Herbicide Resistance in Summer Annual Weeds of Australia’s Northern Grains Region

Round 1

Reviewer 1 Report

 

This manuscript examines the occurrence of herbicide resistance in summer annual weeds of Australia’s northern grains region. This study is relevant and describes the state of herbicide resistance in key crop weeds of an important Australian region.

Minor comments and suggestions are included in the attached file.

 

Comments for author File: Comments.pdf

Author Response

Line 99            Map-making software

                        Have added software and reference

Line 106          I suggest adding information about the number of plants collected from each population.

The number of plants is not recorded and varies according to density, have added that between 10 and 15 minutes was spent sampling each site

Line 156          I suggest including information about how many trays/plants were included in each repetition

                        This is mentioned in Section 2.2

Line 158          I suggest including information about how many trays/plants were included in each repetition

                        Have added in section 2.2 the full CSU methodology which includes replicates and plants per replicate

Line 159          Please describe the specific conditions being referred to.

Have added reference to Section 2.2 and Section 2.3 to define the growing and herbicide application conditions

Line 168          Is this an arbitrary decision? Is there any precedent in the literature?

All Australian publications use a survival percentage of 20% to define a population as resistant, have added references to show this and one that specifies why

Line 184          Figure 4 refers to sowthistle populations

Have removed reference to figure 4, no figure included for this species due to small number of collected populations

Line 228          Figure 4 refers to sowthistle populations

Have removed reference to figure 4, no figure included for this species due to small number of collected populations

Line 339          Reference numbers are duplicated

                        Reference list has been formatted to remove duplicate numbers

Line 339          The link is not working

                        Have changed reference to show updates web address

Reviewer 2 Report

Good, important research! 

The following minor editorial issues need attention:

Lines 104-105: The description of density ranges provided here does not fit the table column headings in Table 2.

Lines 104-105: The "-2" in the unit for square meter must be made superscript.

Line 187 (heading of Table 2): The spelling of "ranges" should be "range".

Consistency in spelling: Note that "glyphosate-resistant" is generally used instead of "glyphosate resistant". Hyphen to be introduced at the following lines of text: 190; 193; 197; 201; 224; 229; 245; 254; 276; 306 (there could be more!).

Line: 294: remove the hyphen in "chlorsulfuron-resistance".

Note: I did not check for conformance to journal guidelines for authors.

 

 

Author Response

Lines 104-105: The description of density ranges provided here does not fit the table column headings in Table 2.

Change has been made

Lines 104-105: The "-2" in the unit for square meter must be made superscript.

Changes have been made

Line 187 (heading of Table 2): The spelling of "ranges" should be "range".

Change has been made

Consistency in spelling: Note that "glyphosate-resistant" is generally used instead of "glyphosate resistant". Hyphen to be introduced at the following lines of text: 190; 193; 197; 201; 224; 229; 245; 254; 276; 306 (there could be more!).

The spelling glyphosate-resistant only applies when referring to glyphosate-resistant crops, for resistant weeds it is glyphosate resistant (no hyphen) same as suggested for chlorsulfuron resistant below

Line: 294: remove the hyphen in "chlorsulfuron-resistance".

Change has been made

Reviewer 3 Report

After read the paper twice, this is my opinion:

An interesting study from a regional point of view.

It is outdated now, however it may be useful in a few years in a comparative study carried out in the same regions.

 

Author Response

An interesting study from a regional point of view.

It is outdated now, however, it may be useful in a few years in a comparative study carried out in the same regions.

Results from any survey represent a “snapshot in time” of the current situation, therefore as the survey results presented here represent the herbicide resistance status of weed populations in 2016/17, five years later they are likely to be somewhat “outdated”. Regardless, the results presented are for the first-ever herbicide resistance survey of summer annual weed species in the northern grains region and, as the reviewer has recognized, represent a benchmark with which all subsequent surveys can be compared.

Reviewer 4 Report

This manuscript describes the results of weed surveys that were performed to assess the frequency of herbicide resistance among various weeds. The results are valuable and of interest, albeit somewhat out-of-date (the surveys were conducted from 2016 to 2018). Specific comments are below:

Line 11: In the abstract, please include the years that the surveys were conducted. This is important due to the likely increases in resistance frequency that have probably occurred since the surveys were performed.

Lines 26-27: While it would likely be helpful, I don’t think that incorporating non-chemical weed management can “ensure” sustainability of current herbicides, and the manuscript did not test nor cite other research supporting this claim. A more general statement such as the need for alternative weed control (see lines 320-323), would be better.

