Potential global distribution of Aleurocanthus woglumi considering climate change and irrigation

variables that can signal if and when the plan needs to be activated, or at least be reconsidered in the light of shifting circumstances. It is easy to identify low-cost, no regrets management options for A. woglumi. For example, in the case of A. woglumi biosecurity, while the present threat to New Zealand appears low due to excessive cold stress during winter, this protection appears vulnerable to climate change within the next thirty years. Unless costs are prohibitive, phytosanitary measures to prevent the spread of A. woglumi to New Zealand would seem reasonable under present climatic con- ditions, potentially avoiding seasonal market access issues if there were an incursion. These same measures would also help prevent the potential establishment of this pest in the future as the winter protection is eroded by a warming climate. Currently, with good reason, Australia maintains phytosanitary measures to prevent the entry and establishment of A. woglumi. The present invasion threat posed by A. woglumi to Europe encompasses most of the cit- rus-growing regions in the Mediterranean Basin. The threat appears set to expand northwards with further climate change. It would seem prudent to try to prevent the establishment of A. woglumi in Europe, North Africa and the Middle East. The Nile Valley (Fig 1) poses an obvious invasion pathway towards Europe, alongside the movement of trade goods via shipping from sub-Saharan Africa via coastal Atlantic and Suez Canal routes. The expansion of irrigation in

the Arabian Peninsula has created an additional set of stepping-stones for biological invasions to the north. In North America, it would seem sensible to try to limit the spread of A. woglumi from Texas and Florida into Arizona and California where there are valuable citrus production areas. Under current climatic conditions, California and Arizona appear unsuitable for A. woglumi to persist, though with a warming climate this situation appears set to change. In con- trast to Australia and New Zealand, where there are maritime borders, quarantine measures to restrict the movement of A. woglumi across state borders may be infeasible, cost-prohibitive, or politically unpalatable. Given the difficulty and expense of eradication efforts, there may be value in undertaking pre-emptive biological control preparations, undertaking host specificity testing of candidate agents such as Encarsia perplexa and Amitus hesperidum [72,73]. Such Hymenopteran para- sites have been proved economical and effective because they kept A. woglumi below damaging levels in much of its distribution range in several parts of the world like southern Florida [74], Trinidad & Tobago [72], Texas [75], Mexico [76] and Dominica [73]. In an exciting development, New Zealand has established conditional approval for the import and deployment of Trissolcus japonicus, a biological control agent for Halyomorpha halys [77]. The New Zealand Government recognised the invasion threat posed by H. halys and supported the testing and approval ahead of the arrival of H. halys. The foresight provided

by the analyses in this paper could be used to justify such a programme for A. woglumi and provide a basis for countries to join together to complete host-specificity testing, taking advan- tage of economies of scale. Supporting information S1 Fig. Modelled global climate suitability for Aleurocanthus woglumi as a composite of natural rainfall and irrigation scenarios based on irrigation areas identified by Siebert et al. [64]. The Ecoclimatic Index (EI) describes the overall climate suitability for population persistence, where 0 is unsuitable and 100 is year-round optimal conditions. Black dots indi- cate location records for A. woglumi and black polygons the administrative areas where A. woglumi has been reported (S1 Table). Purple shaded areas are those that are modelled as suit- able for A. woglumi only under the irrigation scenario. This map was produced by the authors PLOS ONE Potential global distribution of Aleurocanthus woglumi PLOS ONE | https://doi.org/10.1371/journal.pone.0261626 December 20, 2021 12 / 18