Forest Health Advisory
Background
America’s forests provide ecological, social, and economic services to our Nation. An important aspect of maintaining and enhancing a healthy forest is to protect and restore forests from insects and diseases that cause high levels of tree decline and mortality.
The US Forest Service conducted the 2013-2027 National Insect and Disease Forest Risk Assessment to provide a nationwide summary of the potential susceptibility to tree mortality caused by major forest pests. Results for North Dakota are presented below to inform assessments of natural ecosystems and prioritize potential management for pest prevention, suppression, and restoration.
Since 2012, major tree mortality events from forest pest outbreaks, fire, and broad scale forest harvesting operations have reduced or in some cases eliminated risk*. To account for this, areas where significant tree mortality events have occurred have been removed. These areas are represented in the map below as ‘Disturbances/treatments in risk areas’. However, many areas still remain highly susceptible to future mortality - ‘Remaining Risk’ in the map below. A major tree mortality event was defined as one or more of the following:
- Areas depicted as forest cover loss in the University of Maryland Global Forest Change dataset.
- Three or more years of mortality mapped in aerial detection surveys (ADS; Insect and Disease Survey database).
- In the Eastern U.S. only, three or more consecutive years of defoliation mapped in ADS.
Note: The 2018 update does not account for increases in risk due to recent tree growth and density, which can make additional trees susceptible and vulnerable to new forest pest attacks.
This advisory is designed to raise awareness about forest health concerns and provide common ground for consultation between resource managers and forest health specialists. Impacts summarized below assume no active management during a 15-year (2013-2027) time frame.
*Risk, or more appropriately termed hazard, is defined as the expectation that, without remediation, at least 25% of standing live basal area greater than one inch in diameter will die over a 15-year time frame (2013 to 2027) due to insects and diseases.
What is at Risk and What are the Threats for North Dakota?
Within North Dakota, 89,440 acres are susceptible to high levels (≥25%) of overall tree mortality, and 10% of the tree biomass is at risk to forest pests. Accounting for major forest disturbances, such as insect and disease outbreaks, fires, and treatments, the remaining area at risk is now 89,399 acres, representing a reduction of <1%. This reduction in risk does not account for any increases due to tree growth. Note, the tables below have not been updated to account for this reduction in risk.
| Host Tree Species | Loss, % of Host | Loss, % of All Trees |
|---|---|---|
| American Elm | 29% | 1% |
| Ash spp. | 18% | 6% |
| Aspen spp. | 16% | 2% |
| Cottonwood spp. | 8% | <1% |
| Bur Oak | 7% | 1% |
| Ponderosa Pine | 6% | <1% |
| Tree Species | Prevalence, % of All Trees |
|---|---|
| Green Ash | 30% |
| Bur Oak | 22% |
| Quaking Aspen | 21% |
| Rocky Mountain Juniper | 7% |
| Boxelder | 6% |
| American Elm | 6% |
| Siberian Elm | 2% |
| Black Ash | 2% |
| American Basswood | 2% |
| Forest Pest | Loss, % of Host | Loss, % of All Trees |
|---|---|---|
| Dutch Elm Disease | 31% | 1% |
| Emerald Ash Borer | 18% | 6% |
| Forest Tent Caterpillar | 10% | 1% |
| Oak Decline and Spongy Moth | 7% | 1% |
| Aspen and Cottonwood Decline | 6% | 1% |
| Root Disease(s) – Unspecified | 3% | <1% |
| Bur Oak Blight | 3% | <1% |
| ALL FOREST PESTS | 10% |
| Forest Pest | Host Tree Species |
|---|---|
| Mountain Pine Beetle | Ponderosa pine |
| Forest Tent Caterpillar | Aspen spp. |
| Emerald Ash Borer | Ash spp. |
| Root Disease(s) – Unspecified | Ponderosa pine |
| Aspen and Cottonwood Decline | Cottonwood spp., quaking aspen |
| Dutch Elm Disease | American elm |
| Bur Oak Blight | Bur oak |
Interactive Maps
Potential Management Strategies & Key Contacts
| STRATEGY | Aspen and Cottonwood Decline | Bur Oak Blight | Dutch Elm Disease | Emerald Ash Borer | Forest Tent Caterpillar | Oak Decline and Spongy Moth | Root Disease(s) – Unspecified |
|---|---|---|---|---|---|---|---|
| Detection & Monitoring - Can prevent a pest from increasing to damaging levels and reduce tree mortality, when early detection is followed by a rapid response | |||||||
| Monitor for population fluctuation, establishment, range expansion - traps, aerial/ground survey | x | x | x | x | x | x | x |
| Prevention - Making forests more resilient and reducing pest hazard | |||||||
| Increase species diversity - planting, seeding, tree removal, etc. | x | x | x | x | |||
| Limit movement of firewood | x | x | x | ||||
| Manage age class/stand structure, Increase age class diversity - planting, tree removal, etc. | x | x | x | ||||
| Preventive pesticide treatments | x | x | |||||
| Reduce susceptible species and unhealthy trees | x | x | x | x | |||
| Restoration - Re-establishing processes necessary to facilitate forest sustainability, resilience, and health | |||||||
| Genetic improvement and conservation | x | x | |||||
| Reforestation - replant existing or alternative native species or silvicultural systems that promote natural regeneration | x | x | x | x | x | ||
| Salvage and dead (hazard) tree removal | x | x | x | x | x | ||
| Prescribed burning | x | ||||||
| Suppression - Reduce the overall damage to forest resources from outbreaks of insect and disease-causing pests | |||||||
| Pesticide and biocontrol application | x | x | x | x | |||
| Sanitation - removing, cutting and treating/pruning infested trees/ remove/treat blow down or slash | x | x | x | ||||
| Removal of all host trees | x | x | |||||