Lines 95-98: It’s not clear how the fields were selected at random (from a map before conducting the survey, or every so often based on distance traveled, or informally selecting fields at random as best as one could, etc.). Also, it’s not clear if landowners/managers were selected at random for permission, or if fields were selected at random and then permission was sought. Please clarify.

Lines 89-90: Clarify here that the surveys were conducted at crop maturity (as mentioned in line 172). This is important so that the reader knows that the plants surveyed were those that survived whatever weed control was performed in that field, rather than the whole population of weeds that were present before weed control. This is suggested in line 106, where seed heads are mentioned, but it could be clearer.

Lines 104-105 and Table 2: It would be good to describe the categories in such a manner that they don’t overlap (although I’m not sure it’s easy to do). For example, in line 104, an occasional plant fits into the very low category, but also would technically fit into the low category as well (<1 plant per m^2). In Table 2, <1 plant per 10 m^2 would also fit into the <1 plant per m^2 category. Also in Table 2, the >10 plants per m^2 heading is repeated. I think the second should include “and dominating the crop” (as in lines 105-106)?

Lines 286-290: Please clarify why the absence of crop competition intensifies selection pressure for glyphosate resistance. Is this because surviving resistant weeds produce more seed in the absence of crop competition? Please explain and/or cite a reference.

Line 301: Since this study was done several years ago, it’s not appropriate to say “at present” especially since resistance frequencies have probably changed.

The manuscript could benefit from minor polishing of grammar, but is overall well written. There are instances where "-1" or "-2" should be superscript, such as line 104, 130, etc.

Author Response

This manuscript describes the results of weed surveys that were performed to assess the frequency of herbicide resistance among various weeds. The results are valuable and of interest, albeit somewhat out-of-date (the surveys were conducted from 2016 to 2018). Specific comments are below:

Yes the results are somewhat dated but will be valuable for comparison with future survey results. 

Line 11: In the abstract, please include the years that the surveys were conducted. This is important due to the likely increases in resistance frequency that have probably occurred since the surveys were performed.

The dates have been added to the abstract

Lines 26-27: While it would likely be helpful, I don’t think that incorporating non-chemical weed management can “ensure” sustainability of current herbicides, and the manuscript did not test nor cite other research supporting this claim. A more general statement such as the need for alternative weed control (see lines 320-323), would be better.

Have changed ‘ensure’ to ’promote the’

Lines 95-98: It’s not clear how the fields were selected at random (from a map before conducting the survey, or every so often based on distance traveled, or informally selecting fields at random as best as one could, etc.). Also, it’s not clear if landowners/managers were selected at random for permission, or if fields were selected at random and then permission was sought. Please clarify.

Have attempted to clarify this but both methods of selecting fields were used. In NSW fields were selected at random at an approximate distance along a transect with no contact with landowners. In Queensland landowners/managers were contacted from a list of names collected via a third party (advisor, field day attendance etc)

Lines 89-90: Clarify here that the surveys were conducted at crop maturity (as mentioned in line 172). This is important so that the reader knows that the plants surveyed were those that survived whatever weed control was performed in that field, rather than the whole population of weeds that were present before weed control. This is suggested in line 106, where seed heads are mentioned, but it could be clearer.

                        Have added ‘at crop maturity’ here as well

Lines 104-105 and Table 2: It would be good to describe the categories in such a manner that they don’t overlap (although I’m not sure it’s easy to do). For example, in line 104, an occasional plant fits into the very low category, but also would technically fit into the low category as well (<1 plant per m^2). In Table 2, <1 plant per 10 m^2 would also fit into the <1 plant per m^2 category. Also in Table 2, the >10 plants per m^2 heading is repeated. I think the second should include “and dominating the crop” (as in lines 105-106)?

Have changed first category to occasional plant and added ‘and dominating crop’ to last category to remove repetition

Lines 286-290: Please clarify why the absence of crop competition intensifies selection pressure for glyphosate resistance. Is this because surviving resistant weeds produce more seed in the absence of crop competition? Please explain and/or cite a reference.

Have explained why with two references cited

Line 301: Since this study was done several years ago, it’s not appropriate to say “at present” especially since resistance frequencies have probably changed.

                        Have changed ‘present’ to ’this time’

 

Comments on the Quality of English Language

The manuscript could benefit from minor polishing of grammar, but is overall well written. There are instances where "-1" or "-2" should be superscript, such as line 104, 130, etc.

Have changed all to superscript where appropriate

Round 2

Reviewer 3 Report

 Perhaps one day this study will be useful...

Author Response

thanks for your work