東方果實蠅雄蠅對現行誘殺劑及芬普尼感受性之檢測

Abstract

東方果實蠅 (Bactrocera dorsalis (Hendel)) (雙翅目：果實蠅科) 為東南亞與南太平洋地區的果樹重要害蟲。甲基丁香油 (methyl eugenol) 對東方果實蠅雄蠅具強烈誘引效果，與殺蟲劑搭配的混合製劑常用於滅雄防治技術與害蟲偵察及監測。國內在誘殺劑的選用上，採乃力松搭配甲基丁香油作為唯一推薦用法，並已推行數十年之久。然而，長期施用誘殺劑的情況下，田間果實蠅族群無論對於甲基丁香油或乃力松之感受性，皆可能有下降之趨勢，進而削弱誘殺劑之防治效力。故本研究針對誘殺劑對東方果實蠅雄蠅之感受性進行探討，調查野外雄蠅對甲基丁香油於遠、近距離上的感受性；以標示再捕試驗評估抗藥性對含毒甲基丁香油誘殺效力的影響；另以焦磷酸定序技術，偵測原野外品系雄蠅與標放中被誘捕的野外品系雄蠅之抗性相關基因點突變頻度，藉此探討抗性較高的雄蠅自誘殺器逃逸之可能性。網籠試驗結果顯示，宜蘭、彰化野外品系、藥劑敏感性品系及乃力松抗性品系的雄蠅，對於甲基丁香油的近距離感受性皆相當高，誘引率皆可逾 90%。然而，當野外雄蠅於曾交尾過的情況下，對於甲基丁香油的感受性會大幅下降。標放試驗中，當以含乃力松之甲基丁香油為誘殺劑，無論兩野外品系或乃力松抗性品系之再捕率，皆顯著低於感性品系。然而，改用含芬普尼之甲基丁香油，乃力松抗性與感性品系的再捕率間則無顯著差異。單獨使用甲基丁香油進行誘引，被誘引之雄蠅能自由進出改良型麥氏誘殺器。此外，誘殺器內被捕捉的標記雄蠅之抗性基因頻度，顯著低於原野外品系。上述結果顯示，當雄蠅具有一定程度的乃力松抗性，確實有較高機會得以自誘殺器內逃出。另根據焦磷酸定序結果，推測造成野外雄蠅再捕率較低的原因係與乃力松抗性有關。根據本研究結果，臺灣田間果實蠅族群應僅存在 3-4% 對甲基丁香油不敏感或感受性較差的雄性個體，對於現今以甲基丁香油為誘引物質之防治現況應無甚大影響。另一方面，宜蘭、彰化野外雄蠅之有機磷抗性相關點突變頻度亦已有 60%，也由於國內使用的誘殺劑種類單一，因此，亟需評估並找尋替代藥劑，以解決抗藥性對滅雄防治造成的問題。

The oriental fruit fly, Bactrocera dorsalis (Hendel) (Diptera: Tephritidae), is an economically important pest of fruit trees in Southeast Asia and the South Pacific area. Male oriental fruit flies are strongly attracted to methyl eugenol (ME), therefore ME is often used with insecticides as part of male annihilation techniques, pest monitoring and detection. In Taiwan, naled-intoxicated ME is the only recommended attract-and-kill agent, and has been used for decades. When using the attract-and-kill agent for a long period, however, the susceptibility of male flies in wild populations to methyl eugenol and naled both may decrease, and decline control efficacy of naled-intoxicated ME. Therefore, the main goal of the present study is the susceptibility of the male oriental fruit flies to intoxicated methyl eugenol, to investigate responsiveness of wild male flies to ME with long- or close-range attraction; assess the effects of naled resistance in male flies on the attract-and-kill efficiency of naled-intoxicated ME by mark-release- recapture experiments. Also, in order to understand the possibility that males with higher naled resistance have higher likelihood of escaping from traps, the proportions of resistance associated mutations in wild male flies from original populations or trap-captured were detected using pyrosequencing. Results of cage experiments revealed that the responses of wild (Yilan and Changhua), susceptible, and naled resistant strains were all very high in close-range attraction, and capture rates of above strains were more than 90%. After the wild males mated, however, the responses of those flies became much lower. The results of mark-release-recapture experiments showed that the recapture rates of the wild and naled-resistant strains were significantly lower than those of the susceptible strain when using naled-intoxicated ME as attract-and-kill agent. Nevertheless, there were no significant differences between the recapture rates of resistant and susceptible strains when using fipronil-intoxicated ME. Captured flies could escape from improved McPhail traps when only ME was used. Also, the proportions of resistant alleles in marked wild males captured in traps were lower than those in males from original wild populations. The above results revealed that flies with higher naled resistance are more likely to escape from traps using naled-intoxicated ME. According to the results of pyrosequencing, the resistance may be the explanation for lower wild strain recapture rates in field experiments. In conclusion, paucity (3-4%) of males with non- or lower- responsiveness to ME in wild populations may not affect the attractant efficiency of flies. On the other hand, assessing and searching alternative insecticide to replace naled is important, given that the proportions of mutation associated with organophosphate resistance of wild flies (Yilan and Changhua) were about 60% and there is only one kind of attract-and-kill agent used in Taiwan.