Dear Robert and co-authors,

Many thanks for the submission of the revised manuscript. As you are aware the manuscript attracted two contrasting reviews, one being rather critical. Referee #1 questioned the validity of some of the assumption and wanted to see more evidence to back up that VOC emissions in response to biotic stress are indeed leading to significant BSOA formation.

I agree with your response that there is sufficient merit in the paper by highlighting the potential of this pathway and providing a first sensitivity study rather than providing final proof. However, I also agree with Referee #1 that as currently written the manuscript may at places be misunderstood as providing an actual quantification of the effect. I would therefore like to ask you to revise the manuscript linguistically to make it even clearer that this is indeed a sensitivity study. If Referee #1 misinterprets this fact, so will other readers.

To highlight an example, in the abstract the sentence "The estimated current situation SIE in Central and Northern European forests are found to contribute substantially to SOA in large parts of Europe." may be re-phrased. "Based on estimates of current levels of infestation and the JPAC aerosol yields, the model suggests that the contribution to SOA in large parts of Europe may be substantial." There are other similar places in the manuscript where the language should be moderated.

In addition, the manuscipt would benefit from a clearer discussion of the limitations of the study, which includes the database of emissions and aerosol yields from which the effect is extrapolated. The authors should also discuss more clearly what effects may already have been implicitly treated in the past. For example, it is unclear to what extend SQT emission factors in the literature may already be affected by responses to biotic stress. In this context line 440 ("that neglects most biotic stress emissions.") should better read "that does not explicitly treat biotic stress emissions." By contrast, a clearer distinction can presumably be made for MeSA whose emissions and chemistry are not normally treated in CTMs.

The new text of line 156ff could be improved. I think it would be important to get the term 'pool emission' into this sentence. "This was made ..." is poor English.

I am looking forward to a carefully revised manuscript.

With best wishes,
Eiko.