The Past, Present, and Future of Barley Yellow Dwarf Management
Round 1
Reviewer 1 Report
The manuscript by Walls et al. provides an important update and review of barley yellow dwarf, as the last comprehensive review was published in 1995. Overall the ms is informative, and several sections are strong. History of BYD, BYD Virus Taxonomy, Current Management of BYD, and Future Management of BYD are robust sections. However, , a few sections need some re-writing because they are unclear or contain some inaccuracies or overgeneralizations. Altogether, major revision is needed, as follows.
Although the ms provides information on the status of BYD in several areas of the globe, some sections are biased toward the northern hemisphere or rely too heavily on information from Italy [24] or the United States. Some parts have info that contradicts statements from other parts of the ms.
Intro. Incidence and seriousness of BYD: Contradictions. The authors use % yield loss estimates for “areas prone to viral infestation” (li 30-31) to project “a conservative GLOBAL” estimate of BYD yield loss. This new estimate needs to be scaled back to realistic levels.
“Disease management often begins with symptom identification” li. 100-101. Later in the ms, the authors discuss how disease management is primarily preventative. The latter is more accurate, because by the time visual symptoms have been identified, disease management is likely too late, as there are no good remedial tactics. So, l. 100-101 need to be removed.
Vector Biology. Largely based on ref #24 from Italy—a relatively small wheat producing area from which to generalize. Revise with a more general ref.
li. 142-3 unclear with reference to temperature, and the temp-flight threshold explanation is too detailed for this review. Revise.
l. 152 The reference to months of Aug, Sep & Oct reflects bias toward temperate growing regions in No. Hemisphere---this peculiarization should be avoided. Revise.
li. 153-4 Night and day temps not always that different. Besides there are other drivers here.
Vector-Host Plant Interactions. 1) Schizaphis graminum is missing from this section. 2) Define secondary hosts and briefly explain host alternation. Explain why knowing the primary host is important, but also note that many of the vectors persist year-round only on secondary hosts. 3) Maize is not the primary host of R. maidis. 4) Li. 191 “Different aphid species…” is not informative as a topic sentence.
History of BYD Management. 1) Is insecticide seed treatment effective after only 2 weeks (li. 222) or for a few weeks (li. 225)? 2) Please clarify how I seed treatment, which last only 2 to a few weeks, can impact pollinators when wheat is a wind- and self-pollinated grass and how the treatments might affect other beneficial insects—these statements are not supported here (and in li. 406).
BYD Virus Resistance. 1) Introduce this section by briefly defining the categories of resistance against vectors and against BYD viruses. 2) li. 272-276. I don’t understand the point here. Is the point that transgenic wheat varieties were ahead of their time? Is this the right time to reconsider them for BYD management?
Misspellings, Grammatical errors. Some references incorrectly formatted.
Author Response
Thank you for the advice. We agree with the edits requested and have hopefully adequately addressed all of the issues.
Revisions
Reviewer 1:
1. Although the ms provides information on the status of BYD in several areas of the globe, some sections are biased toward the northern hemisphere or rely too heavily on information from Italy [24] or the United States. Some parts have info that contradicts statements from other parts of the ms.
1) The information in the manuscript is biased towards the northern hemisphere because that is what we had access to. We contacted several experts in the southern hemisphere, but did not get responses, so we did not want to make assumptions without knowing the status and impact of the disease. As for the rest of the manuscript, most of the publications on the disease is biased towards the northern hemisphere. We went through the manuscript and tried to correct any contradictions that we found.
2. Intro. Incidence and seriousness of BYD: Contradictions. The authors use % yield loss estimates for “areas prone to viral infestation” (li 30-31) to project “a conservative GLOBAL” estimate of BYD yield loss. This new estimate needs to be scaled back to realistic levels.
1) This estimate was removed because it is contradictory and there is no good source to estimate actual global yield losses due to the virus.
3. “Disease management often begins with symptom identification” li. 100-101. Later in the ms, the authors discuss how disease management is primarily preventative. The latter is more accurate, because by the time visual symptoms have been identified, disease management is likely too late, as there are no good remedial tactics. So, l. 100-101 need to be removed.
