進口糙米倉庫之米象及玉米象 (鞘翅目：椰象鼻蟲科) 對磷化氫之感受性調查

Abstract

Sitophilus oryzae and Sitophilus zeamais are the most common insect pests in imported brown rice warehouses in Taiwan. Brown rice severely infested by these weevil species results in huge grain losses. Since 2019, the Agriculture and Food Agency, with assistance from the Agricultural Research Institute, has assessed the effectiveness of fumigation in protecting imported brown rice from pests. From 2020 onward, the fumigation times and failure rates increased, with the detection of a high number of live insects in the stored brown rice. Therefore, we speculated that the pests in stored brown rice may have developed resistance to phosphine. Because S. oryzae and S. zeamais are the most common insect pests in imported brown rice, we collected live adults of these species from the imported brown rice warehouses, kept them in a laboratory with oatmeal fed to them, and assessed their susceptibility to phosphine to evaluate their phosphine resistance development. The results revealed that some S. oryzae strains from the warehouses developed medium-to-high degrees of resistance to phosphine. The strains from the Hukou Township, Ershui Township, Huatan Township, and Xihu Township warehouses developed moderate phosphine resistance, with a 15- to 36-fold resistance ratio. The phosphine resistance ratio in the Houbi District strain was as high as 50-fold. By contrast, the S. zeamais strains did not develop such high phosphine resistance, with the highest resistant ratios being only 5- to 6-fold in the Longtian Village and Annan Township strains. Considering the phosphine resistance in S. oryzae, we will evaluate the effectiveness of phosphine combined with various gases in the control of these pests in the future. 米象 (Sitophilus oryzae) 及玉米象 (Sitophilus zeamais) 為我國進口糙米倉庫中常見的主要害蟲，糙米在貯藏期若害蟲嚴重發生，常導致穀物巨量損失。目前進口糙米儲藏期間之積穀害蟲發生主要以磷化氫 (phosphine) 燻蒸進行化學防治，農業試驗所自 108 年起協助農糧署進行進口糙米燻蒸效果評估，但自 110 年起發現進口糙米燻蒸次數、燻蒸失敗率、燻蒸後糙米經 40 天後再檢查出活蟲比率有上升的趨勢，因此推測積穀害蟲可能已經產生磷化氫抗藥性。本研究於各進口糙米倉庫採集米象及玉米象活成蟲，帶回實驗室以麥片飼養後，進行磷化氫感受性試驗，了解現行各地進口糙米倉庫中之米象及玉米象對磷化氫之感受性，以及抗藥性的發生情形。試驗結果顯示，部分進口糙米倉庫中米象品系對磷化氫已產生中高程度抗藥性，其中新竹湖口、彰化二水、彰化花壇、彰化溪湖品系已發展出 15~36 倍的中度抗藥性，台南後壁品系之磷化氫抗藥性倍率更高達 50 倍；而玉米象則只發展出低程度的磷化氫抗藥性品系，最具抗性之台南隆田及台南安南品系僅只有 5~6倍。為解決米象對磷化氫的抗藥性問題，未來將探討以磷化氫搭配各式氣體，提升磷化氫的防治效果，克服抗性品系造成磷化氫燻蒸效果下降之問題。