番石榴果實新病害黑星病及其他病害生態調查

Ecological survey of guava new fruit rot--Phyllosticta rot (black spot) and other fruit rots

自從泰國拔品種成為國內的主要栽培品種之後，果實迭生新病害，並造成嚴重損失。一種過去未紀錄之病害，番石榴果肉出現藍黑色，病斑邊緣木栓化及容易脫落，病徵易與其他病害區隔，稱為黑星病（Phyllosticta psidiicola）。調查果實其他種類病害，則以瘡痂病（Pestalotiopsis psidii）較為常見，調查中發生率占第二位，炭疽病（Colletotrichum gloeosporoides）及疫病（Phytophthora parasitica）則發生較少。根據一年以上的調查，高雄縣秋季果實黑星病發病率最高，冬季最低，春、夏季居中；相對於黑星病，瘡痂病則於冬季發病率最高，秋季最低，春夏約略相等；炭疽病則以二個夏季在全程調查中，發病率較高。由調查病果發現果實採收後置於室內五天，黑星病病徵比例增加，具有潛伏感染的現象。二種主要品種珍珠拔及水晶拔果實黑星病發病率各達80.2%及94.5%，顯示此種病害在南部地區已成一個嚴重的病害因且造成重大的損失，四種主要病害種類在珍珠拔上皆較水晶拔普遍發生。從番石榴園採集孢子的資料得知年度內可多次捕捉到黑星病子囊孢子，調查中未曾發現或捕獲黑星病的分生孢子，此一現象是否代黑星病主要感染源由子囊孢子而來，仍須進一步觀察。

"Diseases of guava have become a serious problem since the Thai variety of guava has been grown and become popular in Taiwan. New fruit rot disease has caused great losses to guava production. As to particular symptoms on guava fruit tissue, the tissue turns deep blue to black after being infected, and the margin of the fruit rot is easily distinguishable from healthy tissue. Sometimes, tissue with fruit rot forms a cavity because of the rotting fruit tissue. As described above, this is black spot new disease called Phyllosticta rot of guava fruit. In the meantime, Pestalotiopsis rot has become less severe, and Colletotrichum and Phytophthora are minor diseases compared to Phyllosticta rot. In a more than 1-year field survey, Phyllosticta rot was more severe in autumn than in spring and summer. In winter, there was a low incidence in guava orchards in Kaohsiung County. However, Pestalotiopsis rot showed a reverse result in field surveys, with guava fruit showing a high incidence in winter. Colletotrichum rot showed a relatively high incidence in summer. Phyllosticta rot caused a higher incidence 5 days after harvest compared to the harvest day. This phenomenon shows that Phyllosticta rot has a latent infection on guava fruit. Phyllosticta rot was detected at 80.2 % and 94.5 % incidences in the pearl and crystal guava varieties, respectively. These results show that black spot has become an important disease and causes great losses in Taiwan. It was also found that the 4 fungal diseases mentioned above were more common or epidemic on the pearl variety than on the crystal variety. When airborne spores were collected by Burkard's spore trapper, plenty of ascospores of Guignardia psidii (an anamorph of Phyllosticta psidiicola) were found in August; however, conidia of P. psidiicola were not found in the survey. This points out that ascospores might act as an important route of disease transmission."