This document is an update to the previous risk analysis that was produced on August 9, 2017, to help inform decision makers of the spread potential of Diorhabda beetles and the potential control options available within the authority of APHIS to limit impacts to the SWFL and designated critical habitat. APHIS updated the analysis in response to a remedial order from the United States District Court for the District of Nevada on June 19, 2018.


This version contains the following changes: 1) the APHIS Diorhabda spread model was updated with 2017 detection data and its efficacy was evaluated, 2) recent research on beetle herding using new Diorhabda aggregation and repellent pheromones was added, 3) recent research on modeling tamarisk distribution, southwestern willow flycatcher (SWFL) abundance and habitat occurrence, associated Diorhabda interactions, and the effects of controls and ecological events on SWFL populations was added, and 4) additional knowledge gaps and research needs have been added.