Dispersal Ecology of the Beet Armyworm in the Florida Panhandle: Implications for Outbreaks and Insecticide Resistance Spread

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This manuscript addresses seasonal occurrence and putative migratory origins of Spodoptera exigua in the Florida Panhandle using larval field surveys, pheromone trapping of adults, and hydrogen stable isotopes. The topic is timely and relevant to IPM in the southeastern USA. Below, I provide several issues that need attention before publication.

Major comments

1. The geographic origin of moths was assessed based on a small subset of samples (26 moths, 13 per side), which is insufficient to support several distinct patterns and may lead to a high degree of randomness in the assignment of geographic origins.
2. Keywords should be pared down and limited to terms supported by the results. For example, ‘southward movement’ should be removed or qualified, as only one sample indicates a possible southward migration.
3. Larvae of BAW appear only in July-August, while trap assays showed that adults were present earlier (Results: line 151-176 and Discussion: line 214-244). I suggest the authors link the effective accumulated temperature of BAW with June temperatures to evaluate the likelihood of a local generation.
4. For the method of pheromone traps, please provide details on composition and dose of the pheromone lure, manufacturer and loading, as well as the trapping protocol.
5. The current Results read as a continuous narrative, which makes it harder to map findings to key questions. Subheadings should be added to mirror the workflow.

 

Minor points

6. Line 170-176. The χ² result lacks degrees of freedom (df), model structure, and effort handling (Results: line 170-176).
7. The authors should standardize reference formatting throughout: unify capitalization, italicize Latin binomials with authorities in roman, and ensure complete bibliographic fields. For example:
   1: add page range.
   Ref. 5: Genus species (Authority); species in italics, authority in roman.
   Ref. 7: ‘Proceedings of the Beltwide Cotton Conference’ should use a lowercase ‘o’ in ‘Conference’.

Author Response

This manuscript addresses seasonal occurrence and putative migratory origins of Spodoptera exigua in the Florida Panhandle using larval field surveys, pheromone trapping of adults, and hydrogen stable isotopes. The topic is timely and relevant to IPM in the southeastern USA. Below, I provide several issues that need attention before publication.

Response #1: Thank you for your positive words and suggestions, which we have addressed below.

 

The geographic origin of moths was assessed based on a small subset of samples (26 moths, 13 per side), which is insufficient to support several distinct patterns and may lead to a high degree of randomness in the assignment of geographic origins.

Response #2: Thank you for your comment. In our study, approximately 75% of the samples exhibited a consistent pattern of probable origin, supporting robust conclusions about S. exigua migratory patterns. However, we acknowledge the relatively low number of samples as a limitation in the revised version of the manuscript (L. 275–276).

 

Keywords should be pared down and limited to terms supported by the results. For example, ‘southward movement’ should be removed or qualified, as only one sample indicates a possible southward migration.

Response #3: We changed to “insect pests”.

 

Larvae of BAW appear only in July-August, while trap assays showed that adults were present earlier (Results: line 151-176 and Discussion: line 214-244). I suggest the authors link the effective accumulated temperature of BAW with June temperatures to evaluate the likelihood of a local generation.

Response #4: June temperatures were within the optimal developmental range for BAW, with mean daily values of 25.6 °C (21.6-31 °C, min-max respectively), while the reported optimal range for larval development and survival lies between 27-35 °C. We added this information to this new version of the manuscript (L. 258-263).

 

For the method of pheromone traps, please provide details on composition and dose of the pheromone lure, manufacturer and loading, as well as the trapping protocol.

Response #5: We used bucket traps containing TRÉCÉ Pherocon beet armyworm (BAW) lures, GL/TR-3210-25. This information has been added to the new version of the manuscript (L. 104-108). Because of proprietary information, lure load rates and composition are not available.

 

The current Results read as a continuous narrative, which makes it harder to map findings to key questions. Subheadings should be added to mirror the workflow.

Response #6: We have added subheadings in the text and agree they help with the presentation of the results.

 

Line 170-176. The χ² result lacks degrees of freedom (df), model structure, and effort handling (Results: line 170-176).

Response #7: We now added the statistical analysis of these results in the methods and updated our Results section (L. 117-123, L. 195). Basically, we modelled the number of moths per trap per day as a function of the county, controlling the random effect of trap ID.

 

The authors should standardize reference formatting throughout: unify capitalization, italicize Latin binomials with authorities in roman, and ensure complete bibliographic fields. For example:

1: add page range.

