Eradication and Control Strategies for Red Imported Fire Ants (Solenopsis invicta) in Taiwan

Round 1

Reviewer 1 Report

Numerous edits and comments are embedded in the manuscript. Many of the comments are in the pop-up comments linked to highlighted text. These comments and edits should be addressed.

The review article provides some interesting information, not readily available in published literature on spot eradications of red imported fire ants (RIFA) in Taiwan. However, results sections 3.1-3.2 were difficult to follow and were lacking purpose or discussion of how eradication policies or guidelines led to sustained reductions (or lack of reductions) of RIFA populations. Authors seem to be restating general guidelines and policies, but there was no indication of how well they were implemented.

The most useful information were the case studies, where they provided some insights on how localized populations of RIFA were eradicated. It would be even more informative to include more details on the frequency and types (formulations and active ingredients) of treatments that were applied (including unique treatment application techniques or strategies). Some of the eradications required several years, and the reasons for this should be discussed. Perhaps some treatments were ineffective? Documenting ineffective treatment protocols would be useful. Successful eradication treatments should be compared with successful treatments used for RIFA and other invasive ants in Australia and elsewhere. Are there common concepts that can be drawn from these eradication programs across countries?

Manuscript indicated what was implemented, but without a time frame relative to the first discovery of RIFA in specific areas, initiation of eradication programs, and progress toward eradication. Describing the level of the initial infestations (RIFA nest density per area) would give provide valuable information of the severity of the infestation before eradication programs were implemented. A figure with a timeline of these events comparing each of the case studies would provide a historical context of the eradication programs among the case studies. Tables 3-5 provide some of this data, however more details such as number of hectares infested by RIFA should be included in tables.

The overall status of RIFA in Taiwan should be discussed. Is RIFA eradicated from Taiwan? If not, how extensive are the remaining infestations? Is there a formal program to keep the RIFA-eradicated areas from being re-infested? Achieving localized RIFA eradications is commendable; is there a plan to expand RIFA eradication efforts for all of Taiwan? Discussing these questions may further validate the lessons learned from the localized eradications.

Comments for author File: Comments.pdf

Author Response

Dear Reviewers 1

Thank you for the opportunity to revise and resubmit our manuscript for consideration for publication in Sustainability.  The comments are helpful for making revisions. We have carefully considered each suggestion and revised the manuscript accordingly. Below, I list the details of those changes. Again, I appreciate your kind attention and effort in helping us improve the manuscript.

Responses to Reviewers’ comments:

Numerous edits and comments are embedded in the manuscript. Many of the comments are in the pop-up comments linked to highlighted text. These comments and edits should be addressed. The review article provides some interesting information, not readily available in published literature on spot eradication of red imported fire ants (RIFA) in Taiwan. However, results sections 3.1-3.2 were difficult to follow and were lacking purpose or discussion of how eradication policies or guidelines led to sustained reductions (or lack of reductions) of RIFA populations. Authors seem to be restating general guidelines and policies, but there was no indication of how well they were implemented.

Responses: Thank you very much for your thorough and constructive comments. We replied and addressed all the commented inserted in the manuscripts and believe that they have made the manuscripts improved for publication. For section 3.1 and 3.2, we included additional information to explain how eradication policies can sustain reduction of RIFA populations. Given the space issue, we focused on the implementation of those policies in our three cases. We used track-change in our revised manuscript to address your comments throughout the manuscript.

The most useful information were the case studies, where they provided some insights on how localized populations of RIFA were eradicated. It would be even more informative to include more details on the frequency and types (formulations and active ingredients) of treatments that were applied (including unique treatment application techniques or strategies). Some of the eradications required several years, and the reasons for this should be discussed. Perhaps some treatments were ineffective? Documenting ineffective treatment protocols would be useful. Successful eradication treatments should be compared with successful treatments used for RIFA and other invasive ants in Australia and elsewhere. Are there common concepts that can be drawn from these eradication programs across countries?

Responses: Thank you for your insightful comments. We now added more details on the frequency and types of treatments that were applied in our three cases.

It is true that some of the eradications required several years and we added discussions for three key reasons in Taiwan in conclusion section (Please see P19).

Manuscript indicated what was implemented, but without a time frame relative to the first discovery of RIFA in specific areas, initiation of eradication programs, and progress toward eradication. Describing the level of the initial infestations (RIFA nest density per area) would give provide valuable information of the severity of the infestation before eradication programs were implemented. A figure with a timeline of these events comparing each of the case studies would provide a historical context of the eradication programs among the case studies. Tables 3-5 provide some of this data, however more details such as number of hectares infested by RIFA should be included in tables.

