Submitted to: Ecosphere
Publication Type: Peer reviewed journal
Publication Acceptance Date: 4/18/2014
Publication Date: 7/31/2014
Citation: Kumar, S., Neven, L.G., Yee, W.L. 2014. Evaluating correlative and mechanistic niche models for assessing the risk of pest establishment. Ecosphere. 5(7):86. Interpretive Summary: Western cherry fruit fly is an important pest of sweet cherries in the Pacific Northwest of the United States and is the subject of quarantine restrictions to exported sweet cherries. Scientists at the USDA-ARS Yakima Agricultural Research Laboratory and the Natural Resource Ecology Laboratory at Colorado State University determined the potential of western cherry fruit fly in sweet cherries to complete development and establishment under environmental conditions present in the commercial sweet cherry growing region in California. They found that there is a very low potential for this pest to establish and spread in the region. This information may be used to clarify needs for quarantine restrictions for interstate shipment of sweet cherries from the Pacific Northwest to California.
Technical Abstract: Ecological niche modeling was used to assess the risk of establishment of western cherry fruit fly, Rhagoletis indifferens Curran (Diptera: Tephritidae), in sweet cherry, Prunus avium (L.) L., in the commercial cherry-growing areas of California. We integrated species occurrence records and spatial environmental variables using the Maxent (i.e., maximum entropy) niche modeling algorithm to assess the potential risk of establishment of R. indifferens. Maxent model performance was high, with a mean test area under the ROC (receiver operating characteristic) curve value (AUC) of 0.92 and a highly significant correlation between observed presence-(pseudo) absence and predicted probability of presence. The model predicted a very low risk for R. indifferens establishment in the San Joaquin Valley around the areas where sweet cherries are produced. 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 in association with its native host, bitter cherry [Prunus emarginata (Douglas) Eaton]. Human footprint index (a surrogate for irrigation-supported cherry orchards), minimum temperature of coldest month, temperature annual range, and precipitation seasonality were the top predictors of R. indifferens distribution. Overall results suggest that R. indifferens is unlikely to establish in the commercial cherry-growing areas in the San Joaquin Valley of California, largely because chilling requirements in those areas are not met.