Module 1 – Introduction

Learning Objectives

  • To understand what tree and forest health is and why forest health is important.
  • To understand what an invasive species is.
  • To become familiar with the spread and impacts of invasive species.
  • To learn how to collect specimens and report potential invasive species.
  • To become familiar with the vocabulary of forest health and invasive species.

What is forest health and why is it important?

The health of forests and trees is important for many reasons and can mean many things to different people in different situations. The most widely used definitions of forest health tend to incorporate two aspects:

  • The forest’s ability to sustain unique species composition and processes, and
  • The forest’s ability to accommodate present and future needs for a variety of values, products, and services.

Included within those aspects is the forest’s ability to renew itself and be resilient against disturbances.

All forests experience disturbances. Disturbances are any activity that disrupts forests; injures, weakens, or kills trees; or changes the structure or composition of the ecosystem. Disturbances are natural and necessary in forests. Disturbances allow forests to renew, return nutrients to the soil, and can provide important habitat for wildlife. Types of disturbance can include:

  • insect activity,
  • disease-causing pathogens,
  • fire,
  • weather or climate events,
  • animal activity, and
  • human activity, among others.

While some disturbance is natural and is part of a healthy forest, too much disturbance or changes in frequency, timing, or severity of disturbances can have negative impacts on our views of healthy trees and healthy forests.

In Alaskan forests, insect outbreaks, pathogens, wind events, and fires are common disturbance types. These disturbances can be normal and healthy in the forests; however, large-scale events such as the spruce beetle outbreak of the 1990’s on the Kenai Peninsula and the Copper River Valley, can be devastating.

1470173_A Steven Munson_USDA Forest Service_Bugwood org

Steven Munson, USDA Forest Service

9001100-Doug Page_USFS-BLM_Bugwood org

Doug Page, US Forest Service – BLM

1370005_Milan Zubrik_Forest Research Institute-Slovakia_Bugwood org

Milan Zubrik, Forest Research Institute Slovakia

 Invasive species are also disturbance agents in our forests and urban trees and can be devastating for forest health since invasive species pose challenges that native pests do not.

What is an invasive species?

An invasive species is a species that is not native to the ecosystem and whose introduction causes or is likely to cause economic or environmental harm or harm to human, animal, or plant health (Executive Order 13112). Invasive species have the potential to establish and spread in new environments for a variety of reasons.

>> Video 1 (13:55-17:47) <<

This video explains why invasive species are successful and how they can impact the environment.

Invasive species can be transported to new areas in many different ways. Often invasive species are first brought to the country through the shipment of goods. Invasive forest pests can travel to new locations in living plants for the plant trade, wood packaging material including crates and pallets, and as general hitchhikers on a variety of items.

5461415-Joseph LaForest_University of Georgia_Bugwood org

Joseph LaForest, University of Georgia

5252044-Joseph OBrien_USDA Forest Service_Bugwood org

Joseph O’Brien, USDA Forest Service

5476178-USDA Forest Service Southern Research Station_USDA Forest Service_SRS_Bugwood org

USDA Forest Service Southern Research Station

Once established in the country, firewood is a common way that invasive forest pests can be moved to new locations. Firewood can harbor different life stages of pests under the bark or within the wood where they are difficult to detect. Insect eggs can also be present on firewood and go undetected. If unburned firewood is left in a new location, the pests may have the opportunity to complete their lifecycle and emerge to infest nearby trees.

Invasive species can also spread naturally. Invasive plants have seed dispersal mechanisms that contribute to natural spread, and pathogens such as fungi can utilize wind and water to spread their spores. Insects are particularly well suited for natural spread since many of them can fly or otherwise crawl to new locations.

We have been moving people and goods for a very long time, why are invasive species so threatening now? Invasive species have always been threatening. We are still dealing with the consequences of several historical invasions in our forests such as European gypsy moth, Dutch elm disease, and chestnut blight. What makes current conditions unique is that we are now able to move more goods more quickly. Meaning the insects, etc. that accompany the goods are more likely to survive the journey than they were in years past.

How do we monitor for and manage invasive species?


