brown spot (Alternaria alternata) in Southern Plant Diagnostic Network

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brown spot (<em>Alternaria alternata</em>) symptoms

R.W. Samson, Purdue University, Bugwood.org

brown spot (Alternaria alternata) symptoms

brown spot (<em>Alternaria alternata</em>) symptoms

R.W. Samson, Purdue University, Bugwood.org

brown spot (Alternaria alternata) symptoms

This fungal disease appears first on the older leaves as circular, brown spots (1/4 to 1 1/4 inches in diameter) with sharply defined margins. Concentric circles (rings) are often noticeable within the spots. As the leaves approach maturity, a yellowish

R.J. Reynolds Tobacco Company , Bugwood.org

This fungal disease appears first on the older leaves as circular, brown spots (1/4 to 1 1/4 inches in diameter) with sharply defined margins. Concentric circles (rings) are often noticeable within the spots. As the leaves approach maturity, a yellowish "halo" of varying width often forms around the lesion. Lesions may merge, forming large areas of dead tissue. During humid weather, sporulation of the fungus may be abundant, giving the lesions a black, dusty appearance. Brown spot is most severe as the plant approaches maturity, and the disease progresses from the lower to the upper leaves. Disease severity depends much on the weather, the overall health of the plant, varietal tolerance, and harvest rate.

Leaf spots are brown in color, circular and enlarge to about the size of a nickel. Concentric rings can be seen within the spots and these may coalese forming irregular areas on the foliage. Disease severity is positively correlated with cloudy, wet weather. The disease occurs primarily on mature leaves often beginning on the lower leaves and progressing to other leaves higher up on the stalk.

Clemson University - USDA Cooperative Extension Slide Series , Bugwood.org

Leaf spots are brown in color, circular and enlarge to about the size of a nickel. Concentric rings can be seen within the spots and these may coalese forming irregular areas on the foliage. Disease severity is positively correlated with cloudy, wet weather. The disease occurs primarily on mature leaves often beginning on the lower leaves and progressing to other leaves higher up on the stalk.

Symptoms of the brown spot fungus first appear on the lower leaves. Spots are brown with sharply defined margins and may be surrounded by yellow halos. The primary distinguishing characteristics of brown spot are the dark concentric rings within spots that give it a target-like appearance. With magnification, reproductive structures of the casual agent are seen as tufts of black fungal spores (conidia). Under severe conditions, spots are numerous, may coalesce, and give the leaf a ragged appearance as the infected tissue falls out.

R.J. Reynolds Tobacco Company , Bugwood.org

Symptoms of the brown spot fungus first appear on the lower leaves. Spots are brown with sharply defined margins and may be surrounded by yellow halos. The primary distinguishing characteristics of brown spot are the dark concentric rings within spots that give it a target-like appearance. With magnification, reproductive structures of the casual agent are seen as tufts of black fungal spores (conidia). Under severe conditions, spots are numerous, may coalesce, and give the leaf a ragged appearance as the infected tissue falls out.

Alternaria; Brown spot on lower leaf

Department of Plant Pathology , North Carolina State University, Bugwood.org

Alternaria; Brown spot on lower leaf

Secondary organisms will colonize injured tissue following chilling injury. July 1997

Gerald Holmes, Strawberry Center, Cal Poly San Luis Obispo, Bugwood.org

Secondary organisms will colonize injured tissue following chilling injury. July 1997

brown spot (<em>Alternaria alternata</em>) symptoms on tobacco (<em>Nicotiana spp.</em>)

Virginia Tech Plant Pathology , Virginia Polytechnic Institute and State University, Bugwood.org

brown spot (Alternaria alternata) symptoms on tobacco (Nicotiana spp.)

Melon leaves with Alternaria leaf spot symptoms caused by <em>Alternaria alternata f.sp. cucurbitae </em>in the field.<em>.</em>

Howard F. Schwartz, Colorado State University, Bugwood.org

Melon leaves with Alternaria leaf spot symptoms caused by Alternaria alternata f.sp. cucurbitae in the field..

Drybean plant showing symptoms of Alternaria leaf and pod spot caused by <em>Aternaria alternata</em> on a bean field in Colombia.

Howard F. Schwartz, Colorado State University, Bugwood.org

Drybean plant showing symptoms of Alternaria leaf and pod spot caused by Aternaria alternata on a bean field in Colombia.

Lesions on pumpkin

Elizabeth Bush, Virginia Polytechnic Institute and State University, Bugwood.org

Lesions on pumpkin

Lesions on pumpkin

Elizabeth Bush, Virginia Polytechnic Institute and State University, Bugwood.org

Lesions on pumpkin

Dark mass of conidia

Elizabeth Bush, Virginia Polytechnic Institute and State University, Bugwood.org

Dark mass of conidia

brown spot (<em>Alternaria alternata</em>) sign

Jeffrey W. Lotz, Florida Department of Agriculture and Consumer Services, Bugwood.org

brown spot (Alternaria alternata) sign

brown spot (<em>Alternaria alternata</em>) symptoms on passionflower (<em>Passiflora edulis</em>)

Lesley Ingram, Bugwood.org

brown spot (Alternaria alternata) symptoms on passionflower (Passiflora edulis)

On Queen of Colorado variety.

R.W. Samson, Purdue University, Bugwood.org

On Queen of Colorado variety.