Abstract In this study, we attempted to demonstrate the enhanced insecticide activity of boric acid on Autographa californica multiple nucleopolyhedrovirus (AcMNPV) and Spodoptera exigua multiple nucleopolyhedrovirus (SpeiMNPV). The data show that the LT50 value for third-instar Trichoplusia ni (T. ni) larvae was reduced from 4.1 days for AcMNPV alone to 3 days in the presence of 2% boric acid. Similarly, the LT50 value for third-instar S. exigua Hubner larvae was also reduced from 6.2 days for SpeiMPNV alone to 5.3 days in the presence of 2% boric acid. In addition, increasing the concentration of boric acid resulted in a significant increase in the prevalence of virus-induced mortality, although the mean time to death of larvae exposed to virus mixed with 0.5% boric acid did not significantly differ from that of larvae inoculated with AcMNPV and SpeiMNPV. The combination of AcMNPV with 1, 2 and 4% boric acid caused increases of 10, 40, and 53.4% in the mortality of third-instar T. ni larvae at 3 days after virus inoculation, respectively. The synergistic effect of boric acid on AcMNPV also acted on SpeiMNPV. The combination of SpeiMNPV with 1, 2, and 4% boric acid caused increases of 10, 30, and 50% mortality of S. exigua third-instar larvae at 4 days after virus inoculation, respectively. Thus, boric acid significantly enhanced the insecticide activity of AcMNPV and SpeiMNPV and acted as an effective viral synergist.
摘要 本實驗探討加州苜蓿夜蛾核多角體病毒 (Autographa californica multiple nucleopolyhedrovirus; AcMNPV) 和甜菜夜蛾核多角體病毒(Spodoptera exigua multiple nucleopolyhedrovirus; Spei MNPV) 分別添加硼酸 (boric acid) 後，對擬尺蠖 (Trichoplusia ni) 與甜菜夜蛾 (Spodoptera exigua Hubne) 幼蟲致病力之影響。結果顯示以1 × 108 polyhedral inclusion bodies (PIBs)/ml 之AcMNPV加入2% 硼酸一同感染三齡擬尺蠖幼蟲後，其半致死時間 (half-lethal time; LT50) 由4.1天縮短為3天。另外，以1 × 108 PIBs/ml 之SpeiMNPV加入2% 硼酸一同感染三齡甜菜夜蛾幼蟲後，其LT50由6.2天縮短為5.3天。雖然，0.5% 硼酸分別與1 × 108 PIBs/ml 的AcMNPV和SpeiMNPV混合，其對應之三齡甜菜夜蛾和擬尺蠖幼蟲之死亡率均未有顯著之影響，但1×108 PIBs/ml的AcMNPV與1, 2, 4% 硼酸混合後感染三齡擬尺蠖幼蟲，依1, 2, 4% 不同之硼酸濃度，三天後則分別增加了10, 40, 53.4% 的死亡率。此外，1×108 PIBs/ml的 SpeiMNPV與1, 2, 4% 硼酸混合後，感染三齡甜菜夜蛾，四天後死亡率分別比對照組增加了10, 30, 50%。綜合上述之結果，本研究證實硼酸可有效的增強AcMNPV及SpeiMNPV對擬尺蠖幼蟲和甜菜夜蛾幼蟲的致死率並縮短半致死時間，可以作為桿狀病毒生物農藥的協力劑。
| Key words: nucleopolyhedrovirus, Trichoplusia ni, Spodoptera exigua, boric acid, viral synergist | | 關鍵詞: 核多角體病毒、擬尺蠖、甜菜夜蛾、硼酸、病毒協力劑 |
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