Abstract. Insect pests pose a great threat to global food security. Improved methods for assessment of the risk of pest establishment are needed to enhance informed decision-making, to develop cost-effective pest management strategies, and to design quarantine policies for preventing the spread of pests. We evaluated the capabilities of a correlative and a process-based mechanistic niche model, and their combination, to assess the risk of pest establishment. The correlative model MaxEnt and the process-based mechanistic model CLIMEX were used to assess the risk of establishment of western cherry fruit fly, Rhagoletis indifferens Curran (Diptera: Tephritidae) in California. We integrated R. indifferens occurrence records and spatial environmental variables using MaxEnt to assess the potential risk of establishment of this pest. The CLIMEX model was developed using eco-physiological tolerances of R. indifferens. The predictive performance of the MaxEnt model improved by including the host species' distribution and Ecoclimatic Index generated using the CLIMEX model. The best model predicted no risk for R. indifferens establishment in the Central Valley around the areas where sweet cherries are produced in California. Most of the high to very high risk areas for R. indifferens were predicted in northern parts of California and the Sierra Nevada Mountains, where the fly exists on its native host, bitter cherry [Prunus emarginata (Douglas) Eaton]. Precipitation of driest quarter, degree days with average temperatures !8.38C, degree days with average temperatures 58C, and mean diurnal range in temperature were the strongest predictors of R. indifferens distribution in western North America. We showed that the predictive power of correlative niche models can be improved by including outputs from the process-based mechanistic niche models. Overall results suggest that R. indifferens is unlikely to establish in the commercial cherry-growing areas in the Central Valley of California, largely because heat stress is too high and chilling requirement in those areas is not met.

Spotted wing drosophila, Drosophila suzukii (Matsumura) (Diptera: Drosophilidae), was monitored from 2010 to 2014 in 314-828 sites located in interior fruit-growing regions of OR and WA, United States, and BC, Canada, using traps baited with apple cider vinegar or sugar-water-yeast. Seasonal population dynamics and sex ratios were summarized for berry, cherry, stone fruit, grape, non-crop host plants, non-host sites, and for conventional IPM, certified organic, backyard, and feral sites, by region and year. Overwintering was detected in all regions and years, despite winter temperatures below -17°C. A spatial analysis was conducted using a Geographic Information System (GIS), daily weather data, geomorphometric measures of terrain, distance to water, and other variables, at each site. Overwintering success at a site, measured as Julian week of first capture of D. suzukii, was significantly related (R2 = 0.49) in cherry habitats to year, agronomic treatment, and number of winter days with temperatures>-5°C. In berry, cherry, stone fruit and grape habitats, 2011-2014, it was significantly related (R2 = 0.42) to year, agronomic treatment, the logarithm of peak population of D. suzukii in the prior autumn, latitude, elevation, and topographic wetness index. The results show that D. suzukii has adapted to exploit a succession of irrigated crops and feral habitats in mixed landscapes of a semi-arid region with cold winters and hot dry summers, and are shaping strategies for pest management and for biological control.

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Native to Asia, the spotted lanternfly, Lycorma delicatula (White), is an emerging pest of many commercially important plants in Korea, Japan, and the United States. Determining its potential distribution is important for proactive measures to protect commercially important commodities. The objective of this study was to assess the establishment risk of L. delicatula globally and in the United States using the ecological niche model MAXENT, with a focus on Washington State (WA), where large fruit industries exist. The MAXENT model predicted highly suitable areas for L. delicatula in Asia, Oceania, South America, North America, Africa, and Europe, but also predicted that tropical habitats are not suitable for its establishment, contrary to published information. Within the United States, the MAXENT model predicted that L. delicatula can establish in most of New England and the mid-Atlantic states, the central United States and the Pacific Coast states, including WA. If introduced, L. delicatula is likely to establish in fruit-growing regions of the Pacific Northwest. The most important environmental variables for predicting the potential distribution of L. delicatula were mean temperature of driest quarter, elevation, degree-days with a lower developmental threshold value of 11°C, isothermality, and precipitation of coldest quarter. Results of this study can be used by regulatory agencies to guide L. delicatula surveys and prioritize management interventions for this pest.