The primary goal of any invasive species program is to prevent the pest from reaching and establishing in a new area. Prevention is accomplished in several ways:

  • border inspections: inspecting goods before they pass between jurisdictions
  • best practices: developing and implementing practical best practices for industries that might be involved in a pathway for invasive species introduction (Ex: vegetation mowing protocols for weeds near roadways)
  • limiting or encouraging limits on movement of goods/pathways: regulatory statutes such as quarantines that legally limit or prevent the movement of goods into or out of an area or social programs that encourage people to do their part to help prevent the spread of invasive species (Ex: don’t move firewood, don’t move a mussel)
Early detection and rapid response (EDRR) is both a specific program and a general strategy for invasive species detection and response. Second only to prevention as an invasive species strategy, EDRR programs seek to:

  1. Detect invaders before they have a chance to establish in a new area and
  2. Assess and respond to the detection rapidly to prevent spread and minimize the amount of damage done

Most EDRR programs rely on active trapping or scouting for invasive species. Several trapping programs occur throughout Alaska for terrestrial and aquatic invasive species. Forest pests commonly trapped for as a part of EDRR programs include defoliating moths and bark beetles and wood borers. Trapping programs allow managers to “look’ for several invasive species at the same time in various locations throughout the state. For more information about Early Detection and Rapid Response (EDRR) see this writeup.

Citizen scientists can also play an important role as first detectors in the early detection of invasive species. Not all pests can be trapped for in all areas so reports from the public and natural resource professionals are important avenues for early detection of potential invasive species. Several detections of invasive species have been the result of reports from concerned landowners.

Eradicating invasive species can be a viable option if the species is detected quickly and has not spread very far, though it still may take several years and several control strategies to complete. In some instances the costs and benefits of eradication need to be weighed very heavily as it is not always practical or possible.

depicting at what stage of invasion or the extent of the infestation/establishment to determine if eradication is a reasonable option or not (or similar)

Figure depicting at what stage of invasion or the extent of the infestation/establishment to determine if eradication is a reasonable option or not (or similar)

If eradication is not possible, or eradication efforts have not been successful and the pest has spread outside of a manageable area, other management options need to be considered. Efforts to contain the pest and slow its spread to neighboring areas should be initiated. Other management options might look at long-term strategies that minimize the impact from the invasive species such as biological control agents, or practices that make the area a less favorable habitat.
Public outreach
Public outreach is a critical tool in any invasive species program. Outreach programs function at every level from prevention to management. Numerous outreach and education campaigns to raise awareness about invasive species have been launched in recent years resulting in a much more informed and engaged public.

Invasive insect pests of trees

We have many species of insects that are native to Alaska and can cause varying degrees of tree damage in our forests. For more information on native and established pests of trees in Alaska see: Insects and Diseases of Alaskan Forests.

The focus of the remaining modules will be on three groups of insect pests of trees. The modules will highlight potential invasive species that are not native or present in Alaska but that have the potential to be damaging if they were to be introduced. These groups are:

Wood boring insects

Wood boring insects bore into the sapwood and sometimes heartwood of trees and shrubs. Wood boring insects usually attack weakened, dead, or dying trees; however, some potential invasive species will attack otherwise healthy trees.

1199010-Steven Katovich_USDA Forest Service_Bugwood org

wood borer damage, Steven Katovich, USDA Forest Service

1457025-Steven Katovich_USDA Forest Service_Bugwood org_2

wood borer damage, Steven Katovich, USDA Forest Service

Bark beetles

Bark beetles live and feed between the bark and the wood of trees and shrubs. This feeding can be very damaging because it disrupts the tree’s ability to feed itself. Additionally, many bark beetles carry fungi that can further compromise a tree’s ability to transport water and nutrients.

0805011-Edward H Holsten_USDA Forest Service_Bugwood org2  0805014-Edward H Holsten_USDA Forest Service_Bugwood org

Defoliating moths

The larvae of some moths feed on the leaves or needles of trees to such an extent that it weakens, or in extreme cases, kills the trees. These insects are referred to as defoliating moths.

Michael Rasy_arctic valley rd defoliation

Reporting information and submitting specimens

Modules 2, 3, and 4 will go over the groups of potential invasive insects in more detail, including identification information and what signs and symptoms to look for. If you encounter a specimen or suspicious damage, here’s how to collect it and/or report it.

