Climate and the Global Spread and Impact of Bananas’ Black Leaf Sigatoka Disease

Round 1

Reviewer 1 Report

The study “ Climate and the Global Spread and Impact of Bananas' Black Leaf Sigatoka Disease”

is overall well structured, clear and focus a pertinent topic concerning air spread plant diseases and potential sources of first time infections.

In my opinion the figures and tables legends must be considerable improved. They have to stand on their own, the reader must be able to read the legend and understand what the numbers or curves mean and in this paper this is not possible. References must be formatted according to the journal style.

Some minor corrections in the methods, results and in the discussion sections could be made. Please see specific comments in the PDF attached.

Best wishes 

Comments for author File: Comments.pdf

Author Response

Thank you for the very helpful comments.  We have now addressed these as follows:

1.  We have added explanatory notes to all tables and figures.  

2.  We have formatted the references.  

3.  We have addressed the minor changes noted in the pdf file.  

Reviewer 2 Report

The authors present an empirical study of the global spread and impact of Bananas' Black Sigatoka Leaf Disease based on disease prediction models proposed by previous studies and studying different variables that can affect the BSLD. Among the most important are the international market (movement of plant material), the evolution of the appearance of the disease in the different producing countries or biophysical models, among others.

At first the authors place particular emphasis on what could be said to be a summary of the evolution of agriculture throughout history, ending with the green revolution, the decline in genetic diversity and the high inputs used. While everything they indicate in their introduction is true, it is no less true that today's agriculture in many areas of cultivation has little or nothing to do with that paradox. Today in Europe, for example, not only the number of permitted active substances has been significantly reduced, but integrated disease management has been widely implemented, and many microorganisms are even used as biological control of many pests and diseases. I believe that, if this part of the introduction is to be maintained, the reality of the current production system must be shown. On the other hand, when the authors talk about the increase in resistance to fungicides, they must include the bibliographical references that support it (line 86).

From a strictly epidemiological point of view, the temperature and humidity conditions required by the ascospores are a key factor in establishing the initial inoculum of the disease. However, what the authors do not seem to take into account in the model is this double condition of the ascospores, on the one hand as the initial point of the disease and on the other as a specific infection, since they are expelled from the ascospores at a specific time in the cycle, i.e. the specific temperature and humidity conditions are so during a specific period of time, not throughout the year. When a year comes dry or with low temperatures in spring, the disease is not expressed with such virulence precisely because of the low presence of primary inoculum. From this point onwards, several cycles of conidia (from asexual reproduction) will occur in the crop.

I fully understand the difficulty of modelling plant disease and that some of the interesting variables, even if they are important, could not be introduced in the model due to lack of data (such as UV radiation), but in the case of ascospores, the need to know the environmental conditions in that short period of time after the maturity of asci is fundamental to be able to predict the establishment and spread of the disease.

The feasibility of the model depends largely on this.

The authors are aware of the difficulty of modelling the disease and of the data that they have not been able to take into account, such as the time since the release of the ascospores and the arrival in the new area, ignorance of the real areas of the crop or local climatic variables, for example.

However, it is these climatic variables in the specific period of ascospores release which cast doubt on the model, since even with the introduction of inoculum by way of transport of plant material or any other route, the disease may not be expressed the following year if the environmental conditions are not suitable for the ripening of the asci and subsequent release of the ascospores. The authors should include this aspect and discuss it in the paper.

The conclusion of the paper also needs to be improved, it does not in my opinion reflect the most outstanding or remarkable aspects of the paper regarding the importance of the market for imported plant material versus other climatic factors in the prediction of the disease.

Author Response

Thank you very much for the very helpful comments and suggestions.   

1.  We have now added in the introduction that integrated pest management is now widely used (including a reference for this).  

2.  We now emphasize in the conclusion the important result of the crucial role that agricultural trade plays in disease diffusion.  

3.  With regard to the comment regarding the double condition of the ascospores, we actually do take account of this in that we only model the LDD conditions when the appropriate local climate is present.  We are now more clear about this in the description of the simplified disease model.  

4.  We have now included a reference in the introduction where we make the statement about the growing resistance to pesticides.