評估本土分離光桿菌防治入侵紅火蟻之潛力

Evaluation and Photorhabdus luminescens (Taiwan isolate) as a potential agent against invasive fire ant Solenopsis invicta

曾鈺芳(Yu-Fang Tseng)

指導教授 ： 楊景程

共同指導教授 ： 張雅君(Ya-Chun Chang)

國立臺灣大學/生物資源暨農學院/植物醫學碩士學位學程/碩士(2013年)

https://doi.org/10.6342/NTU.2013.02157

摘要

入侵紅火蟻 (red imported fire ant, RIFA; Solenopsis invicta) 於 2003 年首次在台灣發現，並快速於北台灣擴散，相關單位立即投入大量資源展開滅絕計畫 (eradication program)，但可能因經費、氣候或地形複雜等因素導致成效未如預期，顯示防治計畫急需調整，根據美國農部 (United States Department of Agriculture) 提出之區域整合防治 (area-wide control) 概念，將藥劑結合生物防治能有效降低火蟻族群並防止再入侵的發生，有鑑於台灣火蟻族群之原生天敵有限，本研究即針對台灣特有之土棲性蟲生線蟲異小桿線蟲 (Heterorhabditis bravicaudis) 之腸道內共生菌-光桿菌 (Photorhabdus luminescens) 進行防治潛力評估。試驗結果發現，餵食光桿菌培養液混拌糖水或是菌體混拌糖水製成之液狀餌劑，皆會導致火蟻成蟲死亡，但無法在餵食菌體混伴糖水組別中之職蟻體內回分到光桿菌存在。餵食光桿菌培養液之幼蟲則會呈現皺縮、變色或是軟爛，平均約 5 天後死亡；培養液餵食職蟻試驗死亡率於第 10 天內可達 94.7%；小型蟻巢試驗中 10 天死亡率則高達 98.9%，並發現光桿菌的殺蟲物質可經由交哺作用 (trophallaxis) 造成巢內幼蟲死亡。利用半薄切片 (semi-thin section) 針對餵食培養液幼蟲體內結構進行細部病理檢視，發現死亡幼蟲之腸道破碎，推測可能與光桿菌培養液中之二次代謝物中 (例如 Makes Caterpillars Floppy Toxins, Mcf) 引起的細胞凋亡 (apoptosis) 有關。綜觀本研究結果，光桿菌菌體雖無法於蟻巢個體間傳播，不利於生物防治施用，但光桿菌分泌之多種二次代謝產物及殺蟲蛋白，可藉由交哺廣佈至蟻巢中其他職蟻、幼蟲甚至蟻后，弱化或是殺死火蟻巢。未來研究可針對特定代謝物或是殺蟲蛋白進行純化分離，發展新型殺蟲藥劑，降低化學藥劑成本或是配合其他微生物天敵共同施用，讓台灣火蟻防治策略更加完整且能更靈活運用。

關鍵字

入侵紅火蟻 ； 光桿菌 ； 整合防治

並列摘要

Red imported fire ant (Solenopsis invicta) was introduced into Taiwan in 2003 and spread rapidly across the northern Taiwan since introduction. To minimize negative impacts by fire ants, large-scale eradication program with intense bait broadcast was immediately carried out by multiple government agencies. It seems, however, the infested area continues expanding with the presence of numerous sporadic sites of fire ants outside the core infestation. Such situation can be considered as an endless dilemma of fire ant control and attributes to re-colonization by fire ants into bait-treated area from surrounding populations. Along with reducing budget recently, the eradication program therefore is no longer a feasible option, and long-term containment then appears to be a new management perspective. It has been suggested that area-wide suppression of fire ants is even more promising if toxic baits are teamed up with self-sustaining biological control agents, thus indicating that employment of biocontrol agents as supplement for bait treatment may hold the key for successful containment of fire ants in Taiwan. Paucity of natural enemies therefore leads to the present study where Photorhabdus luminescens (Taiwan isolate), a symbiotic bacterium harbored by a soil-born entomopathogenic nematode Heterorhabditis bravicaudis, and its potential were evaluated as a microbial control agent. Failure to re-culture the bacterium from cadavers of workers fed with non-filtered bacteria broth suggests bacterium-derived secondary metabolites as possible causes for such mortality. The average mortality reaches 94.66% in 10 days as workers are fed with liquid bait with bacterially filtered broth, while 98.94% for treated small colony fragments. Larvae in small colony fragments fed with filtered bacterial broth possess shriveled body and were found dead in few days after treatment, suggesting that they may receive secondary metabolites from nestmate through trophalallaxis, which is critical for controlling social insects. Semi-thin section reveals that most of internal tissue structure of brood cadaver is tattered or smashed, which possibly results from apoptosis induced by bacterium toxin (e.g., Makes Caterpillars Floppy Toxins, Mcf). Overall speaking, the present study shows that the secondary metabolites form P. luminescens are effective in controlling fire ant and are favored over bacterium itself in term of pathogen transmission simply because the digestive tract of ant workers are too narrow to take bacterium in. Furthermore, the secondary metabolites form P. luminescens may represent a new class of pesticides, and future studies should focus on its flexibility and compatibility with other pathogens or with conventional management approaches of fire ants .

並列關鍵字

IPM ； red imported fire ant ； Photorhabdus luminescens

參考文獻

洪裕堂、林仁偉、楊景程、吳文哲、石正人、林宗岐。 2006。 利用餌劑防治入侵紅火蟻 (Solenopsis invicta) 試驗初探。台灣昆蟲 26: 57-67。

施錫彬、蘇冠中。2006。餌劑對入侵紅火蟻防治試驗。桃園農業改良場研究彙報 (60)。

許弘瑋。2010。入侵紅火蟻雙順子病毒台灣分離株之特性及對入侵紅火蟻之影響。國立臺灣大學昆蟲學研究所博士論文。

Hsu, H. W. 2010. Characterization of a Dicistrovirus Taiwan Isolate, SINV-1 (TW), and its impact on the red imported fire ant, Solenopsis invicta, in Taiwan. Ph. D thesis.

Yang, C. C., Y. C. Yu, S. M. Valles, D. H. Oi, Y. C. Chen, D. D. Shoemaker, W. J. Wu, and C. J. Shih. 2010. Loss of microbial (pathogen) infections associated with recent invasions of the red imported fire ant Solenopsis invicta. Biological Invasion 12: 3307-3318.