Glyphosate Excessive Use Affects Citrus Growth and Yield: The Vicious (and Unsustainable) Circle in Brazilian Orchards

Round 1

Reviewer 1 Report

Dear authors,

I find the manuscript very interesting and I only suggest some minor changes in order to improve the article. I only feel like there might be some mention about alternative control methods to be combined with glyphosate in order to decrease the use of this (this could be solved with one or two additional sentences). And I have de doubth if glyphosate really has o not any residual effect. In the manuscript it is stated that it has not, but there are references that suggest some... maybe not beeing so unquestionable about this aspect would also be enough.

Sincerely,

Comments for author File: Comments.pdf

Author Response

Dear Revisor,

 We carefully considered your comments, and we want to extend our appreciation, for taking the time and effort necessary to provide guidance.

Overall, we have rewritten the erroneous English statements with your help and the latest version is much more coherent and cohesive.

For the major concerns that you indicate, here we demonstrate our responses:

About the residual effect of glyphosate, as you mentioned:

“are you sure of this assumption? see Cornish and Brugin, 2005, Residual effects of glyphosate herbicide in ecological restoration (Restoration Ecology 13, 695-702) and others.”;

 And “then, there is a residual effect?”

RESPONSE: I have clarified the sentence as glyphosate is in general, AS A LOW RESIDUAL HERBICIDE (referencing the revision by Duke (2020)), as you concerned: “And I have de doubth if glyphosate really has o not any residual effect. In the manuscript it is stated that it has not, but there are references that suggest some... maybe not beeing so unquestionable about this aspect would also be enough.”

So, it became like this:

“Secondly, also because this herbicide has a low residual effect on soils (it is more tightly bound to soils than most other herbicides) [2], there may be a selection of short-cycle and/or late germination species that develops in the application intervals, predominating in the weed seed bank [33].”

About the complementation of glyphosate with other methods:

“what about combining glyphosate with other control methods, such as mulches or living cover crops? is that feasible in Brazilian citrus orchards?”

“I would appreciate a kind of discussion about this issue, as you have previously mentioned Integrated Weed Management.”

“exactly!!! could you mention or proposed any to combine with glyphosate?”

RESPONSE: We added some information about a management strategy that some of the authors of the present study have also published on Weed Technology (https://doi.org/10.1017/wet.2017.3). So we believe that this new sentence (in blue) consolidates your previous concerns.

“Therefore, an herbicides program should be used with different mechanisms of action in which glyphosate can be inserted at dosages that do not intoxicate the crop, and in association with other control methods, which rely on integrated weed management (IWM) principles. For example, ecological mowing proved to be an IWM option for citrus, also within FAO preconized CA premises, as this management strategy produces an in-situ mulch by the deposition of the mowed cover crop biomass on the tree-row, enhancing weed control and the citrus growth and fruit yield”

Thank you for taking the time and energy to help us improve our paper.

Sincerely,

The authors

Reviewer 2 Report

Manuscript requires a few changes to make it more readable.

-Authors may want to change the word intoxication for phytotoxicity. Intoxication refers more to humans.

-Authors  need to standardize scientific names through manuscript. See L20-21 vs 159-160.

Figure 1. Second image, it looks like authors photographed a grass weed species, and stated it is resistant, why it was not considered in the dose response experiments? 

Higher weed resistance or higher resistance levels?

What readers have to see in the last picture?

L81. Please correct, there is typo error.

L130. Is this number correct according to the values provided (0.9 ha)?

L155-156. Please re-phrase to avoid misunderstanding of "control" which has two different meanings here.

L160-161. Is not clear how authors collected the seeds? Was it a pool of surviving plants? what distance among plants? was it collected on all treatments?

Authors need to explain the greenhouse conditions for those experiments.

L198. Please clarify how authors choose the plants for measurements? were all plants measured?

L230. X is a variable-response in this equation?

Table 1. Please clarify the df on weed control compared to Phytotoxicity, Canopy....

Figure 3. RAPRA survival we only have one line, guess corresponds to one biotype, is this correct? or all biotypes had exactly the same response across all rates tested? 

L317 typo error.

L587. Delete So, for the first time in the literature, the. Or begin with other sentence. There are many reports on the literature regarding glyphosate and its use in different cropping systems.

Author Response

We carefully considered your comments, and we want to extend our appreciation, for taking the time and effort necessary to provide guidance.

Overall, we have rewritten the erroneous English statements and the latest version is much more coherent and cohesive.

For the concerns that you indicate (excluding the punctuation errors), here we demonstrate our responses:

-Authors may want to change the word intoxication for phytotoxicity. Intoxication refers more to humans.

RESPONSE: OK, it is done.

-Authors need to standardize scientific names through manuscript. See L20-21 vs 159-160.

RESPONSE: OK, it is done.

Figure 1. Second image, it looks like authors photographed a grass weed species, and stated it is resistant, why it was not considered in the dose response experiments? 

RESPONSE: These photos are from commercial groves and not from the experimental area, which is used only as a didactic context. I have also added this on the figure legend: “The photos are from reports of citrus growers after glyphosate use.”

Higher weed resistance or higher resistance levels?

RESPONSE: I have rewritten on the figure, thank you for the valuable suggestion.

What readers have to see in the last picture?

RESPONSE: The last figure complements the Canopy Volume data, as readers can relate the height and diameter as the “Arrows indicate the height of 2.0m on the graduate scale” (I have clarified this on the figure legend).

L130. Is this number correct according to the values provided (0.9 ha)?

RESPONSE: I have corrected. It is 0.63 ha and 0.9 ha with the border lines.

L155-156. Please re-phrase to avoid misunderstanding of "control" which has two different meanings here.

RESPONSE: I have rewritten, thank you for the valuable suggestion.

L160-161. Is not clear how authors collected the seeds? Was it a pool of surviving plants? what distance among plants? was it collected on all treatments?

RESPONSE: I have added where and how it were collected rewritten, thank you for the valuable suggestion!

Authors need to explain the greenhouse conditions for those experiments.

RESPONSE: OK, it is done. Thank you for this. I’ve added information about greenhouse location and irrigation management.    

L198. Please clarify how authors choose the plants for measurements? were all plants measured?

RESPONSE: Ok, it is done. I have added: … “height and diameter of the canopy of the two central trees of each plot using”

L230. X is a variable-response in this equation?

RESPONSE: I have clarified this.

Table 1. Please clarify the df on weed control compared to Phytotoxicity, Canopy....

RESPONSE: I have clarified this.

Figure 3. RAPRA survival we only have one line, guess corresponds to one biotype, is this correct? or all biotypes had exactly the same response across all rates tested? 

RESPONSE: It is superimposed because they had the same response across all rates tested.

L587. Delete So, for the first time in the literature, the. Or begin with other sentence. There are many reports on the literature regarding glyphosate and its use in different cropping systems.

RESPONSE: I have rewritten: “The present study shows for the first time in the literature the results of the excessive use of glyphosate and its implications in a citrus orchard.”

Thank you for taking the time and energy to help us improve our paper.

Sincerely,

The authors