Ref. 5: Genus species (Authority); species in italics, authority in roman.

Ref. 7: ‘Proceedings of the Beltwide Cotton Conference’ should use a lowercase ‘o’ in ‘Conference’.

Response #8: We have now updated our references. For Ref 5, this is a report and therefore the title of the report is in italic and what should be in italic (species name) is in roman. The automatic citation software Zotero changes the style of the references according to the journal guidelines.

Reviewer 2 Report

Comments and Suggestions for Authors

Good day, dear colleagues!

I have red your manuscript with a great interest. My only major remark regards to methods: how did you calculate the dispersal directions of BAW (Fig. 5)?

In addition, all the scale marks in Fig. 4d contains only zeros up to 4th sign after decimal point. Please, correct it.

Best wishes!

Author Response

Good day, dear colleagues! I have red your manuscript with a great interest. My only major remark regards to methods: how did you calculate the dispersal directions of BAW (Fig. 5)?

Response #9: Dispersal direction and distance were estimated using the wDist function from the assignR package. This approach uses the posterior probability surfaces generated for each sample to calculate the most likely origin areas. For each sample, the geographic distance and bearing between each potential origin pixel and the known collection site were computed and weighted by their posterior probabilities. This yields a weighted distribution of distances and directions that represents the probable dispersal pattern for each sample. We added more information on the new version of the manuscript (L. 163-169).

 

In addition, all the scale marks in Fig. 4d contains only zeros up to 4th sign after decimal point. Please, correct it.

Response #10: Figure 4 has been updated with the suggested changes.

 

Reviewer 3 Report

Comments and Suggestions for Authors

Review report

 

The manuscript addresses an important and timely topic concerning the migratory ecology of Spodoptera exigua (Beet Armyworm, BAW), a key agricultural pest with increasing resistance to insecticides. The integration of field sampling with stable isotope analysis provides valuable insight into the migratory origins and seasonal dynamics of this pest in the southeastern United States. The work has strong applied relevance for integrated pest management (IPM) and insect resistance management (IRM). The manuscript is generally well-written, logically structured, and the findings are clearly presented. However, there are some methodological issues that need to be addressed to strengthen the manuscript before acceptance.

 

Shortcomings in the Materials and Methods Section

 

1. The number of replicate fields per county and whether these represent independent replicates is unclear. Only four fields are listed—all appear to be in one county (Santa Rosa), but moth trapping occurred in two (Santa Rosa and Jackson). Clarify spatial replication and how sampling sites were selected (random, convenience, representative of regional cropping patterns, etc.).
2. The number of larvae collected or inspected per field/date is not specified. Without sample size information, it is impossible to assess sampling adequacy or population density.
3. The type of pheromone trap (bucket, delta, wing, universal, etc.) and pheromone lure composition and supplier are not described.
4. No information is given about trap height above ground, distance between traps, or trap maintenance schedule (lure replacement interval, sticky card changes, etc.).
5. The authors note that “trap inspections were conducted at varying intervals,” but do not specify how variable these intervals were or how standardization was applied.
6. The exact R packages or scripts used for isoscape calibration and assignment are not named (e.g., IsoMAP, assignR, isotopia). Reproducibility requires code or software details.
7. The calibration equation linking precipitation δ²H to tissue δ²H is not provided (slope, intercept, and r² values). Without these, the geographic inference cannot be evaluated.
8. The 5-arcminute resolution is mentioned, but it is unclear whether the isoscape encompassed North America only, or included Caribbean and Central American regions—which are referenced in the discussion. The geographic boundaries should be specified.
9. The methodology does not describe how assignment uncertainty or probability thresholds were handled (e.g., 50% or 95% confidence contours). This is standard in isotope-based origin models.
10. The phrase “average distance and direction of potential origins were calculated” needs methodological support. Was this done via vector averaging? Great-circle distance calculation? These details are missing.

Author Response

The manuscript addresses an important and timely topic concerning the migratory ecology of Spodoptera exigua (Beet Armyworm, BAW), a key agricultural pest with increasing resistance to insecticides. The integration of field sampling with stable isotope analysis provides valuable insight into the migratory origins and seasonal dynamics of this pest in the southeastern United States. The work has strong applied relevance for integrated pest management (IPM) and insect resistance management (IRM). The manuscript is generally well-written, logically structured, and the findings are clearly presented. However, there are some methodological issues that need to be addressed to strengthen the manuscript before acceptance.