1) Added “…so that preventative measures may be taken the following season as once symptoms are present it is usually too late to manage the virus.” This was the intended message because growers should not be managing for a virus that is not present.
4. Vector Biology. Largely based on ref #24 from Italy—a relatively small wheat producing area from which to generalize. Revise with a more general ref.
1) Several references validating statements have been added to this section.
5. li. 142-3 unclear with reference to temperature, and the temp-flight threshold explanation is too detailed for this review. Revise.
1) Sentence changed to “Alate aphids have a threshold ambient temperature at which internal body temperature is high enough to allow flight muscles to function.” Part of the paragraph talking about the specifics of temperature threshold for take-off was removed.
6. l. 152 The reference to months of Aug, Sep & Oct reflects bias toward temperate growing regions in No. Hemisphere---this peculiarization should be avoided. Revise.
1) “…in August, September, and October…” removed
7. li. 153-4 Night and day temps not always that different. Besides there are other drivers here.
1) Added “…usually…” to say that in most regions the night temperature will be lower than the day. Added “However, other factors, such as light intensity, affect take-off as well [31]. Thus, simply because the temperature threshold is met does not necessarily mean the aphids will immediately take flight.”
8. Vector-Host Plant Interactions. 1) Schizaphis graminum is missing from this section. 2) Define secondary hosts and briefly explain host alternation. Explain why knowing the primary host is important, but also note that many of the vectors persist year-round only on secondary hosts. 3) Maize is not the primary host of R. maidis. 4) Li. 191 “Different aphid species…” is not informative as a topic sentence.
1) Added references to Sc. graminum in the section
2) Defined secondary host and explained the importance of primary host. C. d. Changed the section to explain that R. maidis has no primary host as it is only found to reproduce asexually. Added that when the primary hosts are not present, the vectors persist year-round only on the secondary hosts.
3) Changed to express this point
4) Changed from ‘Different’ to ‘These four’. Added a section on competition on infected vs. uninfected plants (Porras et al. 2018)
9. History of BYD Management. 1) Is insecticide seed treatment effective after only 2 weeks (li. 222) or for a few weeks (li. 225)? 2) Please clarify how I seed treatment, which last only 2 to a few weeks, can impact pollinators when wheat is a wind- and self-pollinated grass and how the treatments might affect other beneficial insects—these statements are not supported here (and in li. 406)
1) Added McCornack and Ragsdale (2006) reference to show that efficacy of neonic seed treatments may last up to 5 weeks.
2) Added “Krupke et al. (2012) [66] showed in their study that bees that visited maize, a wind-pollinated crop, that had been seed-treated with neonicotinoids showed high mortality with neonics in their systems. Bees also use cereal crops, such as wheat, to collect pollen, thus the presence of neonic seed-treatment is likely to have a similar effect.”
10. BYD Virus Resistance. 1) Introduce this section by briefly defining the categories of resistance against vectors and against BYD viruses. 2) li. 272-276. I don’t understand the point here. Is the point that transgenic wheat varieties were ahead of their time? Is this the right time to reconsider them for BYD management?
1) Short paragraph added at the beginning of this section to briefly explain the mechanisms of resistance.
2) This section was inference. The last sentence “Thus, it seems unlikely that these disease resistant cultivars will become a major player in BYD disease management strategies in the near future.” was removed since this is the author’s inference of the situation.
Author Response File: 
Author Response.docx
Reviewer 2 Report
This review briefly summarises the history, taxonomy, symptom development and various vector-virus-plant interactions before launching into current and future management issues. The early sections are very brief and while serving as an introduction to management, do not do the fields of research justice and I would advise they are expanded and made more comprehensive.
One area that deserves more attention is seasonal and regional effects which have a large effect on the use and reliability of models. For example, I know that in Australasia drought means that when grain prices rise farmers may be more likely to use insecticides (as they become more economic to use). If they are in a region that is not in drought this gives a good return.
Specific comments
Line
84 change to: or are unassigned.
86 kerII, and kerIII are these accepted names?
94 [10,15]
110-112 this sentence does not make sense!
