Image Number: 1440024

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.
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Image location:
United States


Kingdom: Fungi
Phylum: Ascomycota
Subphylum: Pezizomycotina
Class: Dothideomycetes
Subclass: Dothideomycetidae
Order: Pleosporales
Family: Pleosporaceae
Genus: Alternaria
Subject: Alternaria alternata (Fr.) Keissl.


Kingdom: Plantae
Phylum: Magnoliophyta
Class: Magnoliopsida
Subclass: Asteridae
Order: Solanales
Family: Solanaceae
Genus: Nicotiana
Subject: Nicotiana tabacum (burley type) L.
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Image uploaded:
Monday, January 1, 1990
Image last updated:
Tuesday, May 17, 2011