Responses: Thank you for pointing this out and the suggestion is very helpful. We have now added a table with a timeline of these events in comparing to each of the case studies. We also added number of hectares infested by RIFA in three studied cases.

The overall status of RIFA in Taiwan should be discussed. Is RIFA eradicated from Taiwan? If not, how extensive are the remaining infestations? Is there a formal program to keep the RIFA-eradicated areas from being re-infested? Achieving localized RIFA eradications is commendable; is there a plan to expand RIFA eradication efforts for all of Taiwan? Discussing these questions may further validate the lessons learned from the localized eradications.

Responses: Thank you for the suggestions. We added the overall status of RIFA in Taiwan in the conclusions.  

Once again, thank you for your effort and time for reviewing our manuscript. 

Reviewer 2 Report

The authors propose a literature review on eradication efforts for the red imported fire ant and they focus on Taiwan. However, it became apparent that the work was not focused solely on eradication, but rather on mitigation efforts for the ant in three locations in Taiwan.  I would suggest de-emphasizing the eradication angle and focus the work on control efforts and the result for each case study. The title is misleading, and I would suggest changing it to something like, “Attempts at local control efforts for the red imported fire ant in Taiwan: Lessons from three case studies.” In every case study presented, the ants re-infested the area, so eradication was never sustained. The work is fairly well written, but verbose, and could be condensed considerably.

Author Response

Dear Reviewers 2

Thank you for the opportunity to revise and resubmit our manuscript for consideration for publication in Sustainability.  The comments were helpful for making revisions. We have carefully considered each suggestion and revised the manuscript accordingly. Below, I list the details of those changes. Again, I appreciate your kind attention and effort in helping us improve the manuscript.

Responses to Reviewers’ comments:

The authors propose a literature review on eradication efforts for the red imported fire ant and they focus on Taiwan. However, it became apparent that the work was not focused solely on eradication, but rather on mitigation efforts for the ant in three locations in Taiwan.  I would suggest de-emphasizing the eradication angle and focus the work on control efforts and the result for each case study. The title is misleading, and I would suggest changing it to something like, “Attempts at local control efforts for the red imported fire ant in Taiwan: Lessons from three case studies.” In every case study presented, the ants re-infested the area, so eradication was never sustained. The work is fairly well written, but verbose, and could be condensed considerably.

Responses:

Thank you for your constructive comments and suggestions. We now changed our title to "Eradication and Control Strategies of Red Imported Fire Ants (Solenopsis invicta) in Taiwan: Lessons from three case studies". Meanwhile, we will include eradication because all three selected cases have completed eradication process according to the policy guidelines. To clarify our text, we change the term “re-occurrence” to “re-invasion.” The term “re-occurrence” was misleading. Re-invasions took place in Yilan and Taichung due to movements of new plantation into the regions. Reported RIFA invasions and identified infested areas in the cases were eradicated according to a strict guideline. However, there are new invasions due to nursery and plantation transportation from outside the cities. We have chosen those cases to demonstrate the challenges of RIFA eradication. (Please see a brief discussion in the conclusions).

Once again, thank you for your effort and time for reviewing our manuscript. 

Reviewer 3 Report

I have read the manuscript by Helen K. Liu and colleagues, submitted to ‘Sustainability’. The manuscript describes eradication strategies of red imported fire ants, based on information from Taiwan. As invasive alien species, e.g. the fire ants, are real problem of the modern world, such data are valuable, and could be interesting for wider audience. Described by the Authors ‘lessons’ could be helpful for other countries.

The paper is based mostly on literature data. I found the manuscript interesting. I think, the data presented in the manuscript are worth to be published. Generally, the manuscript is well prepared, but I feel that the manuscript could be improved.

General comments
This paper concerns on the red imported fire ant, but I have found no information about the species, e.g., on origin of the species [it could be just two-three sentences, or a short paragraph, with such information, e.g. in the Materials and Methods section or Introduction section]. As the paper is mostly review (but see below), the information is necessary, and important for readers.

It is rather review/descriptive study, but the structure of the paper is similar to structure of original article (i.e., Introduction, Material and Methods, Results, Discussion). However, in the manuscript, there is section “3. Results”, but also section “4. Experience of Successful Eradication in Taiwan”. I am not sure, if I understand such structure of the manuscript.

Additionally, part of the information presented in the Result section, should be presented rather in Discussion, or Introduction (e.g., see lines 130-134).

