青蔥甜菜夜蛾是宜蘭地區近年來最嚴重的青蔥害蟲,因為該蟲的幼蟲,均在蔥管內咀食蔥葉,一般農藥的噴射防治效果不彰,且可逃避天敵的侵襲,因此該蟲有逐漸嚴重的趨勢。本場為探討防治青蔥甜菜夜蛾有效途徑,曾收集殺蟲劑加以篩選試驗,雖有少數藥劑效果相當良好,但亦未能達徹底滿意的效益,故本研究以蟲生真菌(黑殭菌)之生物防治方法,以達到更佳防治效果。自78年10月至79年10月本場蘭陽分場以黑殭菌防治青蔥甜菜夜蛾,試驗採用逢機完全區集設計、九處理、三重覆,每處理之青蔥均噴射10濃度之黑殭菌胞子稀釋液,而將其處理黑殭菌胞子之青蔥,每隔0、1、2、3、4、5、6、7天之不同日數,分別採取青蔥飼養甜菜夜蛾幼蟲,然後每天調查其死亡率,以累計方法共調查10天。試驗結果以每隔0天及1天噴施黑殭菌之青蔥飼養之幼蟲,其死亡率最高,第一次試驗為73.3∼70.0%,第二次試驗為78.9∼73.3%,其次為每隔2天及3天之處理,其死亡率第一次試驗為66.7∼56.7%,第二次試驗為66.7∼61.6%,對照不噴施黑殭菌之死亡率最低,第一次試驗為1.7%,第二次試驗僅為1.1%。試驗結果顯示黑殭菌防治青蔥甜菜夜蛾效果良好。
The most serious insect pest on onion in I-Lan has been the beet armyworm Spodoptera exigua in recent years. Since the beet armyworm larva feed inside the green onion without eating throughout of the tube, they are well protected from any insecticide spray or natural enemies. For the past several years, many insecticides were tested in the field, and none of them had ever provided satisfactory control. However, Metarhizium anisopliae, a newly developed entomopathogenic fungi was found to be an effective control agent to the beet armyworm in our recent tests for green onion. To further test the effect of this agent, the field experiment was conducted and 9 treatments consists of spraying 10 spores of entomopathogenic fungi-Metarhizium anisopliae at intervals of 0, 1, 2, 3, 4, 5, 6, 7days and control were randomly arranged in 3 blocks. The green onion sprayed with entomopathogenic fungi in different interval days were each fed with beet armyworm in 10 succession days, and the accumulated death percentages of beet armyworm were counted daily until 10 days feeding. The results indicated that spraying of Metarhizium anisopliae in every day and 1-day interval gave73.3∼70.0 and 78.9∼73.3 death percentage in the first and second tests, respectivily. The death percentage of beet armyworm was only 1.1∼1.7 for control, indicating the Metarhizium anisopliae control beet armyworn effectively in green onion.