Effects of High and Low Temperature Treatments on the Fatality of Eggs and Larvae of Melon Fly(Bactrocera cucurbitae, Diptera: Tephritidae) and the Analysis of Treated Muskmelon Quality

Abstract

本研究以40、42、44、46、48及50℃六種高溫及-2、0、2及4℃四種低溫處理，以及40~46℃高溫與-2~4℃低溫聯合處理，進行對採收後瓜實中瓜實蠅（Bactrocera cucurbitae（Coquillett））之殺蟲處理試驗，探討溫度對瓜實蠅卵、若齡幼蟲及三齡幼蟲死亡率之影響及其臨界死亡時間。先以各溫度處理於人工飼料中測試對卵、若齡幼蟲及三齡幼蟲之致死效果，以建立溫度-時間之處理模式，供作瓜實蠅殺蟲處理應用之基準。另於洋香瓜（Cucumis melo L. var. reticulatus Naud.）中進行各溫度對各蟲期之殺蟲試驗，作為各項處理對瓜類實際應用之範例與對照。各溫度處理之結果均以Probit分析其死亡率與處理時間之關係，連同估算之LT50、LT90、LT95及LT99均分別明列於文中各表中，各試驗結果之觀測值亦分別詳列於表中。以高溫40~50℃處理人工飼料中各蟲期達100 %死亡所需時間，以40、42及44℃處理下之三齡幼蟲需時1020、780及100分鐘為最長，而於46及48℃處理下則以若齡幼蟲需時55及15分鐘為最長，於50℃下處理各蟲期均於5分鐘內全數死亡。以高溫處理洋香瓜中各蟲期達100 %死亡所需之時間多較於人工飼料中者為長，而各溫度處理下均以三齡幼蟲需時最長。於-2~4℃四種低溫處理人工飼料中瓜實蠅時，各蟲期達100 %致死時間均以若齡幼蟲所需時間最長，於-2、0、2及4℃下分別需時144、144、144及192小時。以低溫處理洋香瓜中瓜實蠅時，各低溫下所需100 %致死時間均較於人工飼料中者為長，各低溫處理均以三齡幼蟲需時最長。以高溫40~46℃及低溫-2~4℃聯合處理，無論於人工飼料中及洋香瓜中，各蟲期達100 %致死時間多較單獨以高溫處理時所需致死時間為短，而於洋香瓜中需時又較於人工飼料中者為短。本研究亦以各項溫度處理下對處理後洋香瓜瓜實品質之影響，進行瓜實物理化學特性及感官品質之分析，結果顯示以高溫46℃處理45分鐘、低溫2℃處理168小時以及本研究所設定之各項高低溫聯合處理，所處理之瓜實均可維持不變之良好品質。

The effects of high temperature (i.e., 40, 42, 44, 46, 48 and 50℃) and low temperature (i.e., -2, 0, 2 and 4℃), as well as the high temperature (40 to 46℃) and low temperature (-2 to 4℃) combination, on the melon fly, Bactrocera cucurbitae (Coquillett), in post-harvested fruits were investigated in this study, and the effectiveness of various temperature treatments on the fatality of eggs, 1st and 2nd instars and the 3rd instars in fruits was evaluated. Eggs and larvae in artificial diet were used to establish the temperature-time models for killing the melon flies for the temperature regimes given above. Similar experiments were also done in muskmelon fruits (Cucumis melo L. var. reticulatus Naud.) to test the effectiveness of the chosen temperature treatments and compare the results with the models established in artificial diet. The relationships between the fatality of eggs and larvae and the temperature exposure time were analyzed, and the estimated LT50, LT90, LT95 and LT99 were calculated. For melon fly treated in the artificial diet, the lethal times of the most resistant stage required for 100% mortality were, respectively, 1020, 780 and 100 minutes for the 3rd instars at 40, 42 and 44℃, and 55 and 15 minutes for 1st and 2nd instars at 46 and 48℃. At 50℃, the melon fly at all stages were killed within 5 minutes. For each high temperature treatment, times required to kill the melon flies in muskmelon were longer than times required for flies in artificial diet, and the 3rd instars were the most resistant stage. The lethal times for the melon fly of the most resistant stage, i.e., 1st and 2nd instars, at low temperatures were, respectively, 144, 144, 144 and 192 hours at -2, 0, 2 and 4℃. The lethal times of low temperature treatments for melon fly in muskmelon were longer than in artificial diet, and the 3rd instars were the most resistant stage in all treatments. For the combined temperature treatments, the lethal times for the melon fly were shorter than those for the high temperature treatments; and those for fly in the muskmelon were shorter than in artificial diet. The quality of treated fruits was also analyzed in the present study by using fruit physicochmical analysis and the sensory evaluation. The results suggest the best temperatures for killing the melon fly in muskmelons without damaging fruit quality were high temperature of 46℃ for 45 minutes, low temperature of 2℃ for 168 hours as well as all of the high and low temperature combinations that designed in this study.