Silicon as a Tool to Manage Diaphorina citri and Relation Soil and Leaf Chemistry in Tahiti Lime

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

General Comments

This study evaluated two sources of silicon—diatomaceous earth (organic) and soluble silicate (inorganic)—applied either to leaves, soil, or both, in a Tahiti lime orchard in Colombia. Results showed that diatomaceous earth, applied foliarly or in combination, reduced new shoot growth and lowered psyllid incidence during the first 30 days. Although silicon did not reduce egg-laying, it appeared to interfere with the development of psyllids from nymph to adult. Silicon also improved soil health by increasing pH, organic matter, and nutrient availability, while raising nutrient levels in leaves, including nitrogen, phosphorus, potassium, and iron. All treatments led to greater silicon accumulation in leaves. In addition, fruit quality improved, with treated trees producing heavier fruit and more juice than the control.

The experiment was well replicated and included an appropriate control. The results are interesting and address an important global pest of citrus. However, the study has limitations. It was conducted in only one season, at a single location, where Asian citrus psyllid populations were very low. This makes it difficult to extrapolate how silicon treatments might perform under higher psyllid densities, which are more typical in regions severely affected by this pest and huanglongbing. In addition, no effort was made to test whether silicon influenced transmission of the pathogen itself, an essential component of disease management. Such data would have required a longer (likely two-year) study and could have yielded more definitive results.

Nonetheless, the improvement in yield after just one year of treatment is noteworthy. My main recommendation is that the authors clearly acknowledge the limitations of their work: the lack of replication across time and space, the unusually low psyllid populations, and the absence of pathogen transmission data. Without this caution, the study risks overstating the potential of silicon as a control tool against this serious pest.

Specific Comments

• Line 128: Spell out “analysis of variance” at first use.
• Figure 1: Panels A, B, and C should be labeled. The X-axis label in panel B should be translated into English.
• Section 3.1: Psyllid populations in this one-year trial were extremely low. The negative control averaged only about 0.5 psyllids per flush. In regions such as Florida, Mexico, and China, psyllid populations are typically much higher—even under heavy insecticide use. Results observed here may not hold under such higher densities. The authors should emphasize this limitation, particularly since the study was not replicated across years or locations. Generally, such trials should be conducted over at least two years or in multiple locations before recommendations can be made. I strongly advise against making broad claims about the usefulness of silicon against ACP based on one year of data from a site with unusually low populations. Importantly, no data were collected on whether silicon treatments affect transmission of the HLB pathogen. This remains a critical unanswered question.
• Figure 3: Both X and Y axis labels are missing and should be provided.
• Lines 284–287: The current sentence suggests that the study measured oviposition, nymph weight, or feeding rates, which it did not. This should be re-written to avoid that implication.
• Lines 320–340: This section consists of many short, individual statements. These should be consolidated into more cohesive, integrated paragraphs.

Author Response

Reviewer 1

General comment: … My main recommendation is that the authors clearly acknowledge the limitations of their work: the lack of replication across time and space, the unusually low psyllid populations, and the absence of pathogen transmission data. Without this caution, the study risks overstating the potential of silicon as a control tool against this serious pest.

 

Answer: As highlighted in the discussion (Pages 12, lines 388–396), Colombia’s tropical climate promotes frequent vegetative flushing, which can favor the proliferation of the insect vector. Nonetheless, the integrated phytosanitary management practices established under Resolution 1668 of 2019 (ICA, 2019)—including systematic monitoring, deployment of yellow sticky traps, nutritional optimization, application of biological control agents, regulation of host plants, and, when necessary, chemical control—have contributed to maintaining low vector incidence in citrus plantations within the evaluated region. In line with these observations, it is recommended that future studies encompass at least two consecutive productive years and be conducted in regions with high pest pressure and confirmed presence of Huanglongbing, to enable a more robust assessment of epidemiological patterns and the efficacy of control strategies under adverse conditions.

 

Specific Comments:

1. Line 128: Spell out “analysis of variance” at first use.

Answer: Analysis of Variance One-Way (ANOVA) was added

2. Figure 1: Panels A, B, and C should be labeled. The X-axis label in panel B should be translated into English.

Answer: The requested revision has been implemented.

3. Section 3.1: Psyllid populations in this one-year trial were extremely low. The negative control averaged only about 0.5 psyllids per flush. In regions such as Florida, Mexico, and China, psyllid populations are typically much higher—even under heavy insecticide use. Results observed here may not hold under such higher densities. The authors should emphasize this limitation, particularly since the study was not replicated across years or locations. Generally, such trials should be conducted over at least two years or in multiple locations before recommendations can be made. I strongly advise against making broad claims about the usefulness of silicon against ACP based on one year of data from a site with unusually low populations. Importantly, no data were collected on whether silicon treatments affect transmission of the HLB pathogen. This remains a critical unanswered question.

Answer: A correction has been made to the graph, which previously did not display values as percentages. Specifically, an incidence value of 0.5 corresponds to 50%. We appreciate the observation and have addressed it accordingly.

