紅龍果莖潰瘍病病原特性及防治研究

Abstract

紅龍果為我國新興果樹，已知病害除了有由病毒引起的病毒病害外，尚有由Biporlaris、Alternaria、Fusarium、Phomopsis 及Penicillium引起之果腐病；由Colletotrichum 引起之炭疽病；由Gilbertella persicaria 引起之濕腐病以及由Neoscytalidium dimidiatum 引起之紅龍果莖潰瘍病(pitaya stem canker)，其中莖潰瘍病為近年來紅龍果最重要之病害，嚴重限制紅龍果的生產。本病害已普遍在全台紅龍果產區中蔓延，初期在莖部呈現小黃點，後漸擴展為橘色及褐色斑並產生突起之柄子器，嚴重時會導致莖部腐爛及果實乾腐裂果。本研究於田間接種Neoscytalidium dimidiatum 分生胞子於紅龍果植株莖蔓上，結果顯示不論是否進行傷口接種，紅龍果肉質莖均會於接種後2週顯現初期潰瘍病徵且新稍為主要感染時期；25–35℃為本病原菌絲生長之最適溫，25–40℃為分生胞子之發芽適溫。室內藥劑篩選發現賽普護汰寧、亞托待克利及得克利等藥劑處理皆可有效抑制菌絲生長，而在免得爛、三氟敏、百克敏、亞托敏、亞托待克利及克熱淨等藥劑稀釋溶液處理下則可顯著降低病原菌之胞子發芽率。前述藥劑皆已推薦於紅龍果炭疽病之防治，可作為田間防治紅龍果莖潰瘍病之用。綜合言之，本病之防治方法為使用健康種苗、注意田間衛生，確實清除罹病組織、發病園勿使用上方噴灌以避免病原傳播以及使用化學藥劑防治等。 Pitaya (Hylocereus undatus and H. polyrhizus Britt. & Rose) is an emerging fruit crop and cultivated around 1,000 hectaresin Taiwan. The diseases of pitaya include virus diseases, fungal fruit rot diseases caused by Bipolaris, Alternaria, Fusarium, Phomopsis, and Penicillium, anthracnose disease caused by Colletotrichum, wet rot disease caused by Gilbertella persicara, and stem canker disease caused by Neoscytalidium dimidiatum. Among these diseases, stem canker was an emerging disease limiting the production of pitaya in recent years and expanded quickly to most commercial planting areas in Taiwan. Symptoms on the stem were small, circular, sunken, orange spots that developed into cankers. Pycnidia were erumpent from the surface of the cankers and the stems subsequently rotted. We inoculated pitaya stems with N. dimidiatum in the field. Initial canker lesion was first appeared2 weeks after wound/unwound inoculation, and the formation of black pycnidia was observed 6 weeks after inoculation. The optimal temperatures for mycelial growth and spore germinationof N. dimidiatum were 25–35℃and 25–40℃, respectively. Mycelial growth was effectively inhibited by Cyprodinil + Fludioxonil, Azoxystrobin + Difenoconazole and Tebuconazole. Spore germinationof N. dimidiatum was inhibited by 80% Metiram, 50% Trifloxystrobin, Pyraclostrobin, Azoxystrobin, Azoxystrobin + Difenoconazole and Iminoctadine. These fungicides have been recommended for thecontrol of anthracnose of pitaya, and could also be used to control stem canker of pitaya in the field. The strategies for control this disease include use of disease-freeseedlings, field sanitation, avoidingspray irrigation, and fungicide applications.