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Raspberry Leaf Spot is a plant disease caused by ''Sphaerulina rubi'', an ascomycete fungus. Early symptoms of infection are dark green spots on young leaves. As the disease progresses, these spots turn tan or gray in color. Disease management strategies for Raspberry Leaf Spot include the use of genetically resistant raspberry plant varieties and chemical fungicide sprays. Raspberries are an important fruit, mainly grown in Washington, Oregon and California.〔Hanson, Eric, Mike Von Weihe, Annemiek Schilder, Ann Chanon, and Joseph Scheerens. "High Tunnel and Open Field Production of Floricane- and Primocane-fruiting Raspberry Cultivars." HortTechnology 21.4 (2011): 412-18. Web. http://horttech.ashspublications.org/content/21/4/412.full.pdf+html〕〔Geisler, Malinda. Agricultural Marketing Resource Center, Iowa State University http://www.agmrc.org/commodities__products/fruits/raspberries/〕 Although they are also grown in the Midwest and northeastern states, the output is not nearly as great due to the colder weathers and shorter growing seasons.〔 ''S. rubi'' prefers warmer and wetter conditions, which can make raspberry production very difficult in California. == Hosts and symptoms == A Raspberry Leaf Spot infection initially causes dark green circular spots on the upper side of young leaves, which will eventually turn tan or gray.〔Behrendt, Chad J. Raspberry Diseases. University of Minnesota Extension, Department of Plant Pathology, 2013. http://www.extension.umn.edu/distribution/horticulture/DG1152.html〕 These spots are typically 1–2 mm in diameter, but can get as big as 4–6 mm.〔Demaree, J. B., Wilcox, Marguerite S. “The fungus causing the so-called ‘ Septoria leaf spot disease ‘ of Raspberry.” Phytopathology 1943 Vol. 33 No. 11 pp. 986–1003. http.www.cabdirect.org/abstracts/19441100325.html;jsessionid=A9733F609B4A57FB2E1BC645CCF7F220〕 More severe infections can cause leaves to drop prematurely in the late summer and early fall.〔Plant and Insect Diagnostic Clinic. "Raspberry Leaf Spot." Iowa State University Extension and Outreach. National Plant Diagnostic Network, 30 Mar. 2012. Web. 5 Oct. 2013. 〕 Due to the loss of leaves, infected raspberries are more susceptible to winter injury.〔Behrendt, Chad J. “Raspberry Diseases.” University of Minnesota Extension, Department of Plant Pathology, 2013. 〕 As a result, Raspberry Leaf Spot may not only reduce yield in season, but cause lasting consequence into the next season. The symptoms of Raspberry Leaf Spot are similar to the symptoms of Raspberry Anthracnose. The best way to differentiate between the two fungal diseases is to inspect the stems of the plant. Stem lesions are indicative of Raspberry Anthracnose. In 1943, it was discovered that ''S. rubi'' only infects raspberry plants.〔 Previously, the pathogen had also been blamed for leaf spot on blackberry and dewberry. However, Demaree and Wilcox demonstrated the raspberry pathogen could not cause leaf spots on blackberry or dewberry.〔 The similar pathogens were also differentiated as perfect and imperfect, as the Blackberry Leaf Spot pathogen didn’t have a known sexual stage. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Raspberry leaf spot」の詳細全文を読む スポンサード リンク
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