Response #11: Thank you for your positive words and suggestions, which we have addressed below.

 

The number of replicate fields per county and whether these represent independent replicates is unclear. Only four fields are listed—all appear to be in one county (Santa Rosa), but moth trapping occurred in two (Santa Rosa and Jackson). Clarify spatial replication and how sampling sites were selected (random, convenience, representative of regional cropping patterns, etc.).

Response #12: Larvae were sampled from four peanut fields in Santa Rosa County only, selected to provide representative coverage of regional peanut production, with five sampling points per field spaced ≥ 20 m apart. Each field was treated as an independent replicate. This clarification has been added into the updated version of the manuscript (L. 94-103).

 

The number of larvae collected or inspected per field/date is not specified. Without sample size information, it is impossible to assess sampling adequacy or population density.

Response #13: To clarify sampling adequacy, we have now added the average number of larvae per field per species in the revised Results section (L. 181–183).

 

The type of pheromone trap (bucket, delta, wing, universal, etc.) and pheromone lure composition and supplier are not described.

Response #14: We used bucket traps containing TRÉCÉ Pherocon beet armyworm (BAW) lures, GL/TR-3210-25. Now added to the new version of the manuscript (L. 104-107). Because of proprietary information, lure load rates and composition are not available.

 

No information is given about trap height above ground, distance between traps, or trap maintenance schedule (lure replacement interval, sticky card changes, etc.).

Response #15: Bucket traps were installed 1.5 m above ground, spaced at least 100 m apart. Traps were checked one or two times per week, and lures were replaced every 4 weeks. This information has now been added to the Materials and Methods section (L. 104-108).

 

The authors note that “trap inspections were conducted at varying intervals,” but do not specify how variable these intervals were or how standardization was applied.

Response #16: Inspections were done one or two times per week. We added more information to the new version of the manuscript (L. 104-108, L. 115).

 

The exact R packages or scripts used for isoscape calibration and assignment are not named (e.g., IsoMAP, assignR, isotopia). Reproducibility requires code or software details.

Response #17: We used the assignR package. We added this information to the revised manuscript (L. 154).

 

The calibration equation linking precipitation δ²H to tissue δ²H is not provided (slope, intercept, and r² values). Without these, the geographic inference cannot be evaluated.

Response #18: The calibration equation and R² are: y = -56.14 + 0.61x, R² = 0.73. We now added this information to the revised manuscript (L. 161).

 

The 5-arcminute resolution is mentioned, but it is unclear whether the isoscape encompassed North America only, or included Caribbean and Central American regions—which are referenced in the discussion. The geographic boundaries should be specified.

Response #19: The isoscape used in our study encompassed a geographic area from 10°N to 50°N latitude and 130°W to 50°W longitude, covering North America as well as parts of the Caribbean and Central America. This information has been added to the Materials and Methods section in the revised manuscript (L. 155-158).

 

The methodology does not describe how assignment uncertainty or probability thresholds were handled (e.g., 50% or 95% confidence contours). This is standard in isotope-based origin models.

Response #20: Assignment uncertainty was addressed using posterior probability surfaces for each sample. The most likely origin areas were defined as the top 10% of grid cells with the highest posterior probability, corresponding to a 90% confidence interval for the sample’s origin. This has been clarified in the updated Materials and Methods section (L. 166-169).

 

The phrase “average distance and direction of potential origins were calculated” needs methodological support. Was this done via vector averaging? Great-circle distance calculation? These details are missing.

Response #21: Dispersal direction and distance were estimated using the wDist function, which calculates weighted distances and bearings between each sample’s collection site and potential origin locations based on posterior probability surfaces. This has been clarified in the revised Materials and Methods section (L. 163-166).

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The authors have provieded a generally revision in the latest version of the manuscript. I do not have additional major concerns.

Reviewer 3 Report

Comments and Suggestions for Authors

The authors have addressed all of my previous comments thoroughly and to my full satisfaction. The revisions have substantially improved the clarity, methodological transparency, and overall quality of the manuscript. I find that the concerns raised in the earlier review have been appropriately resolved, and I have no further remarks at this stage. The study now presents a coherent and well-supported contribution to the field.

I therefore recommend the manuscript for publication in its current form and would like to extend my sincere congratulations to the authors for their careful and constructive revisions.