In this study, it was not possible to assess the effect of silicon on pathogen transmission, as Huanglongbing (HLB) is not present in the study area. The primary objective was to explore alternative strategies for vector management. We acknowledge that evaluating the interaction between silicon, the vector, and pathogen transmission is a critical research question. Therefore, future studies should be conducted in regions where HLB is established, allowing for a comprehensive analysis of silicon’s role in disease suppression.

Nonetheless, the findings presented here offer preliminary evidence supporting the potential of silicon as a preventative tool in integrated insect management programs.

4. Figure 3: Both X and Y axis labels are missing and should be provided

Answer: The requested revision has been implemented.

5. Lines 284–287: The current sentence suggests that the study measured oviposition, nymph weight, or feeding rates, which it did not. This should be re-written to avoid that implication.

Answer: The sentence has been revised to improve clarity and alignment with the study’s findings. The updated version more accurately reflects the intended meaning and ensures consistency with the terminology used throughout the manuscript. Located on page 10, lines 294–295.

6. Lines 320–340: This section consists of many short, individual statements. These should be consolidated into more cohesive, integrated paragraphs.

Answer: The indicated modifications have been implemented in the section located on pages 11–12, lines 324–349. Specifically, the text was revised to improve clarity, ensure terminological consistency, and enhance alignment with the study’s objectives. Adjustments included refining the description of the experimental procedures, correcting terminology related to vector management strategies, and clarifying the interpretation of the results.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

General comments

In this study, the authors evaluated the effect of two silicon sources and three application methods on the psyllid oviposition and development, the chemical properties of the soil, and foliar nutrient uptake in a Tahiti lime orchard. The results reveal that silicon not only can be used as an alternative method for the management of psyllid, but also positively influenced the nutrient content in the soil and foliar tissue, fruit weight, size, and juice yield. The results of this present study are interesting and important. However, there are writing and logical issues. 

Major comments

The Abstract is complicated to read and should be simplified. Please read carefully the journal instructions for authors that there is a word limit for the research article.

Line 13-16: The aim of the study is poorly presented. Please refer to Line 68-70.

Line 38: Authors should give the brief introduction to asian citrus psyllid.

The results section shall lose weight. Only the key information is needed. Furthermore, some sentences should move the discussion section, such as Line 157, Line 166-167, Line 193-197, Line 226-228.

Discussion part, the author missed an important reference “Silicon accumulation in maize and its effects on demographical traits of fall armyworm, [Spodoptera frugiperda (J. E. Smith)]”. The author should discuss more information with this reference.

Conclusions should be simplified.

Minor comments

Format issues:

Line 90, Table1: Please keep the unit format consistent: 2 mL L^-1 or 2 ml L^-1?

Line 99: “infestation began, aided by a 30x” is bold font?

Line 130: P value should be in italics, see also Line 136, Line 140, … Please check and revise carefully the whole manuscript.

Line 140: add the space before “=”. See also Line 209, Line 214, … Please check and revise carefully the whole manuscript.

Line 189: r value should be in italics, please check and revise carefully the whole manuscript.

Line 263: Figure 3, The X-axis can be adjusted, such as by rotating it to make the graph more aesthetically pleasing.

References: The capital letters and lowercase letters of the first letter of each reference term in the list should be consistent throughout. For example: Line 404, Line 416.

Comments on the Quality of English Language

The language is professional but at times overwrought and cumbersome, particularly due to the length of some sentences. Shortening sentences and simplifying syntax could improve readability.

Author Response

Reviewer 2

Major comments:

1. The Abstract is complicated to read and should be simplified. Please read carefully the journal instructions for authors that there is a word limit for the research article.

Answer: The abstract has been revised in accordance with the journal’s guidelines. The modifications were made to enhance clarity, ensure alignment with the scope of the study, and meet the structural and formatting requirements specified by the editorial standards.

2. Line 13-16: The aim of the study is poorly presented. Please refer to Line 68-70.

Answer: The study objective has been revised in both the abstract and the introduction to ensure consistency and alignment with the scope of the research. The modification in the introduction section is located on page 2, lines 67–69, and clarifies the specific aim of the study, emphasizing its focus on evaluating alternative strategies for vector management rather than pathogen transmission, given the absence of Huanglongbing in the study area.

3. Line 38: Authors should give the brief introduction to asian citrus psyllid.

Answer: The importance of both the insect vector and the associated disease has been incorporated into the introduction section to provide a more comprehensive context for the study. These revisions, located on page 1-2, lines 32–43, emphasize the epidemiological relevance of the vector in citrus production systems and the potential impact of Huanglongbing (HLB) where the disease is present. This enhancement strengthens the rationale for the research and aligns the introduction with the study’s objectives regarding vector management strategies.

4. The results section shall lose weight. Only the key information is needed. Furthermore, some sentences should move the discussion section, such as Line 157, Line 166-167, Line 193-197, Line 226-228.

Answer: The necessary corrections have been made. Specifically, citations within the results section have been reviewed and updated to ensure accuracy, proper attribution, and consistency with the journal’s referencing format.

