Author
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Chellemi, Daniel |
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Submitted to: Book Chapter
Publication Type: Book / Chapter Publication Acceptance Date: 1/20/2006 Publication Date: N/A Citation: N/A Interpretive Summary: Zonate leaf spot is primarily a foliar disease of tomato but has been observed infecting stems and fruit. It occurs sporadically in the field but on occasion can cause significant defoliation and yield reductions in localized areas. The disease was first described on maple (Acer spp.) in 1947. Subsequently, it has been reported on 73 species comprising 36 different families of vascular plants including woody perennials and annual succulents. On tomato, zonate leaf spot has a wide geographic distribution in the eastern United States ranging from New York and Pennsylvania to Florida. Zonate leaf spot derives it name from the occurrence of large, circular leaf lesions with distinct concentric rings. Initially the leaf lesions are light tan in color and the concentric rings are symmetrical appearing as a ‘bulls eye’. Initial lesions are 5-10 mm in diameter and continue to expand by adding more rings. Lesions may reach 30 mm in diameter. Eventually lesions will coalesce causing leaves to senesce. Leaf lesions caused by Zonate leaf spot may be distinguished from those caused by early blight (Alternaria solani) by the following characteristics: the concentric rings are more symmetrical than those caused by early blight, no distinct chlorosis is associated with the lesions and leaf lesions are not localized near the bottom of the tomato canopy. Lesions can also form on the stems. Fruit infections appear to result from expansion of lesions on the sepals and peduncle. Following periods of high humidity, large pyramid-shaped reproductive structures form on the older leaf lesions. These structures, referred to as fruiting bodies are visible with a powerful hand lens or under low magnification with a stereo, dissecting microscope. Sclerotia are occasionally observed on the peduncle end of fruit infections. Technical Abstract: Zonate leaf spot derives it name from the occurrence of large, circular leaf lesions with distinct concentric rings. Initially the leaf lesions are light tan in color and the concentric rings are symmetrical appearing as a ‘bulls eye’. Initial lesions are 5-10 mm in diameter and continue to expand by adding more rings. Lesions may reach 30 mm in diameter. Eventually lesions will coalesce causing leaves to senesce. Leaf lesions caused by Zonate leaf spot may be distinguished from those caused by early blight (Alternaria solani) by the following characteristics: the concentric rings are more symmetrical than those caused by early blight, no distinct chlorosis is associated with the lesions and leaf lesions are not localized near the bottom of the tomato canopy. Lesions can also form on the stems. Fruit infections appear to result from expansion of lesions on the sepals and peduncle. Following periods of high humidity, large pyramid-shaped reproductive structures form on the older leaf lesions. These structures, referred to as fruiting bodies are visible with a powerful hand lens or under low magnification with a stereo, dissecting microscope. Sclerotia are occasionally observed on the peduncle end of fruit infections. |
