Nonnative forest insects and pathogens in the United States: Impacts and policy options

Abstract

We review and synthesize information on invasions of nonnative forest insects and diseases in the United States, including their ecological and economic impacts, pathways of arrival, distribution within the United States, and policy options for reducing future invasions. Nonnative insects have accumulated in United States forests at a rate of ~2.5 per yr over the last 150 yr. Currently the two major pathways of introduction are importation of live plants and wood packing material such as pallets and crates. Introduced insects and diseases occur in forests and cities throughout the United States, and the problem is particularly severe in the N ortheast and U pper M idwest. Nonnative forest pests are the only disturbance agent that has effectively eliminated entire tree species or genera from United States forests within decades. The resulting shift in forest structure and species composition alters ecosystem functions such as productivity, nutrient cycling, and wildlife habitat. In urban and suburban areas, loss of trees from streets, yards, and parks affects aesthetics, property values, shading, stormwater runoff, and human health. The economic damage from nonnative pests is not yet fully known, but is likely in the billions of dollars per year, with the majority of this economic burden borne by municipalities and residential property owners. Current policies for preventing introductions are having positive effects but are insufficient to reduce the influx of pests in the face of burgeoning global trade. Options are available to strengthen the defenses against pest arrival and establishment, including measures taken in the exporting country prior to shipment, measures to ensure clean shipments of plants and wood products, inspections at ports of entry, and post‐entry measures such as quarantines, surveillance, and eradication programs. Improved data collection procedures for inspections, greater data accessibility, and better reporting would support better evaluation of policy effectiveness. Lack of additional action places the nation, local municipalities, and property owners at high risk of further damaging and costly invasions. Adopting stronger policies to reduce establishments of new forest insects and diseases would shift the major costs of control to the source and alleviate the economic burden now borne by homeowners and municipalities.

Near-Real-Time Monitoring of Insect Defoliation Using Landsat Time Series

“…A growing number of introduced insects and pathogens threaten the health of forested ecosystems across North America, often with significant ecological and economic consequences [1][2][3][4]. Detecting and managing emerging outbreaks and predicting where outbreaks will occur in the future requires up-to-date spatially explicit information on the magnitude and extent of pest and disease impacts [5].…”

Effects of Host Variability on the Spread of Invasive Forest Diseases

“…The current rate of non-indigenous species movement, resulting from human mediated intervention, is unprecedented [1], and has been the main accelerator driving the increase in novel encounters between host plants and pathogens, and the probability of invasive species emergence [2]. Biosecurity policies adopted by most countries for preventing new introductions (e.g., inspections at ports of entry, phytosanitary certification) can have positive effects, but, unless efforts are further strengthened and better coordinated internationally, biological invasions will inevitably continue [3].…”

Economics of invasive species policy and management

“…For example, beneficiaries of imported goods often are not the same entities that incur costs from invasions resulting from those imports (Lovett et al 2016). A forest owners association evaluating implementation of an early detection surveillance system for new invaders may not take into account the benefits of that system to city dwellers whose urban trees also would benefit from the system (Epanchin-Niell et al 2014).…”