Early detection of Asian Longhorned Beetle (ALB) infestations in North America is critical to the overall success of eradication programs both in terms of time and money. This module will highlight what you should look for in detecting ALB 1
This image shows two types of wounds created on tree stems by Asian Longhorned Beetle (ALB): adult emergence holes and oviposition pits. Both of these wounds can occur anywhere on the tree; from the uppermost portion of the canopy to "eye-level" on the main trunk. 1) Adult emergence holes are created by adult beetles as they emerge from trees: a) Two of the emergence holes remain open; the tree has not responded to the wound by creating callus (wound) tissue to close the wound. b) The hole labeled "Old-Closing" is an emergence hole that is being closed by the tree's response to the wound; it's being closed by callus (wound) tissue. This hole was probably created some weeks ago; it would be completely closed if it was created last season. 2) Oviposition (ovi- = egg) pits were created when ALB females chewed through the bark, phloem, and cambium to deposit a single egg on the surface of the xylem (wood). a) The pit labeled "New" is very recent, probably within a few days. The phloem tissue around the edge of the pits rapidly turns dark because of oxidation. b) The pit labeled "Old-Weeping" was created several days ago; perhaps over a week ago. Older pits may ooze sap any time during the growing season; this image was taken in early September. However, this symptom does not always occur and it is most evident on smooth bark. c) The pit labeled "Old-Closing" has been closed by the tree's response to the wound; it's being close by callus (wound) tissue. This pit was probably created over a month ago. Those that were created last season are often so completely closed they may be difficult to detect, particularly on rough bark. NOTE: the speed with which trees close adult emergence holes and female oviposition pits depends upon several factors including overall tree health, the age of the tree, and the level of the ALB infestation. In general, wound closure occurs much more rapidly on young healthy trees compared to older "over mature" trees. Closure occurs more rapidly on lightly infested trees compared to trees that are heavily infested and seriously damaged by ALB. 2
1) First Image: a) ALB adults create perfectly circular holes as they emerge. b) Adult ALB range in size (whether from different states, different climates, different host trees, etc.) and thus their exit holes range in size regardless of if they are male or female. Some references compare emergence holes to being about the size of a dime, which is really to say exit holes are smaller than a dime; the reference is to help the public visualize the holes. c) The circled area shows a flap of bark covering a future adult emergence hole. ALB larvae will tunnel almost to the surface before pupating; they often leave behind a thin layer of bark covering the tunnel exit to aid in their emergence as an adult. d) ALB adult emergence holes can occur anywhere on the tree; from the uppermost portion of the canopy, to "eye-level" on the main trunk, down the soil line on the trunk flare. 2) Second Image: Shows an adult that is just emerging. If you look closely at the upper left portion of the adult's head, you can see the beetle's mandibles as they are being used to chew a larger diameter hole. 3
1) First Image: the so-called "Pencil Test" demonstrates two things: a) ALB adult emergence holes are usually about the same size or slightly larger than a #2 pencil; so the pencil can be easily inserted into an ALB emergence hole. b) ALB larvae tunnel deep inside the xylem (wood) of the tree which means #2 pencil can usually be inserted deep into the tree. The depth separates xylem feeding borers from phloem feeding borers such as emerald ash borer; a pencil can only be inserted a very short distance (around 1/16") if the emergence hole was made by a phloem feeding borer. 2) Second Image: shows the larval tunnel and subsequent ALB emergence hole extending into the xylem. 3) Third image: demonstrates why a pencil can be inserted into and ALB emergence hole. 4
Since ALB larvae tunnel deep within the xylem (wood) of the tree, woodpeckers must dig deep into the stem in order to extract the larvae. The woodpecker activity leaves behind deep, conical-shaped holes excavated into the wood of the tree. This separates the shallow woodpecker feeding activity associated with phloem feeding borers such as emerald ash borer from woodpecker activity targeting longhorned beetles such as ALB. NOTE: Deep woodpecker holes only indicates the birds were going after a borer larvae located deep within the wood of the tree; it is not a sure sign of an ALB infestation. The borer could be a native species. 5
The Tree Health Continuum and the associated Tree Borer Tree Health Continuum demonstrates that our native borers select live but stressed, dying, or dead trees. That is because those trees are not able to mount a defense against the borers. Defense strategies, both chemical and physical, developed because the native borers co-evolved with their native tree hosts. 6
