嘉義地區入侵紅火蟻（Solenopsis invicta）蟻巢之空間分布型與防治效果評估

Spatial Patterns of Ant Mounds and Evaluation of Control Efficacy for Red Imported Fire Ant in Chiayi

嘉義地區入侵紅火蟻（Solenopsis invicta Buren）於2003年10月被發現，2004年10月下旬才展開調查及防治工作。利用蟻巢密度的調查方法來評估防治成效，將發生嚴重區列為評估區，共計6個評估區，分別屬於水上鄉三界村與國姓村及中埔鄉金蘭村、隆興村、鹽館村、頂埔村等6個行政區。三界村及金蘭村評估區的調查初期，紅火蟻平均蟻巢數與其變異數之比值（s2/ x ）顯著大於1，表示入侵紅火蟻蟻巢的空間分布呈聚集型且符合負二項分布。此結果顯示紅火蟻蟻巢的分布極為集中，因此防治策略或許著重在特定重點區域去加強餌劑的施灑，應可以獲得很好的防治成效。結果顯示隨著防治次數的累加效果，蟻巢密度明顯減少，從2004年12月15日三界村的70個/樣區及金蘭村的84.7個/樣區，一年後分別降為2.9個及2.5個/樣區，其空間分布型也趨向於均勻化。2004-2008年歷經4年的積極防治，除金蘭村的防治率為96.26%外，其他5個評估區之防治率均達100%。2007及2009年全面普查後，再利用GIS估計發生面積分別約為65及20 ha，遠小於2006年的650 ha，顯示防治成效極為顯著，也顯示利用評估樣區進行防治成效評估之結果可推縯至嘉義地區全區之防治成效。

"Red imported fire ants (RIFA, Solenopsis invicta Buren) were first found in Chiayi in October of 2003, and survey and control efforts were begun at the end of October 2004. In order to evaluate the efficacy of red imported fire ant control, a sampling method was used to investigate mound density, with the more dense areas inside infested regions assigned as sampling plots for evaluating the efficacy. Six sampling plots were selected; the plots belonged to six administration districts, including Sanjie Village and Guosing Village of Shueishang Township, as well as Jinlan Village, Longsing Village, Dingpu Village, and Yanguang Village of Jhongpu Township. In the early period of the RIFA survey at Sanjie Village and Jinlan Village, the variance-mean ratio was significantly larger than 1, which meant that the spatial pattern of the RIFA mounds showed clustering and fit a negative binomial distribution. These results indicated that the distribution of RIFA mounds is extremely concentrated; hence, a control strategy focusing on several key infested regions to enhance bait application might be able to obtain good control efficacy. RIFA mound density was significantly decreased due to the cumulative effects of frequent bait application. The number of RIFA mounds was 70 mounds/plot at Sanjie Village and 84.5 mounds/plot at Jinlan Village on December 15th, 2004. One year later, the number of RIFA mounds at the two villages had dropped to 2.9 and 2.5/plot, respectively, and the spatial pattern of the mounds also tended toward a regular distribution. After active control efforts over four years from 2004 to 2008, the control rate for five of the sampling plots reached 100%, while that of Jinlan Village was 96.26%. The results of surveys for all the infested regions in 2007 and 2009 showed that the total area of RIFA infestation was estimated by GIS to be about 65 ha in 2007 and 20 ha in 2009, which was far smaller than the 650 ha estimated in 2006. The above results indicate that the performance of RIFA control efforts in Chiayi has been remarkable, and they also demonstrate that the efficacy of RIFA control in the sampling plots evaluated could be generalized to the control efficacy for all the infested regions in Chiayi."