自苗栗縣造橋鄉道路邊坡蒐集得自然罹病之菟絲子植株，由罹病菟絲子組織分離得之真菌菌株，菌株編號CUSCA02，在PDA培養基上之菌絲呈灰白色，同時伴隨菌落的生長，會產生大量鮭魚肉色之分生孢子，分生孢子為單胞，直長橢圓形、兩端鈍圓至略尖，大小為15~22.5×3.8~5μm，根據分生孢子及菌落的特徵，確定此菌株為Colletotrichum sp．炭疽病菌。CUSCA02菌株之致病力探討，以不同濃度的分生孢子為接種源噴施菟絲子，在1×10^6及1×10^7 spores/ml兩個接種源濃度時，接種後15天，發病指數分別達90%及95%，其他1×10^3，1×10^4、l×l0^5，spores/ml三組的發病指數均在50%以下；三個接種濃度較高的處理組，接種後60天最後一次調查時，菟絲子植株均完全發病萎凋死亡，而兩個低濃度的處理組，發病指數達70%以下。露點時間對病害發生之影響，在保濕處理0及4小時，其病徵表現均在40%以下，處理12小時，病徵指數則達到90%，16小時以上達100%發病；在接種後14天的第二次調查，0小時的處理，病徵則加重到70%，8小時以上則達到90%以上的病徵。關於CUSCA02的寄主範圍，以1×l0^7spores/ml接種10科30種植物上，接種15天後，只有菟絲子產生病徵，對其他植物均無影響。培養基中合成培養基以OMA及1/2 OMA之產孢量最高，每皿產孢量分別為l.4×l0^9及1.1×10^9個孢子，其次為PDA、l/2PDA及MEA，分別為5.2×10^8、2.6×l0^8及1.3×l0^8個孢子；而穀類培養基以薏仁的產量最高，每公克可產生5.7×l0^8個孢子，其次為紅薏仁，可產生3.9×l0^8個孢子，糙米、蕎麥、白米、綠豆、大豆及小麥等產生1.0~2.0×10^8個孢子。由菟絲子上分離得之Colletotrichum-CUSCA02菌株對菟絲子具強致病力，造成萎凋死亡，同時本研究中也掌握了菌株產孢、露點時問、接種源強度等因素之影響，對於未來生物防治技術之開發將極具參考價值。

A Colletotrichum sp. was obtained from a diseased dodder (Cuscuta campestris) at Miao-Li Taiwan. Fungus was propagated on PDA medium at 25℃ and single-spore culture (isolate CUSCA02) was used for further study. Spore suspension was sprayed onto greenhouse grown dodder. Inoculated dodder showed severe wilting in ten days after inoculation. Effects of dew duration and inoculum potential on symptom development were also determined by greenhouse inoculation. Longer than 8 hours dew duration will lead to over 90% disease rating. Spore suspension of l×10^6 and l×l0^7 spores/ml resulted in 90 and 95% tissue necrosis of dodder in 15 days, respectively. Inoculated dodder was completely wilted in one month. Host range tests showed that Colletotrichum isolate CUSCA02 was only pathogenic to Cuscuta campestris, no symptoms were observed on 29 other plants inoculated. Spore production of artifical media was conducted using 10 types of formulated media and 10 types of grain media. Spore production were highest for oat meal agar (OMA) and cooked Job's tear, producing 1.36×10^9 spores/dish and 5.65×10^8 spores/g, respectively. Our suty indicated isolate CUSCA02-Colletotrichum sp. is a promising biological control agent for dodder.