以入侵紅火蟻（膜翅目：蟻科）覓食習性為基礎研發其抗水性防治餌劑

Abstract

為評估具有抗水潛能的材料，用以製作火蟻餌劑載體（carrier），本試驗建立一套有效的火蟻生物檢定（bioassay）方法。於實驗室條件下，分別調查入侵紅火蟻（Solenopsis invicta Buren）工蟻密度、覓食區域大小、食物誘餌種與類數量及蟻后存在與否，對覓食活動率的影響。結果顯示，在600隻工蟻與120隻幼蟲、一次使用4種食物誘餌和放置2.5小時等條件下，進行火蟻食物偏好性研究最有效率；蟻后的存在會降低入侵紅火蟻覓食活動率。本試驗也調查了在不同活動表面上火蟻工蟻覓食活動率之影響，結果顯示工蟻覓食活動率於平滑塑膠表面比在土壤表面相對為高，，障礙物會降低火蟻覓食效率；另外，剛採自野外的入侵紅火蟻工蟻的覓食效率比已飼養在實驗室環境一年以上的火蟻高。於實驗室與野外條件下，分別評估市售餌劑微膠囊化之後，火蟻對其偏好以及抗水能力，結果觀察到微膠囊包覆的厚度與餌劑抗水能力成正比；利用5%的 poly-ε-caprolactone包覆後，比一般餌劑多出大約20%的抗水能力；然而，微膠囊包覆後餌劑和潮溼的餌劑，二者對火蟻的吸引力均低於一般正常狀態下之餌劑。另一方面，在實驗室條件下，進行入侵紅火蟻對酒糟（DDGS）構成的餌劑載體（T-載體）之偏好性。T-載體是由大豆油與蝦殼粉末（SSP）混和而成，並進行火蟻對T-載體之偏好性評估。結果顯示，T-載體含有15%的大豆油與20%的蝦殼粉末時，誘集到之火蟻數量高於其他混合比例。當T-載體沒有混和大豆油與蝦殼粉末時，對火蟻的誘集力明顯高於市售的商用載體（C-載體）。而當混合15%大豆油與20%蝦殼粉末的T-載體潮溼之後，對火蟻的誘集力比潮溼的商用載體高出大約10倍。利用T-載體與15%大豆油與20%的蝦殼粉末作為誘食劑（phagostimulants），加上 0.128% 的賽滅寧 (cypermethrin)製成T-餌劑，在實驗室條件下，正常狀態的T-餌劑以及C-餌劑 (0.045% 因得克) 在四天內，均能殺死全部的工蟻。但是潮溼狀態的T-餌劑和C-餌劑在四天內分別只殺死了70.62%和39.68%工蟻。在野外環境下，正常狀態的T-餌劑和C-餌劑幾乎有相同的效率。當T-餌劑與C-餌劑潮溼後，T-餌劑的殺蟻能力會下降，但C-餌劑幾乎完全喪失殺蟻能力。也可以混合其他種殺蟲劑，例如 d-亞列寧 (d-allethrin)、百滅寧 (permethrin) 和除蟲菊精 (pyrethrin)。T-載體也在實驗室與野外條件下，評估T-載體與白殭菌 (Beuveria bassiana) F256 混合的殺蟻能力。結果顯示，白殭菌的施用方式對火蟻的防治效果有顯著影響。直接將白殭菌施用在火蟻巢內，會比混合在餌劑中更有效率，處理完後28天，直接施用白殭菌與商用火蟻餌劑 Advion® (0.045% 因得克) 均能消滅90%的火蟻巢。 Advion® 和Esteem® (0.5%百利普芬) 在野外條件下，殺死火蟻的速度比直接施用白殭菌分別快出大約3倍和慢於3.5倍。總而言之，基於火蟻餌劑之抗水能力暴露野外的安定性在實驗室與野外條件下的殺蟻能力，以及與誘食劑、毒性物質和白殭菌 F256的結合能力，本試驗所研發之T-載體並據以製成之T-餌劑，在潮溼環境下，對火蟻具有很好防治效率。