1) The first image shows a landscape sugar maple in serious decline; note the leaf discoloration and canopy thinning. 2) The second image shows fungal fruiting structures; evidence of interior fungal decay (fungal rot). This indicates the tree is rapidly sliding towards "dead" on the Tree Health Continuum to become fodder for native borers. 3) The third images is a close-up of the fungal fruiting structures growing from the tree. 4) The fourth image shows native beetle borer adult emergence holes. Their size and round shape indicates they were most likely made by a longhorned beetle (Cerambycidae). 5) The final image shows the "Pencil Test" which provides further evidence the borer was most likely a longhorned beetle since the tunnels extend into the xylem. The take-home message is that native borers are not killing this tree; the longhorned beetles were a secondary problem. Tree decline made this maple susceptible to becoming infested by native borers because the tree could no longer defend itself. Native longhorned beetles serve an important ecological function, along with the wood rotting fungus, by initiating tree decomposition. Final Note: this tree was investigated for ALB and it was found that the emergence holes were made by a native longhorned beetle, not ALB. Although these images illustrate ALB look-a-like emergence holes, you should never rule out ALB simply based on the attack occurring on a declining maple. 7
ALB will attack maples in decline; it will not infest dead trees. 7
Oviposition pits are chewed by ALB female beetles to accommodate a single egg per pit. The pits can occur anywhere on the tree; from the uppermost portion of the canopy to "eye-level" on the main trunk. 1) The pit labeled "New" is very recent, probably within a few days. The phloem tissue around the edge of the pits rapidly turns dark because of oxidation. 2) The pit labeled "Old-Weeping" was created several days ago; perhaps over a week ago. a) Older pits may ooze sap any time during the growing season; this image was taken in early September. b) However, this symptom does not always occur and it is most evident on smooth bark. 3) The pit labeled "Old-Closing" has been closed by the tree's response to the wound; it's being close by callus (wound) tissue. This pit was probably created over a month ago. Those that were created last season are often so completely closed they may be difficult to detect, particularly on rough bark. 8
1. The first image on this slide shows an ALB female using her powerful mandibles to chew through the bark, phloem, and cambium to create a pit that stops at the surface of they xylem (wood). a) This female took around 18 minutes to create her pit. b) She then lays a single egg in each pit, so it is called an "Oviposition Pit" (ovi- = egg). 2. The second and third images show the size of the oviposition pits in relation to a U.S. quarter. a) Oviposition pits are most noticeable when they are first chewed by the females and the bark and phloem tissue is freshly exposed. b) Eventually these tissues will darken because of oxidation. 3. The fourth image on this slide shows the bark stripped away from a silver maple to expose the phloem and the oviposition pits chewed through to the xylem. The black tissue is where exposed cambial cells have died. Each pit has a single egg laid onto the darkened surface. 4. Sap may ooze from the pits during season which is helpful in disclosing their presence, particularly on stems with smooth bark. a) Older pits may ooze sap any time during the growing season; this image was taken in early September. b) However, this symptom does not always occur and it is most evident on smooth bark. 5. The final image shows oviposition pits that have been closed by the tree responding to the damage by creating callus (wound) tissue. This may happen quickly with pits being closed by callus tissue within a few weeks. 9
1) The term "frass" applies to insect excrement such as the frass pellets produced by caterpillars as well as refuse generated by insect activity which may contain both plant material as well as excrement. 2) The first image on this slide shows ALB frass that was produced by larval feeding activity as well as ALB females as the excavated oviposition pits. ALB frass is predominantly composed of small slivers of wood; it looks a bit like excelsior (wood wool) used as packing material. 3) The second image shows ALB frass that has collected in a branch fork; a good place to look for frass produced by ALB as well as other tree borers. 4) The third image on this slide shows frass that was produced by an ALB larva prior to pupation; this frass is often pushed out of trees when ALB adults emerge. 5) The fourth image shows the powerful, sharp, almost sickle-shaped mandibles of an ALB adult female. 6) The fifth slide shows an ALB female excavating an oviposition pit. The fine wood particles produced during the excavation contributes to the refuse that is collectively known as frass. NOTE: Finding excelsior-like frass collecting on top of bark plates, in branch forks, or at the base of a tree only indicates that the tree is infested with an insect borer(s). The culprit may be ALB or a native insect borer. However, finding frass on or around a maple that appears healthy should generate closer inspection because ALB will infest healthy trees and maple 10
is a favored host. 10
As noted in Training Module 4, the feeding activity of Asian longhorned beetle larvae can also stimulate meristematic cambial cells to differentiate to form callus tissue. NOTE: research has shown the production of callus tissue in response to tree borer larval feeding activity may be more closely related to tree defense rather than tree wounding. Rapid production of callus tissue can actually crush larvae as the feed on the phloem. The expansion of the lip-like callus tissue can cause the overlaying bark to split or crack open. While this symptom can be caused by Asian longhorned beetle, it can also be produced by the activity of other insect borers as well as a number of other causal agents such as rapid changes in winter temperatures (e.g. freeze-thaw cracking), root damage, exposure to certain herbicides, just to name a few. 11
