Biology and the optimal rearing conditions of a specialist larval parasitoid Psyttalia fletcheri in Zeugodacus cucurbitae

瓜實蠅（Zeugodacus cucurbitae (Coquillett)）在台灣為葫蘆科 （Cucurbitaceae）作物栽培期間的關鍵害蟲，在本研究對幼蟲期寄生蜂 Psyttalia fletcheri Silvestri 寄生行為的觀察中，發現其寄生產卵位置大多在瓜實蠅幼蟲腹部中段背方或側方，被寄生的幼蟲會呈現短暫類似麻痺無法活動的情形。逐日解剖被寄生瓜實蠅個體，觀察此寄生蜂各蟲期發育情形，換算此寄生蜂在23℃時從卵發育至蛹期約需 8.0 日，蛹體約經過 11.0 日後羽化為成蟲，且 P. fletcheri 寄生瓜實蠅初齡幼蟲僅少數成功羽化出子代寄生蜂。測試 P. fletcheri 在不同定溫環境下的生物表現，結果顯示 P. fletcheri 在 13、18、23、28、33℃ 等 5 種不同定溫環境下，只在 18、23、28℃ 具備成功寄生產出子代寄生蜂之能力，以 23℃ 下具有最高的繁殖潛能，每一雌寄生蜂一生平均可產 116.6 ± 16.5 隻後代，與其他二種溫度處理者呈顯著差異。在這三個定溫中，雌成蟲平均壽命在 18℃ 時最長，平均為 20.3 ± 8.9 日，雄成蟲壽命則在 18、23℃ 最長，分別為 18.1 ± 2.4、18.7 ± 9.5 日，顯著高於其他溫度，子代的發育時間則隨溫度增加而減短，由卵期至羽化雄蟲分別需要 34.3 ± 0.1、19.3 ± 0.1及 15.0 ± 0. 4 日，雌蟲則分別需要 36.0 ± 0.2、20.3 ± 0.1、15.8 ± 0.3日；且發現 P. fletcheri 在光照與無光照條件下均具有產卵寄生能力，平均每一雌寄生蜂於 1 - 18日齡間能產出子代數分別為 46.4 ± 6.5、34.5 ± 3.4 隻，兩者間無顯著差異。此外，測試成蟲期餵食龍眼蜜、果糖、楓糖、黑糖蜜等四種不同糖類對其寄生能力的表現，結果顯示不餵食的對照處理組，雌、雄寄生蜂平均分別能存活 3.8 ± 0.3、3.4 ± 0.1 日 ，且雌蟲無法產出後代，但僅供給 RO 水者雌、雄成蟲平均分別可存活 8.0 ± 0.3、7.2 ± 0.4 日，一隻雌蟲平均可產下 13.3 ± 1.2 隻後代，而餵食不同糖類食物處理中，每一雌寄生蜂試驗期間可產出子代數，以黑糖蜜處理組最多，平均為 48.9 ± 2.9 隻，其次分別為餵食楓糖、龍眼蜜、果糖，平均為 46.7 ± 1.8、45.0 ± 3.1、44.8 ± 3.2 隻後代，但四種餵食處理組彼此間無顯著差異；進一步分析餵食不同處理後的子代雌雄比，發現餵食黑糖蜜及果糖處理組最高，分別達 4.0 ± 0.2、3.6 ± 0.1，與其他處理組呈顯著差異。而在寄主專一性測試中，當分別供給 P. fletcheri 瓜實蠅、南瓜實蠅與東方果實蠅的幼蟲，平均一隻雌寄生蜂分別能產出 5.0 ± 0.1、1.9 ± 0.3、0.1 ± 0.1 隻子代寄生蜂，彼此間呈顯著差異。另外，本試驗探討此寄生蜂的寄主搜尋機制，P. fletcheri 對於新鮮瓜果、新鮮瓜果切片、受害瓜果切片產生寄主搜尋行為的反應率分別為 45.0 ± 5.0 %、30.0 ± 6.0 %、65.0 ± 8.0 %，當有瓜實蠅幼蟲存在時會有較多的雌成蟲有搜尋寄主的表現，且只對苦瓜、絲瓜、花胡瓜等瓜類有反應，而不會選擇番木瓜、番石榴兩種水果。最後，探討 P. fletcheri 與格氏突闊小蜂（Dirhinus giffardii Silvestri）間的交互作用，結果顯示單獨被 P. fletcheri 寄生的處理組平均可產出 17.3 ± 2.6 隻後代，單獨被格氏突闊小蜂寄生的處理組平均可產出 28.3 ± 7.1 隻後代，而先被 P. fletcheri 寄生的瓜實蠅幼蟲，化蛹後再經格氏突闊小蜂寄生的處理組，則分別可產出 10.5 ± 2.1 隻 P. fletcheri 後代及 29.3 ± 7.0 隻格氏突闊小蜂後代，羽化為瓜實蠅的數量則分別為 74.3 ± 3.1、61.3 ± 6.8、39.8 ± 8.8 隻，彼此間具有顯著差異，此初步結果顯示當兩種寄生蜂共同應用時，有助於提高瓜實蠅被寄生的效率，但格氏突闊小蜂可能會影響 P. fletcheri 的寄生表現。The melon fruit fly, Zeugodacus cucurbitae (Coquillett) (Diptera: Tephritidae) is a major pest of cucurbitaceous vegetables. In this study, we observed that a melon fly larval endoparasitoid, Psyttalia fletcheri (Silvestri) (Hymenoptera: Braconidae) usually sting the back or lateral side of the middle of larvae body, and caused larvae paralyzed for a few minutes. At 23°C, the life cycle of P. fletcheri need about 8 days from egg hatching to pupation, and adult emerged from the host pupae bout 11 days will. Nearly null P. fletcheri can parasitize first instar larvae successfully. P. fletcheri can survive and reproduce when held at 18, 23, and 28°C. The longest longevity for female was 20.3 ± 8.9 days at 18 °C, and male was 18.1 ± 2.4, 18.7 ± 9.5 days at 23, 18 °C, respectively. Significant difference was found among three tested temperatures for the mean total progeny produced. The highest number recorded was at 23 °C for 116.6 ± 16.5 per female. There was no significant difference of progeny sex ratio among three temperatures. Increasing temperature reduced the development time from 34.3 ± 0.1, 19.3 ± 0.1 to 15.0 ± 0. 