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Phomopsis blight of juniper
''Phomopsis'' blight of juniper is a foliar disease discovered in 1917 caused by the fungal pathogen ''Phomopsis juniperovora''. The fungus infects new growth of juniper trees or shrubs, i.e. the seedlings or young shoots of mature trees. Infection begins with the germination of asexual conidia, borne from pycnidia, on susceptible tissue, the mycelia gradually move inwards down the branch, and into the main stem. Management strategies mainly include removing and destroying diseased tissue and limiting the presence of moisture on plants. Junipers become resistant to infection as they mature and the young yellow shoots turn dark green. Preventative strategies include planting only resistant varieties and spraying new growth with fungicide until plants have matured.
== Hosts and symptoms ==
''Phomopsis'' blight of juniper commonly infects the eastern red cedar, savin (''Juniperus sabina''), creeping juniper, and rocky mountain juniper plants (''Juniperus scopulorum''), but also has the ability to infect Chinese juniper and common juniper to varying degrees.〔(UofI: Phomopsis Blight )〕
Although spores from diseased juniper plants infect healthy hosts in the fall, symptoms are usually not seen until late winter or early spring. Often the first symptom noted is the browning of needle tips as the disease invades young, vulnerable tissue. New shoots that are normally yellow-green in color begin to turn to red brown and then ashen gray as they slowly die from the fungal disease. The infection progresses inward from the tips of branches and forms small lesions at points where infected tissue meets healthy tissue. Lesions then girdle limbs less than one centimeter in diameter, effectively killing the entire branch.〔(USDA FS: Phomopsis Blight of Junipers )〕 Repeated blighting occurring in early summer may also result in abnormal bunching caused by ''Moniliophthora perniciosa'' or more commonly known as Witches Broom.〔(KSU: Juniper Diseases )〕
''Phomopsis'' blight of juniper only infects young, succulent tissue such as immature leaves or branches. Junipers that have been wounded or freshly pruned junipers also yield higher infection rates due to an increase of new growth. Mature juniper plants lack these characteristics and are usually immune to infection. On average, their branches also have larger diameters, which allow lesions to heal rather than become girdled and kill the terminal branch.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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