New ALB infestations have been discovered in the U.S. because of unusually heavy stem breakage! 1) The first image on this slide shows the top of an infested silver maple broken out because of ALB larval tunneling activity. ALB larvae tunnel through the wood (xylem) of the tree seriously reducing structural support. 2) The second image shows a branch that has broken off of a red maple that was infested with ALB. a) Look at the ends of branches that have broken off of LIVE maples for evidence of ALB larval activity including tunneling and frass. b) There are no native longhorned beetles (cerambycids) with larvae that tunnel throughout the wood (xylem) of live maple stems; either the branches or the trunk. NOTE: There are native longhorned beetles that target dying or dead trees or parts of trees such as dying or dead branches. The larvae of these longhorned beetles look very similar to ALB larvae and they tunnel through and feed on the wood of the tree. It's still best to report such findings particularly if they are found on a maple tree. 12
Look at the ends of branches cut from maple trees during pruning! 1) The first image on this slide shows branches cut from a LIVE maple tree that was heavily infested with ALB as is evident by the large numbers of adult emergence holes. a) Note the heavy ALB larval tunneling damage. b) ALB larvae tunnel through and feed on the wood of live trees; maple is a preferred host. 2) The second image is a close-up of the end of one of the branches cut from the infested maple tree showing ALB larval tunneling damage. 13
How Big is ALB? 1) ALB is a huge beetle compared to other beetles found in North America. a) This image shows a female beetle in relation to the size of a U.S. quarter. Although the beetles may range in size, females are usually larger than male beetles. b) Beetles may range in size from 3/4" to 1 1/2 " in length with most being over 1" in length. 2) ALB is called a "Longhorned" beetle because of their long antennae; a characteristic that is shared with other members of the Longhorned Beetle Family, Cerambycidae. 3) ALB Females and males can be distinguished based on the length of their antennae: a) Males have much longer antennae; they are often longer than the length of the beetle's body. b) Females have shorter antennae; they measure less than the length of the body. 14
Key ALB Identification Features 1) ALB antennae have alternating black and bluish-white bands. As the beetles age, the bluish tint may fade which is why ALB is often described as having antennae with alternating black and white bands. 2) Likewise, ALB leg segments have bluish-white markings that also fade with age; older beetles may appear to have black legs. 3) The thorax is solid black with no markings. This is an important distinguishing feature compared to Citrus Longhorned Beetle (Anoplophora chinensis) which is a similar looking, closely related species that is not known to be in North America. Of course, both species should be reported if found. 4) The front wings of beetles are hardened structures that protect the hind wings and abdomen; their proper name is "elytra," but they are also called "wing covers." The wing covers of ALB have randomly arranged, blurred, irregularly-shaped white to creamy-white spots on a shiny black background. One common name for the beetle in its native land of China translates to "starry night beetle." 15
1) ALB adults are often shown on trees. a) Although they are very good fliers, the adults tend to remain on the tree from which they emerged as long as the tree can support the development of a new generation of beetles. b) Part of the reason for ALB adults being slow to take flight is because of the size of the beetles and energy expended during flight. These are huge beetles and they expend a lot of energy during flight; energy the must be recharged by adults feeding once they land. The primary purpose of the adult stage is to reproduce; more time spent feeding means less time accomplishing their primary mission. It also increases adult exposure to enemies. 2) However, adults can and do fly! a) They may take flight when from trees that are no longer a viable food source for the larvae; the tree will not support a new generation. Or, they may take flight when they feel threatened. b) This means ALB adults may appear in unexpected places such as on the side of homes and buildings. c) One of the last ALB adults found in Chicago was strolling along on a sidewalk! 16
1) The first image shows a mature ALB larva that has been extracted from the xylem (wood) of a LIVE maple tree. 2) The second image shows a middle instar ALB larva. 3) The final image shows a mature ALB larvae; mature larvae can measure over 2" long. 4) As with all cerambycid larvae, they have large, rounded segments making them resemble an arm or leg of the Michelin Man. 17
ALB Larvae: A Roundheaded Borer 1) Cerambycid larvae are called "Roundheaded Borers" because of their large, round 1 st thoracic segment; the segment just behind the head. 2) The head is actually partially hidden by the 1 st thoracic segment 18
