favors spore release and infection. Different fruiting bodies (acervuli) are produced in 3 to 4 weeks after ascospore infection.

Notice the lesions with purple borders and tan centers.

Photo by Jay W. Pscheidt, 1991.

Image related to Gooseberry and Currant (Ribes spp.)-Anthracnose

Numerous leaf spots on these currant leaves.

OSU Extension Plant Pathology Slide Set, 1978.

Cause Fusarium lateritium, a fungus. Frequently forms on twigs or branches damaged by freezing.

Symptoms Tan cankers with a purple border where tissue should be green. Peach-color elliptical fruiting bodies (sporodochia) develop within the cankered area where the lenticels are located.

Cultural control

See:

Begonia - Nematode, Foliar

See:

Greenhouse Plants, Ornamental - Impatiens Necrotic Spot

Symptoms Stunting and browning or necrosis of the central part of young gloxinia plants, resulting in death. Ringspots, veinal necrosis, and chlorotic or necrotic brown line patterns in zigzags may develop on leaves of mature plants. Local lesions may show in as little as 2 days after thrips feeding.