If you observe an insect damaging a tree and cannot identify it as one of our native species, it is best to collect the specimen and submit it for identification.

Insect specimens, while somewhat sturdy, are still fairly fragile and should be treated with care. Live insects should be killed before submitting them. Insects can be killed by placing them in the freezer for a night or two or by drowning them in alcohol (70% rubbing alcohol will work). Insects can then be placed in a tightly sealed, sturdy container and brought or mailed to your local Cooperative Extension office (link to map of office locations/contact information).

>>PDF of all this information to link back to<<

Please group specimens by the location/tree from which they were collected. Do not put specimens from different locations in the same container. Please include collection information with each container submitted.

An important aspect of insect specimens that people often forget is the importance of collection information. When you collect a specimen, please make note of the following data:

  1. Location information — Country, state, location
  2. Latitude/Longitude — If possible collect this with a GPS unit and include +/- accuracy. If you do not use a GPS unit, a physical address is second best.
  3. Habitat description, host plant, collection method used (e.g. hand collected, sweep net, trap)
  4. Date and collector — Abbreviate date with letters not numbers to avoid confusion.


  1.      USA: Alaska: Anchorage
  2.        61.205825, -149.88631 +/- 10m
  3.        Ornamental landscape, lilac shrub, hand collected
  4.        13JUL 2015 M.J. Moan

If you do not find any insects, photos of suspicious damage are also welcome! Photos can be submitted through our Pest Portal or to

Digital photos can be great tools for insect identifications. Keep in mind, though, that photos are not without their limitations. The tips below can help improve the likelihood of getting an accurate and quick diagnosis when submitting digital photos.

  • Check photos for clarity before submitting
  • Submit original, unedited photos
  • Include a size reference in your photo (coins and pencils/pens work great if you don’t have a ruler available)
  • Include as much information about the subject as possible
  • Include the same collection information as if you were submitting a physical specimen


  1. Trees and forests are healthy when they can sustain their unique species composition and processes and accommodate a variety of values, products, and services.
  2. Forest health is important because forests and trees provide many benefits ecologically, environmentally, and economically.
  3. An invasive species is a species that is not native to an area and is causing harm.
  4. Invasive species can be spread by the movement of goods and people to new areas.
  5. Invasive species threaten natural ecosystems by outcompeting native species, feeding on native species, and decreasing biodiversity.
  6. Insect specimens can be collected and reported to:
  8. UAF-CES Pest Portal


  1. Bark beetle: A type of beetle that lives and feeds between the bark and the wood of trees and shrubs
  2. Defoliating moth: A moth whose larvae feed on the leaves or needles of trees and shrubs
  3. Disturbance: any activity that disrupts forests; injures, weakens, or kills trees; or changes the structure or composition of the ecosystem
  4. Ecosystem services: A positive benefit that ecosystems provide, such as drinking water, timber, and erosion control.
  5. Forest health: the forest’s ability to sustain unique species composition and processes and accommodate present and future needs for a variety of values, products, and services
  6. Invasive species: a species that is non-native to the ecosystem and whose introduction causes or is likely to cause economic or environmental harm or harm to human, animal, or plant health
  7. Natural enemy: living organism found in nature that kills or weakens its prey or reduces its reproductive potential
  8. Niche: the role a species has in its environment
  9. Non-native/non-indigenous: any organism living outside of captivity or cultivation that did not historically occur in that area
  10. Pathway: the means and routes by which invasive species are imported or introduced into new environments
  11. Wood borer: An insect that bores into the sapwood and sometimes heartwood of trees and shrubs

Sources and More Information

  1. Invasive species. National Wildlife Federation. Last accessed February 8, 2016, from
  2. Why are invasive alien species a problem? July 19, 2013. Environment and Climate Change Canada. Last accessed February 8, 2016, from
  3. Invasive species. February 15, 2011. International Union for Conservation of Nature. Last accessed February 8, 2016, from
  4. Frequently Asked Questions. Hungry Pests. Last accessed February 8, 2016, from
  5. Invasive species. April 29, 2015. U.S. Forest servie — Pacific Northwest Research Station. Last accessed February 8, 2016, from
  6. Committee, I. June 11, 2014. Arctic boreal forest environments. Last accessed February 8, 2016, from
  7. Invasive Species Def: Executive Order 13112