Be Aware of Native Longhorned Beetles (Roundheaded Borers)! 1) There are many species of native Longhorned Beetles and their larvae (Roundheaded Borers) may look very similar to ALB larvae. 2) This Redheaded Ash Borer larva is a good example. a) Despite this beetle's common name, its larvae may be found in a many of the same host trees as ALB including maple and elm. b) However, the beetles will not target live and healthy trees; the larvae are found in dying or dead trees; they often found in logs and are considered a serious forest products pest. 3) The difficulty with accurately identifying roundheaded borers (cerambycid larvae) based on visual features is the reason that the true identity of ALB larvae the confirmation is based on a DNA analysis. 4) You SHOULD NOT assume that a roundheaded borer that is found in a dying maple tree is probably a native borer! Roundheaded borers found in maple should be investigated. 19
Be Aware of Other Borers that may be found in ALB host trees including maples! 1) There are many species of native borers that may infest ALB host trees. 2) Carpenterworm caterpillars are the larval form of a moth (Prionoxystus robiniae). a) Carpenterworm caterpillars share many of the same host trees with ALB including: maple, elm, willow, cottonwood (poplar), sycamore, and ash. b) They attack live trees. c) Mature carpenterworms can measure over 3" in length. While the caterpillars are usually light green to greenish-white, they may occasionally appear almost cream-colored. d) The caterpillars bore into and feed on the xylem and produce damage that looks almost exactly like ALB larval damage. e) Carpenterworm exit holes are round and only slightly larger than ALB exit holes; the size differences would be hard to distinguish. f) IMPORTANT DIFFERENCES: As with all caterpillars, carpenterworms have three pairs of hardened thoracic legs - the legs on the three segments behind the head - and short prolegs which are the fleshy legs on the abdominal segments. ALB larvae (as with all roundheaded borers) do not have thoracic legs or prolegs. 20
NOTE: Do not ignore round exit holes and large tunnels in the xylem of maple trees even with finding carpenterworm caterpillars. There is always the possibility that carpenterworms are infesting a maple that is also infested with ALB. 20
This slide provides a review of the Key Features you should be aware of for detecting ALB. 21
Ever since ALB was first found in North America in 1996 (in Brooklyn, NY), investigative studies have continued in search of both an ALB chemical attractant as well as effective traps that will capture beetles. First Image: traps that were part of an ALB trap design trial in Ohio in 2015. Second and Third Images: shows research conducted in 2011 in Ohio that investigated both beetle attractants as well as trap designs An effective ALB chemical attractant and a practical trap would be tremendously helpful with finding new ALB infestations as well as with monitoring existing infestations. Unfortunately, no ALB chemical attractant coupled with an effective trap design have been found. NOTE: Research studies are continuing. 22
1) Visual Detection remains the most effective way to discover new ALB infestations in North America and for monitoring existing infestations. 2) Binoculars are very helpful because key ALB detection features such as adult emergence holes and oviposition pits can occur anywhere on a tree; from the uppermost portion of the canopy, to "eye-level" on the main trunk, down the soil line on the trunk flare. 3) This image shows a pair of binoculars that are being used to detect ALB. a) The particular make and model shown here is not important*; there are many manufactures of quality binoculars with specifications that are useful in detecting ALB. These include: Rugged waterproof construction: binoculars intended for wildlife viewing (e.g. hunting or birding) are the best option. No-fog lenses: ALB adults are present throughout the "dog-days" of summer meaning high humidity can be an issue. Medium magnification and good light gathering characteristics. The binoculars shown are 8 X 42: the first number (8) is the magnification and the second number (42) is the size (mm) of the light-gathering lens the objective lens. Medium-range magnification is recommended because high magnification also magnifies shaking and makes inspecting the entire canopy more time consuming; individual stems will fill the binocular view! "Zoom binoculars" may be helpful by allowing users to change magnification (= zoom in and out); however, quality zoom binoculars those that provide sharp imaging throughout the zoom range are expensive. The ability for the binoculars to function under low-light conditions found in forests is important, within reason. While larger lenses gather more light, they also increase weight and make binoculars more cumbersome. 23
* No product discrimination is intended or endorsement by Ohio State University or NPDN is implied. 23
These images show a ground surveyor and a "climber" who work for an ALB Eradication program. Ground surveys are the first step in detecting new infestations and documenting existing infestations including determining the number of infested trees as well as delimiting (= find the outer edge) the infestation. Surveyors working for eradication programs are highly trained and are provided with equipment necessary for documenting infested trees (e.g. measuring trees, geotagging locations, etc.) Highly trained professional tree climbers are called upon when trees are suspected of being infested but the infestation cannot be confirmed by a ground surveyor. This high-risk work should be done by a tree climbing professional; you should not climb trees to look for ALB unless you are a welltrained professional. This can be very dangerous work! 24
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