Risk assessment of Resseliella citrifrugis for the EU

Abstract

Following a request from the European Commission, the EFSA Panel on Plant Health performed a risk assessment of the citrus fruit midge Resseliella citrifrugis (Diptera: Cecidomyiidae), an oligophagous species, which feeds on fruits of Citrus spp., and is reported from China. The pest was temporarily regulated in October 2022 (Regulation (EU) /1941 , under Art. 30 (2016 /2031). The entry risk assessment focused on the citrus fruit pathway. Three scenarios were considered: A0 (current practice, i.e. regulated pest for the EU), A1 (deregulation) and A2 (A0 with additional stand-alone post-harvest cold treatment). Based on the outputs of the entry model, under scenario A0, slightly less than 40 potential founder populations per year are expected (median; 90%-uncertainty interval between about one per 30 years and about 3,000 per year). Under scenario A1, the risk of entry increases by about three times and reaches about 120 potential founder populations per year (median; 90%-uncertainty interval between about one per 10 years and about 9,000 per year). Compared to scenario A0, the risk of entry is orders of magnitude lower for scenario A2 (median = about one potential founder population per 120 years; 90%-uncertainty interval between one per about 600 million years and about two per year). The main uncertainties in the entry assessment are the probability of transfer, the RRO effectiveness (for scenario A2) and the disaggregation of consignments (transport of citrus fruit in boxes or lots to different locations). For all scenarios, the number of established populations is only slightly lower than the number of potential founder populations. Establishment is thus not expected to be a major constraint for this pest to then spread and cause impacts, despite the uncertainty about the pest thermal requirements. The median lag period between establishment and spread is estimated to be about 18 months (90%-uncertainty interval between about 7 and 54 months). After the lag period, the median rate of spread by flying and due to transport of harvested citrus fruit from orchards to packinghouses is estimated at about 100 km/year (90%-range between about 40 and 500 km/year). The main uncertainties in the spread assessment include the level of susceptibility of cultivars of different citrus species in the EU, the spread rate in China and the climate suitability of the initial spread focus in the EU. The median impact of R. citrifrugis in the EU citrus-growing area (proportion of infested citrus fruit out of harvested citrus fruit) is estimated at about 10% (90%-uncertainty interval between about 2% and 25%). Uncertainties affecting the impact assessment include the susceptibility of different citrus cultivars and the effect of the citrus fruit-harvesting season in the EU (mainly winter, the less suitable season for the pest).

Including climate change in pest risk assessment: Current practices and perspectives for future implementation

“…Examples using this method are the work of Ni et al (2012) and Kistner-Thomas (2019) on Bactrocera zonata and Popillia japonica (the Japanese beetle), respectively, where the degree-days required for a generation were calculated for use in the CLIMEX modelling approach. Another example is the pest risk assessment on Resseliella citrifrugis (EFSA PLH Panel, 2023b), where a comparison of the sum of degree days between the regions with reports of the pest in China and the EU citrus growing area was performed. • Species distribution modelling (SDM).…”

Pest risk assessment of African Leucinodes species for the European Union

“…The Panel had to draw on information on the closely related species L. orbonalis from Asia and assume impacts would be the same. Whether the transferability of reports from Asia on impacts caused by L. orbonalis are truly applicable to African Leucinodes species is uncertain. Literature on impact of insect pests reports high values that may not accurately reflect expected impacts over a large area (EFSA PLH Panel, 2023). The Panel estimated expected impacts taking into account climate suitability in the EU as compared to hotter regions where Leucinodes spp.…”

“…The level of pest infestation in trade is often the largest uncertainty in quantitative pest risk assessments (e.g. EFSA PLH Panel, 2016a, 2016b, 2017a, 2017b, 2023, 2024). The next largest uncertainty in the model is the estimate of the proportion of adults that escape from discarded domestic waste and complete their development (14%).…”

“…Formerly, the Panel had agreed with the Commission to conduct an analysis of the consequences of climate change for Elasmopalpus lignosellus (EFSA PLH Panel, 2023) and not for species of Leucinodes as was specified in the terms of reference. After having seen the results of the analysis for current climate conditions, the Panel judged it appropriate to invest nevertheless in an analysis of climate change consequences for the risk of African species of Leucinodes .…”

Pest risk assessment of Leucinodes orbonalis for the European Union

“…In addition, as agreed with the Commission, the effect of climate change will not be examined for L. orbonalis as it has instead been assessed previously for Elasmopalpus lignosellus Zeller (Lepidoptera: Pyralidae) (EFSA PLH Panel, 2023). A brief discussion on consequences of climate change is given in Section 3.6.…”