Generally, I found difficult to follow some parts of the manuscript, as methods and results are scattered.

Descriptions of figures and tables could be improved, I think (several specific remarks are below). 

Some specific comments

There is no scientific name of the ant in the title, abstract, neither in the key words ­– the name of genus should be added, I think.

lines 50-52: “...experiences and lessons learned have come from the US and Australia…” – I think that a short information about the lessons could be useful for readers.

lines 66-67: “This area is unique because it includes a variety of land types”. – Please forgive me for my possible misunderstanding, but I believe that “a variety of land types” is present in many countries.

line 74: “Solenopsis invicta” – why not just “Solenopsis” (see: lines 30-31: “a new wave of IAS, the red imported fire ant (RIFA), a generic name for a eusocial insect from the genus Solenopsis”)

line 113: “Figure 2 shows the locations of the three eradication cases” – on the map there are showed districts, no locations.

Lines 201-202: “The governments or private agencies of RIFA-infected areas are responsible for the control and surveillance of RIFA according to standard protocols.” But what about costs of such actions (if private agencies are responsible)?

Figure 1. It is no very clear for me, e.g.:
- the red dots: on the legend dot is much bigger, than just on map – it could be confusing for readers,
- why there is no biosecurity zone in east-south direction?
- “The pink region illustrates the epicenter of RIFA incursion”, but description of the biosecurity zones are on the pink background – it could be confusing for readers.

Figure2. the description is very short. In scientific papers, captions of figures and tables should be self-explaining, i.e., should provide sufficient information to the readers without looking for information in the text. I think, that the description should be improved.
It is true also, e.g., for Table 2., Table 3., Table 4.

Figure 3. I have problem to understand the locality – e.g., is it center of the city presented on the photo?

Figure 4a. It is rather view of the ant species mound, no location(?)

Table 6. I am not sure if I understand the table. I think that better description (in the caption or just in the text, cf. lines 371 and next) could be useful for reader.

Generally, I think that Authors gathered interesting information, which are worth to be published. Nevertheless, I think that the figures and tables could be improved, and parts of the text could be arranged in a better way.

Author Response

Dear Reviewers 3

Thank you for the opportunity to revise our manuscript for consideration for publication in Sustainability.  The comments were helpful for making revisions. We have carefully considered each suggestion and revised the manuscript accordingly. Below, I list the details of those changes. Again, we appreciate your kind attention and effort in helping us improve the manuscript.

Responses to Reviewers’ comments:

I have read the manuscript by Helen K. Liu and colleagues, submitted to ‘Sustainability’. The manuscript describes eradication strategies of red imported fire ants, based on information from Taiwan. As invasive alien species, e.g. the fire ants, are real problem of the modern world, such data are valuable, and could be interesting for wider audience. Described by the Authors ‘lessons’ could be helpful for other countries.

The paper is based mostly on literature data. I found the manuscript interesting. I think, the data presented in the manuscript are worth to be published. Generally, the manuscript is well prepared, but I feel that the manuscript could be improved.

Responses: thank you for the constructive comments, which make the manuscript improved tremendously.

General comments

This paper concerns on the red imported fire ant, but I have found no information about the species, e.g., on origin of the species [it could be just two-three sentences, or a short paragraph, with such information, e.g. in the Materials and Methods section or Introduction section]. As the paper is mostly review (but see below), the information is necessary, and important for readers.

Responses: Thank you for pointing this out. We now added a brief description of RIFA in the introduction. (Please see P1).  

It is rather review/descriptive study, but the structure of the paper is similar to structure of original article (i.e., Introduction, Material and Methods, Results, Discussion). However, in the manuscript, there is section “3. Results”, but also section “4. Experience of Successful Eradication in Taiwan”. I am not sure, if I understand such structure of the manuscript.

Responses: Thank you for pointing this out. We reported our results in two sections in order to avoid having a long section. Section 3 reports results from literature review while Section 4 reports results from governmental records and reports of the eradication processes.

Additionally, part of the information presented in the Result section, should be presented rather in Discussion, or Introduction (e.g., see lines 130-134).

Generally, I found difficult to follow some parts of the manuscript, as methods and results are scattered.

Responses: Thank you for pointing this out. We made some revisions to shorten our result section. Additionally, we discussed information reported from lines 130-134 further throughout the discussion section when comparing eradication processes from Taiwan to the international experiences.

Descriptions of figures and tables could be improved, I think (several specific remarks are below).

Responses: Thank you for the detail comments and we made revisions accordingly. They are very helpful.

