The Hemlock Woolly Adelgid Event Monitor is a program that simulates the effects of the hemlock woolly adelgid (Adelges tsugae) within the confines of the Forest Vegetation Simulator (FVS). Infestation date is provided by the user, based on knowledge of the stand, and published estimates of population movement and projected infestation date. Once infestation occurs, mortality is leveled against eastern and Carolina hemlock species at the end of the FVS cycle. Hemlock woolly adelgid induced tree mortality is determined by the intensity of the initial infestation and the subsequent adelgid population cycles. Impact is also mediated by the geographic location of the stand, with relative impact on hemlock mortality increasing for southern hemlock stands.
This is a strategic model that demonstrates the potential loss of hemlock timber and habitat due to hemlock decline and mortality. The user can proactively reduce the risk posed by the hemlock woolly adelgid by scheduling appropriate management actions within FVS such as thinning to remove hemlock. Once an event is scheduled by the Hemlock Woolly Adelgid Event Monitor there are no reactive measures the user can take to prevent the loss of hemlocks or remove infestations.
Users of the Hemlock Woolly Adelgid Event Monitor should also be aware that, due to the limitations in FVS’s growth and mortality equations, the inter-tree variability normally seen in response to infestation by the hemlock woolly adelgid cannot be adequately modeled. Because of this limitation, the user is cautioned that this Event Monitor is best suited for evaluating relative differences in adelgid infestation at the stand level, rather than absolute responses for specific stands.