5. Discussion part, the author missed an important reference “Silicon accumulation in maize and its effects on demographical traits of fall armyworm, [Spodoptera frugiperda (J. E. Smith)]”. The author should discuss more information with this reference.

Answer: A suggested reference, along with its interpretation, has been incorporated into the manuscript to strengthen the discussion and support the findings. This addition is located on page 10, lines 281–284, and provides relevant context that enhances the scientific foundation of the section.

6. Conclusions should be simplified.

Answer: The conclusions section has been updated

 

Minor comments:

• Format issues: Line 90, Table1: Please keep the unit format consistent: 2 mL L-1 or 2 ml L-1? Line 99: “infestation began, aided by a 30x” is bold font? Line 130: P value should be in italics, see also Line 136, Line 140, … Please check and revise carefully the whole manuscript.  Line 140: add the space before “=”. See also Line 209, Line 214, … Please check and revise carefully the whole manuscript. Line 189: r value should be in italics, please check and revise carefully the whole manuscript. Line 263: Figure 3, The X-axis can be adjusted, such as by rotating it to make the graph more aesthetically pleasing. References: The capital letters and lowercase letters of the first letter of each reference term in the list should be consistent throughout. For example: Line 404, Line 416.

Answer: All of the proposed changes have been successfully incorporated.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

The manuscript presented requires improvement, as indicated below.

Introduction:

The introduction needs to be supplemented and provide readers with a more detailed introduction to the subject matter. For example, it would be worth adding why it is so important to combat Diaphorina citri. Examples of losses caused by Huanglongbing (HLB) and its impact on crops.

Materials and Methods:

I suggest dividing the “Materials and Methods” section into subsections—this will make it easier for readers to follow.

The study involved an induced infection with D. citri (lines 120-121) – where did the D. citri come from? I cannot see any details in the methodology.

The data presented shows that elements were tested in the soil, but I cannot see in the methodology what method was used or a description of this method—this should be clarified.

Overall, the methodology lacks detail—after adding subsections, please describe in detail the research that was conducted in each of them.

Results:

Figure 1 is too small and therefore illegible; it should be enlarged. The graphs can be placed one below the other.

In general, if the authors have decided to present the results separately and the discussion in a separate chapter, they should be consistent. In some places in the results section, the authors discuss a given result or compare it with other authors. If these are two separate chapters, they must be separated.

Discussion:

Paragraphs 305-310 contain repetitions from paragraphs 311-319—please rearrange and remove the repetitions.

 

Author Response

Reviewer 3

1. Introduction:

• The introduction needs to be supplemented and provide readers with a more detailed introduction to the subject matter. For example, it would be worth adding why it is so important to combat Diaphorina citri. Examples of losses caused by Huanglongbing (HLB) and its impact on crops.

Answer: The relevance of the pathosystem has been thoroughly addressed and incorporated into the manuscript. The importance of both the insect vector and the associated disease has been incorporated into the introduction section to provide a more comprehensive context for the study. These revisions, located on page 1-2, lines 32–43, emphasize the epidemiological relevance of the vector in citrus production systems and the potential impact of Huanglongbing (HLB) where the disease is present. This enhancement strengthens the rationale for the research and aligns the introduction with the study’s objectives regarding vector management strategies.

 

2. Materials and Methods:

• I suggest dividing the “Materials and Methods” section into subsections—this will make it easier for readers to follow.

Answer: The required modification has been applied accordingly.

• The study involved an induced infection with D. citri (lines 120-121) – where did the D. citri come from? I cannot see any details in the methodology.

Answer: The source has been added, and the wording has been refined in lines 135–138 on page 4.

• The data presented shows that elements were tested in the soil, but I cannot see in the methodology what method was used or a description of this method—this should be clarified.

Answer: The methods employed for soil and tissue analysis have been incorporated into the manuscript, specifically in lines 111–121 on page 3.

• Overall, the methodology lacks detail—after adding subsections, please describe in detail the research that was conducted in each of them.

Answer: Additional details have been provided to enhance the description of the methodology.

 

3. Results:

• Figure 1 is too small and therefore illegible; it should be enlarged. The graphs can be placed one below the other.

Answer: It was modified

• In general, if the authors have decided to present the results separately and the discussion in a separate chapter, they should be consistent. In some places in the results section, the authors discuss a given result or compare it with other authors. If these are two separate chapters, they must be separated.

Answer: Necessary corrections and revisions have been applied.

4. Discussion:

• Paragraphs 305-310 contain repetitions from paragraphs 311-319—please rearrange and remove the repetitions.

Answer: Revisions and corrections have been made to the content on page 11, lines 303–321.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

The authors have adequately addressed all the concerns raised during the review process. They have provided satisfactory clarifications and made the necessary revisions to improve the manuscript.  I have no further comments and therefore recommend the manuscript be accepted for publication. Congratulations to the authors!

Reviewer 3 Report

Comments and Suggestions for Authors

The authors have addressed all comments in the review and revised the manuscript, which is now significantly improved.