本土昆蟲病原真菌防治秋行軍蟲的應用潛力與其對非生物逆境的耐受性

Application potential of native entomopathogenic fungi in controlling Spodoptera frugiperda and their tolerance to abiotic stresses

秋行軍蟲（Spodoptera frugiperda）於2019入侵台灣後，嚴重危害玉米及高粱等糧食作物，其幼蟲啃食玉米葉片、花穗、鑽進生長點取食，導致產量及品質下降。目前噴灑化學農藥是主要的防除方法，但長期施用易產生抗性，因此本研究目的是利用昆蟲病原真菌（Entomopathogenic fungi, EPF）作為防治資材，篩選具防治秋行軍蟲潛力與對紫外線、農藥等非生物逆境具有耐受性之菌株，供試菌株包括爪哇擬青黴菌（Cordyceps javanica）PMEPF02、白殭菌（Beauveria bassiana）PMEPF11、PMEPF23。以浸葉法測試上述三支菌株對秋行軍蟲幼蟲的致病性，結果顯示PMEPF02致病力最高，LT50僅需約1.69天，其次依序為PMEPF11及PMEPF23，LT50分別為3.27、6.11天。在紫外線這種物理逆境中，以PMEPF11耐受性最佳，其在UV-B處理15分鐘後仍有42%發芽率；在農藥這種化學逆境測試中，結果顯示玉米推薦用藥的殺菌劑普克利及除草劑固殺草、百速隆三者皆抑制三株昆蟲病原真菌的孢子發芽；而白殭菌PMEPF11與蘇力菌商品（福祿寶）混合使用不僅能提升殺蟲效果，也使LT50縮短至0.68天。綜上所述，白殭菌PMEPF11為具防治秋行軍蟲潛力與抗逆境之菌株，且與商品福祿寶混合使用可縮短致死時間。

Since fall armyworm (Spodoptera frugiperda) invade into Taiwan in 2019, this pest has severely damaged food crops such as corn and sorghum. The larvae chew on corn leaves, tassels, and bore into the growth points to feed, resulting in reduced yield and quality. Currently, chemical pesticides are the primary control method, but long-term use can lead to development of resistance. Therefore, this study aims to use entomopathogenic fungi (EPF) as control agents, selecting strains with potential to control the fall armyworm and tolerate to different abiotic stresses. The tested strains included Cordyceps javanica PMEPF02, Beauveria bassiana PMEPF11, PMEPF23. The pathogenicity of the five strains against fall armyworm larvae was tested using the leaf-dip method. The results showed that PMEPF02 strain had the highest pathogenicity, with an LT50 of only 1.69 days. Followed by PMEPF11, and PMEPF23, with LT50 values of 3.27, and 6.11 days, respectively. In ultraviolet tests, PMEPF11 exhibited the best tolerance; after 15 minutes of UV-B treatment, it still had a germination rate of 42%. Agricultural chemicals, including the recommended fungicide propiconazole and herbicides glufosinate-ammonium and pyrazosulfuron-ethyl for corn, inhibited conidia germination of the four test strains. Additionally, combining B. bassiana PMEPF11 with the commercial Bacillus thuringiensis subsp.aizawai strain NB-200 product not only enhanced the insecticidal effect but also reduced the LT50 to 0.68 days. In summary, B. bassiana PMEPF11 is a potential strain for controlling the fall armyworm, and combining it with the commercial B. thuringiensis product can shorten the lethal time.