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Texas Phoenix Palm Decline is a plant disease caused by a phytoplasma, ''Candidatus'' Phytoplasma palmae.〔Elliott, Monica. "Emerging Palm Diseases in Florida." HortTechnology 4th ser. 19.4-19 (2009): 717-18. High Wire Press. Web. 1 Dec. 2012. http://horttech.ashspublications.org.ezproxy.library.wisc.edu/content/19/4/717.full.pdf+html〕〔Harrison, Nigel A., and Monica L. Elliot. "Texas Phoenix Palm Decline." University of Florida IFAS Extension. Plant Pathology Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida, n.d. Web. 23 Oct 2012. The TPPD strain is classified as group 16SrIV, subgroup D (16SrIV-D) and LY:16SrIV-A.〔Harrison, Nigel A., and Monica L. Elliot. "Lethal Yellowing of Palm ." University of Florida IFAS Extension. EDIS, n.d. Web. 23 Oct 2012. Several palms susceptible to the phytoplasma have been documented, including: ''Phoenix canariensis'', ''Phoenix dactylifera'', ''Phoenix sylvestris'', ''Phoenix reclinata'', ''Sabal palmetto'', and ''Syagrus romanzoffiana''. Prior to 2006, Lethal Yellowing was the only other strain of phytoplasma known to attack palm trees in Florida. The introduction of this disease has left the state of Florida struggling to control the potential damage to palm trees in landscapes statewide.〔Harrison, Texas Phoenix Palm Decline〕〔Harrison, N. A., and E. E. Helmick. "Blackwell Publishing Ltd First Report of a Phytoplasma-associated Lethal Decline of Sabal Palmetto in Florida, USA."Annals of Applied Biology 153.1 (2009): 792. Plant Disease. 1 Dec. 2012 〕 == Symptoms == It has been observed to almost exclusively attack Canary Island Palm, but is seen on other species.〔Elliot, Emerging Palm Diseases in Florida〕 Since 2009, Texas Phoenix Palm Disease is known to severely affect the ''Phoenix spp.'' and ''Sabal spp.'' palm trees: Canary Island date palm, Silver or Sylvester date palm, Queen palm, Sabal palm, and Cabbage palm. All of these trees have been observed to have the same symptoms. The complete host range of this phytoplasma strain is not yet known.〔〔Broschat, Timothy K., Monica L. Elliot, and Ian Maguire. "Texas Phoenix Palm Decline." A Resource for Pests and Diseases of Cultivated Palms. University of Florida, Institute of Food and Agricultural Sciences (UF/IFAS), and the Center for Plant Health Science and Technology (USDA/APHIS/PPQ/CPHST), 1 2010. Web. 23 Oct 2012. http://itp.lucidcentral.org/id/palms/symptoms/Texas_Phoenix_Palm_Decline.htm〕 If the palm tree is mature enough to produce fruit, it will experience two major symptoms. Premature drop of the majority or all of the fruit, within a short time period (about three days), is an obvious symptom. Soon after this, the flowers become necrotic.〔 However, these symptoms can only be observed during flowering and fruiting season, and if the flowers have not been trimmed from the tree.〔 At any palm age, early infection will show discoloration of the foliage, starting at the tips of the oldest leaves. The leaf colors change from the normal green to different shades of reddish-brown, to dark brown.〔 Declining palm trees are characterized by a large number of discolored leaves in the lower and mid-crown region of the tree.〔Phyto Harrison, First Report of Phytoplasma〕 When about 1/3 of the oldest leaves become discolored, the spear leaf will die, displaying a tan, rather than green color. The spear leaf is the youngest leaf, generally seen in the center of the canopy. In obvious situations, the dead spear life can be seen hanging down or broken off of the canopy. This indicates that the apical meristem is dead and there will be no new leaf production or growth. In most cases, without close examination, the spear leaf will not be easy to find or observe if it is still alive. Occasionally, when the spear leaf dies, some palms experience root rot. This is a major symptom that differentiates TPPD from Lethal Yellowing, since LY does not experience root decay.〔 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「Texas phoenix palm decline」の詳細全文を読む スポンサード リンク
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