Oregon Forest Pest Detector Field Guide

Brandy Saffell and Amy Grotta
EM 9127 | July 2022 |

About this guide

This publication was developed for Oregon Forest Pest Detectors as a field reference guide.

OFPDs complete an online course and field workshop that prepare them to recognize and report the signs and symptoms of high-priority, invasive forest pests. This guide contains a summary of the highlights from the OFPD training, including quick facts, host species, insect identification, and signs of symptoms for each insect. This guide is meant to be used as a reference in the field to aid in the identification of a potential invasive insect infestation.

Take the online pest detection class

Scale up your ID skills with OSU’s Oregon Forest Pest Detector online training. Engaging, interactive presentations will help you build your detective skills and defend Oregon forests.

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Oregon Forest Pest Detector program


The purpose of the Oregon Forest Pest Detector program is to improve the likelihood of Early Detection and Rapid Response to a possible future introduction of forest pests in Oregon. The Oregon Forest Pest Detector program will assist with EDRR by increasing the number of skilled individuals that can recognize the signs and symptoms of the target pests and report suspected infestations.


Oregon Forest Pest Detectors observe host trees for signs and symptoms of forest pests of concern in the course of their everyday work activities. They often serve as the first point of contact for the public, help filter public reports, and pass along reports of serious concern to state (Oregon Department of Agriculture) and federal (USDA-APHIS) government partners.

Key responsibilities

  • Demonstrate skill in recognizing host trees and target pests by taking the training course, passing the quiz, and taking a short refresher quiz each year.
  • Apply demonstrated skills during the course of regular work or volunteer activities by paying close attention to host trees that exhibit possible signs and symptoms of target pests.
  • Use an agreed-upon reporting mechanism (Oregon Invasive Species Hotline) to alert state and federal government experts in the case of a possible infestation.
  • Upon request and when convenient, follow up on public reports or inquiries.
  • Refrain from publicizing a possible detection until it has been confirmed by an expert from a designated regulatory agency (Oregon Department of Agriculture or USDA-APHIS).
  • Share appropriate public messages about preventing the spread of invasive forest pests (such as Don’t Move Firewood).

Learn more about the OFPD program and sign up for a training.

Emerald ash borer

Quick facts

Agrilus planipennis

  • Invasive wood-boring beetle
  • Originally from Asia; first reported in the United States in 2002 (Detroit, Michigan).
  • Rapidly expanding across the U.S.
  • Attacks and kills ash trees (Fraxinus spp.); kills about 99% of ash trees native to the U.S.
  • Causes major damage to urban and natural forests.

Quick-reference Oregon monitoring calendar

calendar showing stages of development and which form is active when
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Recognizing ash trees

EAB primarily attacks true ash (Fraxinus spp.), but it also attacks white fringetree (Chionanthus virginicus). The white fringetree is not native to Oregon, but it can be found (somewhat rarely) as a street tree in some urban areas.

ash bark with ridges
Canoe-shaped seeds hanging in clusters
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Common ash look-alikes

Walnut, Juglans spp.

Not an EAB host.

  • Alternate branches.
  • Compound leaves with five to 25 leaflets.
  • Large, round, hard-shelled nut with a green husk.
  • Chambered pith.
walnut twig dissected shows chambers in pith
walnut twig in hand

Boxelder, acer negundo

Not an EAB host.

  • Opposite branches.
  • Compound leaves with three to five leaflets.
  • Paired samaras.
  • Mature bark is light gray and not deeply furrowed.
Boxelder seeds
boxelder leaves

Mountain ash, Sorbus spp.

Not an EAB host.

