植物油鉀鹽及植物精油對東方果實蠅產卵行為之影響

Abstract

東方果實蠅 [Bactrocera dorsalis (Hendel)] 為熱帶以及亞熱帶地區之重要害蟲，會因雌蠅的產卵行為造成果實的損傷，使果實失去經濟價值，其寄主植物包含 38 科超過 100 種經濟及非經濟作物，其中番石榴、柑橘、芒果及印度棗等皆為臺灣的重要經濟果樹。目前臺灣針對東方果實蠅的防治策略，主要是以降低田間族群數量為目的，而直接保護果實的套袋法，需耗費大量人力及成本，故須開發新型對環境較為友善且能直接對果實進行保護之防治策略。但新興之果實蠅防治潛力物質，如：礦物油、植物油、植物精油以及其他植物萃取物，多為親脂性物質，使用上皆需添加化學合成界面活性劑才得以利用，此與避免使用化學合成藥劑之初衷相互矛盾。 故本研究希望將植物油藉由皂化反應，製造為具有界面活性劑性質之植物油鉀鹽，並對 4 種植物油鉀鹽以及 15 種植物精油進行東方果實防治效果之選擇性及非選擇性試驗，觀察其防治效果及作用機制，同時探討植物油脂肪酸組成與植物油鉀鹽防治效果之關係。並自其中篩選防治效果較佳之植物油鉀鹽及植物精油混合施用，期望可增加其防治效果並了解可能之作用機制。 試驗結果顯示植物油鉀鹽的作用機制為阻礙東方果實蠅於番石榴上製造產卵孔，進而減少其產卵數量，在 4 種植物油鉀鹽中，以長鏈不飽和脂肪酸比例最多的葵花籽油鉀鹽防治效果最佳，在 1% 濃度下於選擇性試驗中可達到 57.1% 產卵孔減少指數；2% 濃度下於選擇性試驗中可達到 34.4 及 51.5% 產卵孔減少指數及產卵忌避指數，而在非選擇性試驗中則可達 61.0% 產卵孔減少指數，此結果表示若植物油中長鏈不飽和脂肪酸比例較高，則其防治效果較佳。在 15 種植物精油中以檸檬草精油效果較佳，具有東方果實蠅忌避效果，使其遠離人工產卵器進而降低其產卵數量，在 1 mL/L 濃度下於選擇性試驗中可顯著減少東方果實蠅於人工產卵器的停留次數以及產卵數量，達到 26.0 及 18.6% 忌避指數及產卵忌避指數。將葵花籽油鉀鹽及檸檬草精油混合施用後發現，葵花籽油鉀鹽在加入檸檬草精油後，其阻礙東方果實蠅製造產卵孔的能力會下降，但可因檸檬草精油之作用，達到減少產卵數量的效果，其中以 2% 葵花籽油鉀鹽混合 1 mL/L 檸檬草精油效果較佳，於選擇性試驗可達 51.5 及 62.5% 產卵孔減少指數及產卵忌避指數，於非選擇性試驗可達 48.0% 產卵忌避指數。故本研究結果顯示混合葵花籽油鉀鹽及檸檬草精油可有效提升對東方果實蠅之防治效果。

The oriental fruit fly, Bactrocera dorsalis (Hendel), is a very destructive insect pest and is widely distributed in tropical and sub-tropical regions of the world. Fruit are damaged by the oviposition behavior of the female fruit fly and lose its commercial value. B. dorsalis will infest over 100 species of host plants including economic and non-economic fruits. Of these host plants, guava, citrus, mango and jujube are important economic fruits in Taiwan. Most strategies in Taiwan are focused on reducing the number of B. dorsalis in the field, or using bags to protect fruit directly from fruit fly, which is an expensive and labor-intensive method. Thus, it is necessary to develop more environmentally safe methods which protect fruit directly. In previous studies, mineral oils, vegetable oils, essential oils and other extracts of plant were shown to have potential for controlling B. dorsalis. However, they are all hydrophobic materials, and the addition of synthetic surfactant is necessary for use. This is contradictory to the original intention of avoiding the use of synthetic compounds. The objective of this study was to saponify vegetable oils to make it into potassium salt of vegetable oils which have the characteristics of surfactant. And we evaluated the effect of 4 potassium salt of vegetable oils and 15 essential oils on oviposition behavior of B. dorsalis and their mechanism by using the choice and non-choice test. The relation between fatty acid composition of vegetable oils and the effect on oviposition behavior will also be investigated. And the potassium salt of vegetable oil and essential oil that exhibits the strongest effect were selected to determine the effect of a mixture of potassium salt of vegetable oil and essential oil on oviposition behavior. The result showed that potassium salt of vegetable oils prevented B. dorsalis from making oviposition punctures on guava, which reduced the number of eggs in guava. In four vegetable oils, potassium salt of sunflower seed oil contains the largest proportion of long-chain unsaturated fatty acid and showed the strongest effect. In choice test, 1% solution showed 57.1% of puncture deterrence index. And 2% solution reached 34.4 and 51.5% of puncture deterrence index and oviposition deterrence index in choice test respectively, and reduced the number of punctures by 61.0% in non-choice test. The results showed that as the proportion of long-chain unsaturated fatty acid in vegetable oils increased, the effect will also increase. In 15 essential oils, lemongrass essential oil showed the strongest repellent effect on B. dorsalis and significantly reduced not only cumulative landing of female fruit fly on the ovitraps, but also the number of eggs laid. At a concentration of 1 mL/L, it showed 26.0 and 18.6% of repellency index and oviposition deterrence index in choice test respectively. After mixing the potassium salt of sunflower seed oil and lemongrass essential oil, the effect of potassium salt of sunflower seed oil on preventing fruit fly from making oviposition punctures was reduced. On the other hand, because of the addition of lemongrass essential oil, the effect of reducing the number of eggs increased. The mixture of 2% potassium salt of sunflower seed oil and 1 mL/L lemongrass essential oil showed the strongest effect. The mixture reached 51.5 and 62.5% of puncture deterrence index and oviposition deterrence index in choice test respectively, and 48.0% of oviposition deterrence index in non-choice test. This study showed that mixing the potassium salt of sunflower seed oil and lemongrass essential oil will increase the effect on controlling B. dorsalis.