4 days for male, and 36.0 ± 0.2, 20.3 ± 0.1, 15.8 ± 0.3 days for female at 18, 23 and 28 °C, respectively. And we also found that the total progeny of P. fletcheri among 1-18-day-old was not significantly different at light (46.4 ± 6.5) and dark (34.5 ± 3.4) period. Four sugar diets: molasses, fructose, honey and maple syrup were tested to determine the effect on reproduction of female P. fletcheri. The results showed that the type of sugar did not have significant effect in the number of progeny produced by female P. fletcheri. The mean total number of progeny per P. fletcheri female were 48.9 ± 2.9, 44.8 ± 3.2, 45.0 ± 3.1, 46.7 ± 1.8, respectively. However, significantly higher female progeny sex ratios were found when female was fed with molasses and fructose than honey and maple syrup. The ratios were 4.0 ± 0.2 and 3.6 ± 0.1 for molasses and fructose, respectively. In the control group P. fletcheri not provided food was not able to produce progeny, male and female lived 3.8 ± 0.3 and 3.4 ± 0.1 days, respectively. Those fed RO water only, male and female lived 7.2 ± 0.4, 8.0 ± 0.3 days. P. fletcheri successfully parasitized the larvae of melon fly and Zeugodacus tau, The number of progeny per P. fletcheri female were 5.0 ± 0.1 and 1.9 ± 0.3, respectively, but nearly null when parasitized the oriental fruit fly (Batrocera dorsalis)( 0.1 ± 0.1) . Further, the response rates of P. fletcheri making host searching behavior were 45.0 ± 5.0 %, 30.0 ± 6.0 %, 65.0 ± 8.0 % ,respectively, for fresh fruits, fresh fruits slices, and injured fruits slices. P. fletcheri only responded to bitter gourd, sponge gourd and cucumber. At last, the interaction between P. fletcheri and Dirhinus giffardii Silvestri was investigated.The mean number of emerged parasitoid of three treatment were 17.3 ± 2.6 which melon fly larvae just parasitized by P. fletcheri, 10.5 ± 2.1 P. fletcheri and 29.3 ± 7.0 D. giffardii which melon fly larvae parasitized byP. fletcheri first then gived to D. giffardii, and 28.3 ± 7.1 which melon fly pupae just parasitized by D. giffardii. This preliminary result showed that releases of P. fletcheri and D. giffardii together increased suppression of Z. cucurbitae. However, D. giffardii seemed to affect the parasitic performance of P. fletcheri.摘要 i Abstract iii 目次 v 表目次 viii 圖目次 ix 前言 1 前人研究 2 材料與方法 13 一、供試蟲源與繼代繁殖 13 1. 瓜實蠅 Z. cucurbitae 13 2. 幼蟲寄生蜂 P. fletcheri 14 3. 格氏突闊小蜂 D. giffardii 15 二、P. fletcheri 寄生行為觀察 15 三、測試不同定溫下 P. fletcheri 的壽命及對瓜實蠅幼蟲的寄生率 15 四、P. fletcheri 日夜寄生情形觀察 16 五、P. fletcheri 對不同齡期瓜實蠅幼蟲的寄生偏好性測試 16 六、P. fletcheri 成蟲餵食不同糖類對寄生率之影響 16 七、P. fletcheri 寄主專一性測試 17 八、P. fletcheri 寄主搜尋機制探討 18 1. 新鮮果偏好性選擇 18 2. 不同新鮮果實切片偏好性測試 18 3. 測試瓜實蠅幼蟲在不同瓜果的發育時間 18 4. 受害果實偏好性選擇 18 九、格氏突闊小蜂對瓜實蠅幼蟲已（或未）被 P. fletcheri 寄生的寄主選擇偏好 19 十、統計與分析 19 結果 20 一、P. fletcheri 寄生行為觀察 20 二、不同定溫下 P. fletcheri 的壽命及對瓜實蠅幼蟲的寄生情形 20 三、P. fletcheri 有無光照條件下之寄生情形 21 四、P. fletcheri 對不同齡期瓜實蠅幼蟲的寄生偏好 22 五、P. fletcheri 成蟲餵食不同糖類後之寄生率 22 六、P. fletcheri 寄主專一性測試 24 七、P. fletcheri 寄主搜尋機制探討 25 八、格氏突闊小蜂對幼蟲期已（或未）被 P. fletcheri 寄生的寄主選擇偏好 26 討論 27 一、P. fletcheri 的寄生行為 27 二、不同定溫下 P. fletcheri 對瓜實蠅幼蟲寄生率之比較 28 三、P. fletcheri 有無光照條件下之寄生情形觀察 30 四、P. fletcheri 對不同齡期瓜實蠅幼蟲的寄生偏好 30 五、餵食不同成分之成蟲飼料對 P. fletcheri 寄生率之影響 31 六、P. fletcheri 寄主專一性測試 32 七、P. fletcheri 寄主搜尋機制探討 33 八、寄生蜂間之種間競爭 34 結論 36 參考文獻 3