Some specific comments

There is no scientific name of the ant in the title, abstract, neither in the key words ­– the name of genus should be added, I think.

Responses: Indeed, we now added Solenopsis invicta in the keywords and title.

lines 50-52: “...experiences and lessons learned have come from the US and Australia…” – I think that a short information about the lessons could be useful for readers.

Responses: Thank you for the comment. We included the followings: “lessons learned have come from the US and Australia [17,18] and are used as important biological control tools for environmental sustainability. For instance, instead of broadcast treatment with application using helicopters or aircraft, prevention teams in Taiwan can use hand-held devices or all-terrain vehicle (ATV) quad bikes for bait spraying because of the complex landscapes involved.” Most documented RIFA eradication have taken place in more homogenous landscapes and lower population density areas. In contrast, more recent invasions have taken place in areas with a high human population density and heterogeneous land uses, and, thus, additional examination of the eradication strategies is required.”

lines 66-67: “This area is unique because it includes a variety of land types”. – Please forgive me for my possible misunderstanding, but I believe that “a variety of land types” is present in many countries.

Responses: Indeed. We clarified further that we were making comparisons to the US and Australia with RIFA infested areas. We included additional statements: “We chose Taiwan for our case study because there have been few in-depth publications on eradication in Taiwanese cities or counties since the first discovery of RIFA in Taiwan in 2003 [6,19]. In addition, this area is unique because it includes a variety of land use patterns when compared to the US or Australia, which have RIFA-infested areas. For instance, in Taiwan, the average farm area is 0.72 ha/ family, which is far less than in the US and Australia. Diverse land use types increase the difficulty of surveillance and bait spraying for RIFA.

line 74: “Solenopsis invicta” – why not just “Solenopsis” (see: lines 30-31: “a new wave of IAS, the red imported fire ant (RIFA), a generic name for a eusocial insect from the genus Solenopsis”)

Responses: Thank you for your questions. We revised the genus term for RIFA as Solenopsis invicta and make it consistent throughout the manuscript.

line 113: “Figure 2 shows the locations of the three eradication cases” – on the map there are showed districts, no locations.

Responses: Thank you for pointing this out. We included locations of RIFA sites/areas in Figure 2 to illustrate the relative positions of the discussed cases.

Lines 201-202: “The governments or private agencies of RIFA-infected areas are responsible for the control and surveillance of RIFA according to standard protocols.” But what about costs of such actions (if private agencies are responsible)?

Responses: Thank you for your questions. The costs are shared between the central governments and the local ones (as well as the private agencies). Often, the NRIFACC will provide treatments and training while the local governments (or private agencies) will supply personnel to implement the treatments. We added this in our text.      

Figure 1. It is no very clear for me, e.g.:

- the red dots: on the legend dot is much bigger, than just on map – it could be confusing for readers,

- why there is no biosecurity zone in east-south direction?

- “The pink region illustrates the epicenter of RIFA incursion”, but description of the biosecurity zones are on the pink background – it could be confusing for readers.

Responses: Thank you for your comments. I revised the description for Figure 1.  

Figure2. the description is very short. In scientific papers, captions of figures and tables should be self-explaining, i.e., should provide sufficient information to the readers without looking for information in the text. I think, that the description should be improved.

It is true also, e.g., for Table 2., Table 3., Table 4.

Responses: Thank you for your comments. The description for tables are revised and clarified.   

Figure 3. I have problem to understand the locality – e.g., is it center of the city presented on the photo?

Responses: Thank you for your question. We enlarged the photos and explained that those red marks in the photos indicate RIFA sites.    

Figure 4a. It is rather view of the ant species mound, no location(?)

Responses: Thank you for the comment. We added the location name to the discovered mound.  

Table 6. I am not sure if I understand the table. I think that better description (in the caption or just in the text, cf. lines 371 and next) could be useful for reader.

Responses: Thank you for pointing this out. We added description to Table 6.

Generally, I think that Authors gathered interesting information, which are worth to be published. Nevertheless, I think that the figures and tables could be improved, and parts of the text could be arranged in a better way.

Responses: Thank you for the constructive comments and we revised the figures and tables to better present information. Additionally, we also improved our structure to better organize the information. 

Once again, we really appreciate your time and effort in reviewing our manuscript.

Round 2

Reviewer 2 Report

All concerns addressed satisfactorily.

Author Response

Dear Reviewer,

Thank you for your effort and decision on our manuscript. We really appreciate your valuable time in reviewing our work. We attached the latest version for your reference. 

Sincerely,

Helen

Author Response File: Author Response.docx