  • Large shrub or multi-stemmed tree.
  • Alternate branches.
  • Red berries in clusters.
  • Mature bark is light gray and smooth.
Mountain ash leaves and berries
shrub form of mountain ash

Note on Oregon ash

Oregon ash is a riparian species that is ubiquitous in wetlands throughout northern California and western Oregon and Washington. It often looks unhealthy even in its natural, native environment. It is not uncommon to see stands of Oregon ash with leaf blight (1) as well as crown dieback (2) and epicormic branches (3). These symptoms could easily be mistaken for an EAB attack. If you see crown dieback or epicormic branches on Oregon ash in a natural setting, do not feel obligated to check every tree with these symptoms for EAB. Instead, monitor the stand and spot-check for further signs of an EAB infestation.

browning at ends of ash leaves
ash defoliation
shoots emerging from tree trunks
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Identifying emerald ash borer

  • Metallic green body.
  • Coppery-red highlights and abdomen.
  • ¼ to ½ inch long.
  • Narrow, bullet-shaped body compared to other metallic green, native insects.
emerald ash borer adult
emerald ash borer viewed from the top
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Common EAB look-alikes

other insects resembling the emerald ash borer
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EAB larvae

  • About 3 cm long.
  • Bell-shaped segments.
  • Flat and tapeworm-like in appearance.

Note: If you find what looks like an EAB larva in a tree, make sure it is an ash tree.

white worm with ridges
ridged white worms adjacent to metric ruler

EAB galleries

  • S-shaped.
  • Below bark. (Larvae only feed on phloem. They do not burrow deeply into the tree.)
  • One of the first noticeable indicators of an infestation.
  • Bark-splitting often reveals S-shaped galleries.
zigzagging white lines below layer of bark
s-shaped lines in wood
crack in bark
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EAB signs and symptoms

Woodpecker damage

  • Mottled, blonding appearance.
  • Bark flaked away (not deeply excavated).
  • One of the first noticeable indicators of an infestation.
bark has been flaked away from tree trunk
flaky bark

Epicormic branches

  • Branch sprouting from bark.
  • Can be found anywhere along trunk.
  • Often appear in late stages of infestation.

Crown dieback

  • Top third of crown.
  • May not be noticeable until tree is heavily infested.
crown thinning
thinning leaves at crown

EAB exit holes

  • Adult emergence holes.
  • D-shaped.
  • About 3mm across (⅛ inch).
D-shaped hole in bark with pencil for scale
small round holes with penny for scale
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EAB reporting decision tree No. 1

You see an unhealthy tree with woodpecker damage, crown dieback or epicormic shoots.

submit a report if the ash tree is in a natural area, notice damage or disease and shows other signs and symptoms, such as D-shaped exit holes or galleries
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EAB reporting decision tree No. 2

You see an insect that looks like EAB.

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Asian longhorned beetle, Anoplophora glabripennis

Quick facts

  • Invasive wood-boring beetle
  • From Asia; first reported in the United States in 1996 (Brooklyn, New York).
  • Has been introduced to several other U.S. states and Canadian provinces.
  • Attacks 12 genera of hardwood hosts, primarily maple (Acer spp.).
  • Loss of 30% to 70% of tree canopy.
  • Causes major damage to urban and natural forests.

Quick-reference Oregon monitoring calendar

calendar showing stages of insect and times of activity
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ALB host species

Maple, Acer spp.

  • Opposite branches.
  • Simple, palmate leaf.
  • Paired samaras.
  • Includes boxelder.
maple leaves
maple samaras or seeds
maple samara in palm

Birch, Betula spp.

  • Alternate branches.
  • Simple, serrate leaf.
  • Deciduous catkin.
  • Mature bark is often white or pink to gray to brown.
birch leaves and cones
birch bark and fingers
birch bark, peeling

Elm, Ulmus spp.

  • Alternate branches.
  • Simple, egg-shaped, serrate leaf.
  • Round samara.
  • Mature bark often deeply furrowed.
elm leaves
elm seeds green fan shape with tip

Willow, Salix spp.

  • Alternate branches.
  • Long, narrow leaf.
  • Catkin with cotton-like seeds.
willow leaves long and pointy
willow catkin long fluffy white
willow twig

Horse chestnut, Aesculus hippocastanum

  • Opposite branches.
  • Compound leaf with five to 11 leaflets.
  • Green, spiny fruit.
  • Mature bark smooth to flakey, sometimes plated.
horse chestnut leaves and flowers
spiny round green balls
brown pit at heart of fruit

Other hosts

  • Ash (Fraxinus)
  • Poplar (Populus)
  • Sycamore (Platanus)
  • Mountain-ash (Sorbus)
  • Mimosa (Albizia)
  • Katsura (Cercidiphyllum)
  • Golden raintree (Koelreuteria)
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Identifying ALB

