利用球孢白殭菌防治香蕉假莖象鼻蟲（鞘翅目：象鼻蟲科）：有效菌株篩選與香蕉假莖注射法之應用

Biological Control of the Banana Pseudostem Weevil Odoiporus longicollis (Oliver, 1807) (Coleoptera: Curculionidae) by Using Entomopathogenic Fungi Beauveria bassiana: Effective Strain Screening and Application of Pseudostem Injection

香蕉經常受到香蕉假莖象鼻蟲（Odoiporus longicollis（Oliver, 1807））的危害，使植株內部組織結構破壞甚至整株倒伏，造成嚴重經濟損失。本研究從田間收集了五個受白殭菌感染之昆蟲（香蕉象鼻蟲為主）樣本進行有效菌株分離篩選，並加入唯一市售白殭菌僵僵好（A1）作為參考進行比較。根據ITS、nrLSU、tef1-α、rpb1及rpb2等五段基因序列建立親緣關係樹，可以確定本研究於野外所採集之樣本分離株皆為球孢白殭菌（Beauveria bassiana）。於實驗室內進行試驗，菌株SF404、SF303、SF124及A1於3×109 conidia/mL濃度下對香蕉假莖象鼻蟲成蟲之致死率在12天後分別可達93.3、90.0、90.0及53.3%。在24℃定溫下以PDA培養環境下，各菌株之孢子萌發率在24 hr皆可達到90%以上。在15天培養後之菌落直徑於菌株SF124、SF303及SF404分別為5.38、5.25及4.83 cm。於24℃定溫下SF124、SF303及SF404三菌株之單位面積產孢量分別為2.39×108、2.18×108及2.05×108 conidia/cm2。於香蕉假莖注射1×107、1×108及1×109 conidia/mL濃度之球孢白殭菌SF124孢子懸浮液，兩週後幼蟲之死亡率分別為45.0、65.0及95.0%。注射1×108 conidia/mL濃度之SF124孢子懸浮液並放置0、14及28天後接種幼蟲，兩週後之死亡率分別為65.0%、35.0%及25.0%。基於上述等試驗結果，本研究所篩選之菌株與香蕉假莖注射法頗具潛力開發為防治香蕉假莖象鼻蟲之新選擇。

Banana plants were often attacked by the stem borer, banana pseudostem weevil, Odoiporus longicollis (Oliver, 1807), causing severe stem damage and economic loss. In this study, we collected five infected insects from the field and screened for effective strains compared with Taiwan's only commercial product, Beauveria bassiana (strain A1). Using ITS, nrLSU, tef1-α,rpb1, and rpb2 sequences, the species of Beauveria isolates collected from the field are confirmed as B. bassiana. The fatality rate of strains SF404, SF303, SF124, and A1 was respectively 93.3, 90.0, 90.0, and 53.3% at 3×109 conidia/mL concentration on adult banana pseudostem weevil after 12 days’infection. The spore germination rate of strains SF124, SF303, and SF404 can all reach over 90% after 24 hr incubation on PDA medium at 24℃. The colony diameter of strains SF124, SF303, and SF404 were 5.38, 5.25, and 4.83 cm after 15 days of incubation on a PDA medium at 24℃. The spore production rate at 24℃incubations for strain SF124, SF303, and SF404 were followed by 2.39×108, 2.18×108, and 2.05×108 conidia/cm2. The mortality of banana pseudostem weevil by applying pseudostem injection in 1×107, 1×108, and 1×109 conidia/mL concentration of strain SF124 spore suspension was 45.0, 65.0, and 95.0, respectively. After standing for 0, 14, and 28 days of 1×108 conidia/mL SF124 spore suspensions pseudostem injection and inoculation with banana pseudostem weevil larva, the mortality was 65.0, 35.0, and 25.0%, respectively. Based on the experimental results, these new strains of B.bassiana and pseudostem injection provide a potential microbialagent and new ways to control banana pseudostem weevil.