An efficient bioassay for the screening of local materials to find a potential water -resistant fire ant bait carrier was developed. To develop an efficient bioassay, the effect of Solenopsis invicta Buren (red imported fire ant, RIFA) worker population size, size of the foraging area, the number of foods, duration of experiments and the effect of the queen’s presence on foraging activity of RIFA workers were investigated under laboratory conditions. The results showed that 600 workers with 120 broods was the most efficient combination for the RIFA workers preference study. The foraging activities of RIFA were significantly decreased by the presence of queen in the nest. The optimal duration for RIFA preference study was 2.5 h with 4 foods placement. The effects of different ground surfaces on the foraging efficiency of RIFA workers were also investigated. The RIFA workers were more efficient when they foraged on hard and smooth plastic surfaces than on soil surfaces. Similarly, obstacles reduced the foraging efficiency of RIFA workers. The RIFA workers from wild colonies were more efficient than the workers from one-year-old laboratory colonies. A commercial fire ant bait (Esteem®, 0.5% pyriproxyfen) was microencapsulated and evaluated under both laboratory and field conditions for the RIFA’s preference and water resistance abilities. A positive correlation between microencapsulation rate and water resistance ability of bait was observed; a bait coated with 5% poly-ε-caprolactone was more resistant to water by ~20% than normal bait. However, the microencapsulated and wet baits were less preferred than normal baits by the RIFA workers. In another study, preference of RIFA for distiller's dried grains with solubles (DDGS) was investigated under the laboratory conditions. The DDGS was mixed with soybean oil and shrimp shell powder (SSP), and then evaluated. The DDGS only attracted significantly larger number of RIFA workers than the commercial bait (Advion, 0.045% indoxacarb) (C-bait). The DDGS containing 15% oil and 20% SSP attracted largest number of RIFA workers than rests of combinations. The wetted DDGS with 15% oil and 20% SSP attracted ~10 times more RIFA workers than the wetted C-bait. Accordingly, a new fire ant bait (T-bait) was prepared by using DDGS with 15% soybean oil and 20% SSP as phagostimulants, and cypermethrin (0.128%) as toxicant. The 100% RIFA workers were killed within 4 days by a normal T-bait (cypermethrin 0.128%) or C-bait (Advion®, indoxacarb 0.045%) in the laboratory; however wetted T-bait or wetted C-bait killed only 70.62% and 39.68%, respectively. Similarly, efficacy of T-bait was also higher than the C-bait against RIFA workers when exposed to the field. However, under field conditions, normal T-bait and normal C-bait had almost the same efficacy. And, when T-bait and C-bait were wetted, efficacy of T-bait to inactivate RIFA mounds was somewhat reduced, while C-bait lost most of its efficacy to inactivate RIFA mounds in the field. DDGS was compatible with other insecticides, such as d-allethrin, permethrin and pyrethrin. The DDGS was also mixed with Beuveria bassiana F256, a native strain, and was evaluated the effect on the killing of RIFA under the laboratory and field conditions. The B. bassiana delivery methods had significant effects on the mortality of RIFA. The direct application of B. bassiana into the mound had higher efficacy to inactivate RIFA mounds than its bait application. Twenty eight days after treatment, the direct application of B. bassiana and Advion® (indoxacarb 0.045%) inactivated ~90% of RIFA mounds in the field. The Advion® and Esteem® (0.5% pyriproxyfen) inactivated RIFA mounds ~3 times faster and ~3.5 times slower than the direct application of B. bassiana in the field conditions, respectively. Based on its abilities to resist water and field exposure, its RIFA killing capability under both laboratory and field condition, as well as its compatibility with phagostimulants, toxicants and B. bassiana F256, we conclude that DDGS based fire ant bait (T-bait) is an efficient fire ant bait suitable for humid conditions.