  • Shiny, black body with white spots,
  • Long antennae with white bands,
  • Six legs.
  • 2 to 34⁄5 cm without antennae (about ¾ to 1½ inches).
  • May have bluish feet.
two white wormlike larvae
beetle larvae mouth parts
asian longhorned beetle

ALB galleries and tunnels

  • Larvae tunnel deep into trunk and branches.
  • Not immediately visible early in an infestation.
tunnel chambers in wood
alb tunnels from top
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ALB look-alikes

variety of insects that resemble asian longhorned beetle

Carpenterworm moth larvae, Prionoxystus robiniae

  • About 5 to 7½ cm long (2 to 3 inches).
  • Have prolegs. (ALB does not.)
  • Oval-shaped tunnels.
  • Exit holes similar in size to ALB.
white grub with black head

Citrus longhorned beetle, Anoplophora chinensis

  • Length: About 2 to 34⁄5 cm (similar size to ALB).
  • Hosts: 100-plus species; primary hosts include citrus (Citrus), apple (Malus), trifolate orange (Poncirus trifoliata), poplar (Populus), willow (Salix), Australian pine (Casuarina equisetifolia).

Note: This is another high-priority invasive insect. If you think you have found a citrus longhorned beetle, please report it immediately.

citrus longhorned beetle

ALB signs and symptoms

ALB exit holes

  • Round
  • 1 cm (⅔ inch) across
  • Found on branches, trunk, and above-ground roots
hole smaller than a dime

ALB egg scars

  • Also referred to as oviposition sites or pits.
  • Egg-laying site.
  • 1 cm (⅔ inch) across.
  • Sap can sometimes be seen weeping from egg scar.
finger pointing to indentation in bark
finger pointing to scrape in bark
scrape on bark filled with brown grass


This stringy sawdust substance (excrement) may be found on the ground, in tree branch unions or coming out of holes on living branches.

brown shavings in crook of trunk
brown shavings

Crown dieback and broken branches

These symptoms may not be noticeable until tree is heavily infested.

large gaps in crown of tree
broken branches in crown of tree
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ALB reporting decision tree No. 1

You see a tree that seems unhealthy. It has holes in it, the crown is dying back and branches are breaking.

If the tree is one of the ALB host species, look for other causes. If you see round holes or frass submit a report.
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ALB reporting decision tree No. 2

Here's what to do if you see an insect that looks like the Asian longhorned beetle.

Capture the insect and compare with ALB look-alikes. File a report if you think you have an ALB.
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Reporting protocol

1. Record the following:

  • Site location and description (GPS coordinates or map, natural or urban area, public or private).
  • Signs and symptoms observed (including host tree species).
  • High-quality, well-lit photos of damage or insects. Include an object for scale.

2. Collect samples:

  • Put wood or frass into a labelled plastic bag. Double-bag so nothing can chew out and escape in transit.
  • Put insects into a clear, hard container (such as a glass vial or plastic food container). Preserve in a freezer or in rubbing alcohol.

3. Go to the Oregon Invasive Species Hotline:

  • Select report now and complete a report.
  • Be as detailed as possible.
  • Provide your contact information so an expert can follow up.

Confidentiality agreement

If an ALB or EAB infestation is suspected, it must remain confidential until it is verified by professionals and the information is made public by the appropriate authority. Reports made to the Oregon Invasive Species Hotline will remain confidential. As an Oregon Forest Pest Detector, you must agree to protect information and suspected pest name, location and identity of any property owner or individual associated with the infestation until the proper authorities have released this information publicly.

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Funding provided by USDA-APHIS and the USDA Forest Service.

  • Robbie Flowers, USDA Forest Service
  • Mark Hitchcox, USDA APHIS
  • Jennifer Killian, Friends of Trees
  • Jim LaBonte, Oregon Department of Agriculture
  • Paul Oester, OSU Extension Service
  • Kristin Ramstad, Oregon Department of Forestry
  • Helmuth Rogg, Oregon Department of Agriculture
  • Dave Shaw, OSU Extension Service
  • Tania Siemens, Oregon Sea Grant
  • Wyatt Williams, Oregon Department of Forestry

About the authors

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