159 Vector-Virus Interaction section
Include the role of symbiont and GROEL- like protein
201 change to: but only under extreme infestation [51].
209 change to: been managed through selection of resistant cultivars, planting date alteration, insecticidal seed treatments, and foliar insecticide sprays.
223 and onwards: include more detailed discussion of insecticides- neonicotinoids vs pyrethroids vs pirimicarb (affects aphids but less effect on beneficals).
224 change to: but success also depends on
225 change to: and the method used
229 effects on pollinators: is this relevant to wind pollinated crops such as cereals?
287 Current Management of BYD
Each section should be more explicit, are they just talking about wheat in each section?
345 Australia section
This is an oversimplification, BYDVs have not been beat here. Generalising about the whole of Australia based on the Western Australia experience is like making generalisations about the USA based on one state. BYDVs were a major production issue in the high rainfall areas of Western Australia, Victoria and Tasmania in 2011 and 2012.
350 change to: not as necessary as the pyrethroid sprays
References
12. incomplete
32. add # 578
50. incomplete
Author Response
Thank you for the advice. We agree with the edits requested and have hopefully adequately addressed all of the issues.
Reviewer 2:
1. 84 change to: or are unassigned.
a. Changed
2. 86 kerII, and kerIII are these accepted names?
a. These species names are accepted by the International Committee on Taxonomy of Viruses.
b. https://talk.ictvonline.org/taxonomy/; Family:Luteoviridae, Genus: Luteovirus
3. 94 [10,15]
a. Corrected
4. 110-112 this sentence does not make sense!
a. Sentence was removed.
5. Include the role of symbiont and GROEL- like protein
a. Added “Once in the hemocoel virions are bound by GroEL-like proteins synthesized by symbiotic bacteria, Buchnera spp. (van den Heuvel et al. 1999). The N terminal of the readthrough domain of the luteovirus coat protein binds specifically to the GroEL protein to prevent degradation in the aphid hemocoel and promotes the persistent transmission of the virus (van den Heuvel et al. 1997).”
6. 209 change to: been managed through selection of resistant cultivars, planting date alteration, insecticidal seed treatments, and foliar insecticide sprays.
a. Changed
7. 223 and onwards: include more detailed discussion of insecticides- neonicotinoids vs pyrethroids vs pirimicarb (affects aphids but less effect on beneficals).
a. Added “Typically pyrethroid foliar sprays are better to manage aphids, but pirimicarb may also be used at a lower efficacy (McKirdy and Jones 1996). Recently, however, S. avenae have developed resistance to pyrethroids (Dewar and Foster 2017). Pirimicarbs may give some protection to these resistance aphids, but neonicotinoids seem to be more effective (Dewar et al. 2014).”
8. 224 change to: but success also depends on
a. Changed
9. 225 change to: and the method used
a. Changed
10. 229 effects on pollinators: is this relevant to wind pollinated crops such as cereals?
a. Added “Krupke et al. (2012) [66] showed in their study that bees that visited maize, a wind-pollinated crop, that had been seed-treated with neonicotinoids showed high mortality with neonics in their systems. Bees also use cereal crops, such as wheat, to collect pollen, thus the presence of neonic seed-treatment is likely to have a similar effect.”
11. 287 Current Management of BYD: Each section should be more explicit, are they just talking about wheat in each section?
a. Specified in the introduction to this section that they are talking specifically about winter cereals.
12. 345 Australia section: This is an oversimplification, BYDVs have not been beat here. Generalising about the whole of Australia based on the Western Australia experience is like making generalisations about the USA based on one state. BYDVs were a major production issue in the high rainfall areas of Western Australia, Victoria and Tasmania in 2011 and 2012.
a. We changed the paragraph to more appropriately show that the disease has not been beaten in Australia, but that the tactics employed have had significant positive effect in the region.
13. 350 change to: not as necessary as the pyrethroid sprays
a. Changed
14. References
a. 12. Incomplete
i. Fixed
b. 32. add # 578
i. added
c. 50. Incomplete
i. Fixed
Author Response File: Author Response.docx
