Asian Longhorned Beetle

Adult Trapping System 

Research Issue

Ways to detect new Asian longhorned beetle (Anoplophora glabripennis) (ALB) infestations, monitor ALB population levels, and verify that eradication has taken place were needed.  Prior to the research reported here, there was no effective way to attract and trap adult ALB.  Monitoring of ALB using ground or tree climbing surveys is labor intensive, highly inefficient, and sometimes ineffective.  The usual approach to monitoring insects was followed to develop pheromone-baited traps because of their specificity and potential distances over which they can operate.  An operationally effective trap to monitor the Asian longhorned beetle has been a goal of the ALB eradication program since the first beetle was found in New York in 1996. Research on reproductive behaviors has shown that more than one pheromone is involved in the process.  The Semio-chemicals involved have been identified but the location of receptors is still unknown.  Compounds have been selected, evaluated and shown to be effective as lures in adult traps.  Further work to improve the trap design is still needed.

Our Research

Antennal receptors
Work to delineate sensory structures on the antennae of male and female ALB, that might be responsive to chemical attractants has been conducted. Antennae have been examined using light microscopy and scanning and transmission electron microscopy, and a number of types of receptors have been identified.

Pheromones and the development of traps 

The goals of this project are to: 1) characterize ALB behavioral responses to two different pheromones, one male produced and one female produced, as potential candidates for monitoring and/or management of this destructive tree pest, 2) to develop an efficient lure and monitoring trap to monitor ALB at low populations. 

Expected Outcomes

An adult trap that can be used to detect ALB at low population levels. 

Research Results

Antennal receptors

The antenna of each sex has 11 segments – a scape, pedicel, and 9 similar annuli that make up the flexible flagellum. Because the scape and pedicel bear few surface structures, it is unlikely that they are involved in chemoreception. The flagellum is covered with dense hairs arranged in broad alternating black and white bands. The hairs are socketed and their surface is uniformly sculptured with fine ridges running along the axis. The hairs measure approximately 8 μm x 55 μm and appear identical to hairs found on the elytra. Three other types of setae are found on the flagellum. Long hairs (10 μm x 250 μm) are located at the junctions of annuli. There are 12-25 of these per segment; their position indicates that they likely function as mechanoreceptors. Somewhat shorter setae (8 μm x 120 μm) are located just proximal to the junction of annuli (20-40 per segment), and several (2-40 per segment) long setae (8 μm x 350 μm) are located in the midregion of each annulus. Their histology indicates that the setae function as mechanoreceptors. To date, there is no evidence of pores or pore canals within the setae that would be indicative of chemoreception.

Several structures have been identified on the flagellum of male and female ALB antennae that may function as chemoreceptors. The terminal annulus of both male and female antennae has at its apex 11-20 basiconic pegs, approximately 2.8 μm in diameter and height. Pores generally are located near the pegs. However, histological examination of the pegs reveals they closely resemble contact chemoreceptors described in other insects. Observations of adult ALB behavior lend support to the hypothesis that these pegs function as contact chemosensilla.

Shields KS, Mikus DR. 2000. A preliminary description of Anoplophora glabripennis antennal sensory receptors. In: Fosbroke SLC, Gottschalk KW, eds. Proceedings, US Department of Agriculture Interagency Research Forum on Gypsy Moth and Other Invasive Species 2000. Gen. Tech. Rep. NE-273. Abstract, p.55

Laboratory and field evaluation in China of potential lure and trap designs 

In 2002, two male-produced volatiles were isolated from ALB that stimulated antennae of both sexes of ALB. The components were synthesized and consisted of an aldehyde (4-(n-heptyloxy)butanal) and an alcohol (4-(n-heptyloxy) butan-1-ol).
Behavioral tests conducted in the laboratory in 2006 showed a significant attraction of virgin female ALB toward the alcohol. In July 2007 and 2008, field trapping experiments using ALB male-produced pheromone were performed in Ningxia province in China. Results showed a significantly higher total trap catch in the pheromone blend-baited traps, followed by traps baited with the pheromone blend + plant volatiles. Alcohol-baited traps caught only females, supporting previous lab results. Coupling plant volatiles with the male pheromone appeared to increase the attractiveness of females to the traps. 

Over the 2012 and 2013 field seasons, a total of 160 flight intercept panel traps were deployed in Harbin, China, which trapped a total of 65 beetles.  In 2012, traps using lures with a 1:1 ratio of the male-produced pheromone components (4-(n-heptyloxy)butanal and 4-(n-heptyloxy)butan-1-ol) designed to release at a rate of 1 or 4 mg/day/component in conjunction with the plant volatiles (-)-linalool, trans-caryophyllene and (Z)-3-hexen-1-ol caught significantly more A. glabripennis females than other pheromone release rates, other pheromone ratios, plant volatiles only, and no lure controls. Males were caught primarily in traps baited with plant volatiles only. In 2013, 10x higher release rates of these plant volatiles were tested, and linalool oxide was evaluated as a 4th plant volatile in combination with a 1:1 ratio of the male-produced pheromone components emitted at a rate of 2 mg/day/component. Significantly more females were trapped using the pheromone with the 10-fold higher 3 or 4 plant volatile release rates compared to the plant volatiles only, low 4 plant volatile + pheromone, and control.  Our findings show that the male-produced pheromone in combination with plant volatiles can be used to detect A. glabripennis. Results also indicate that emitters should be monitored during the field season since release rates fluctuate with environmental conditions and can be strongly influenced by formulation additives.

Meng, P.S.; Trotter, R.T.; Keena, M.A.; Baker, T.C.; Yan, S.; Schwartzberg, E.G.; Hoover, K. 2014. Effects of pheromone and plant volatile release rates and ratios on trapping Anoplophora glabripennis (Coleoptera: Cerambycidae) in China.Environmental Entomology. 43(5): 1379-1388.

Nehme, M.E.; Keena, M.A.; Zhang, A.; Baker, T.C.; Xu, Z.; Hoover, K. 2010. Evaluating the use of male-produced pheromone components and plant volatiles in two trap designs to monitor Anoplophora glabripennis. Environmental Entomology. 39(1): 169-176. 

Nehme, M.E.; Keena, M.A.; Zhang, A.; Baker, T.C.; Hoover, K. 2009. Attraction of Anoplophora glabripennis to male-produced phermonone and plant volatiles. Environmental Entomology. 38(6): 1745-1755. 

Successful Trapping of ALB in the United States

Over four years of trap evaluation (2009-2012), 1013 intercept™ panel traps were deployed, 876 of which were baited with 3 different families of lures. The families included lures exhibiting different rates of release of the male A. glabripennis pheromone, lures with various combinations of plant volatiles, and lures with both the pheromone and plant volatiles combined. Overall, 45 individual beetles were captured in 40 different traps. Beetles were found only in traps with lures. In several cases, trap catches led to the more rapid discovery and management of previously unknown areas of infestation in the Worcester county regulated area. Analysis of the spatial distribution of traps and the known distribution of infested trees within the regulated area provides an estimate of the relationship between trap catch and the nearest known infestation source.  Studies continue to optimize lure composition and trap placement.

The current findings show that traps baited with male beetle pheromones, presented alone or in combination with plant-derived volatile compounds, can be effectively deployed in invaded landscapes to detect beetles. Indeed, the trapping efforts led in some cases to the detection of previously undiscovered beetle infestations in areas that had not yet been surveyed (for example, in Shrewsbury, MA, east of the core of the infestation in Worcester in 2011). Increasing the speed of detection, thus reducing the time available for beetle population growth prior to the initiation of control efforts, has major implications for management. And the use of trapping data to prioritize areas for tree climbing surveys and other interventions appears to have significant potential in this regard.
Traps may also prove useful as a tool for confirming the presence of infested trees in previously surveyed areas.  In several cases over the course of the four-year study, trap captures guided the eradication team to trees with cryptic infestations that had not been detected in earlier surveys. For example, in 2009, two beetles were trapped in Dodge Park, an area where ALB initial surveys had been completed, and on Doyle Street where host trees are scarce and scattered. Guided by these trap catches, two new infested trees were found in Dodge Park. Similarly, in 2010 and 2011, a total of 4 females were trapped in baited traps hung on the same tree on Lansing Avenue near Indian Lake and finally after surveying the area both years after the beetles were trapped, a small boxelder across the street was discovered that is thought to be the source of the beetles. Furthermore, the identification of some of these infested trees triggered expansion of the regulated boundary to the west. (It is worth noting, however, that in some cases, the source of beetles found in our traps has not been determined despite targeted surveys in the surrounding areas).  

This study complemented and provided a check on the applicability of the findings of both previous and current work in China where higher beetle densities facilitate investigation of lure composition.  Earlier studies conducted in high beetle density areas in China indicated a combination of male-produced pheromone and plant volatiles were most effective at drawing ALB into traps (e.g., Nehme et al. 2010).  These findings are consistent with the overall pattern observed in the current study, though the relatively small number of beetles caught prevents the statistical verification of this pattern.  While the current findings show that baited traps can be effective in trapping beetles in an invaded landscape, more work remains to be done to optimize the lures used. 

An important goal in optimizing the use of ALB traps is to determine the best spacing for the traps.  In the urban/forested landscapes where ALB infestations have been found placing traps in a simple gridded array will not work because trees are unevenly distributed and traps work best when placed on open grown or edge trees.  The current findings provide a preliminary estimate to use for trap spacing of 85 + 21 m based on the average distance a beetle traveled in one season from the closet known infested tree to the trap (see figure).  It should be noted that these distance estimates can only provide a distance to the possible tree the beetle emerged from and not how close to the trap the beetle had to be before it would orient toward the lure.  Also, the current data support only limited conclusions in this regard, because of the relatively small number of beetle captures, potential effects of wind direction and strength, human aided movement (e. g. moving infested work or beetles riding on vehicles) and because not all infested trees on the landscape are known. 

The traps are hung in the lower canopy of trees from June until September. The solution in the cup at the bottom is a saturated salt solution with a couple drops of dish washing liquid added, which will safely kill the beetles that fall into it.  The traps are hung out of reach and checked once every two weeks.  We again this year have traps deployed in Worcester, MA and some of the adjacent towns to assist the eradication program and to continue refining the lures.

Nehme ME, Trotter RT, Keena MA, McFarland C, Coop J,  Hull-Sanders H, Meng P, C.M. De Moraes, M.C. Mescher, and Hoover K. 2014. Development and evaluation of a trapping system for Anoplophora glabripennis in the United States.  Environ. Entomol. 43:1034-1044.

Identification of a sex specific trail pheromone

We discovered a pheromone produced by female ALB that is laid down as a trail when they walk across the surface of the tree. Four chemicals were isolated and identified from the trails of virgin and mated females when they are about 20 days old, which corresponds to the timing of when they are fertile. These compounds are attractive to males, but repel virgin females, probably to help females avoid competition for a mate. This provides us with more information about the series of complex behaviors, as well as chemical and visual cues and signals that facilitate mate location and help the male find the female initially on a huge tree and to relocate her in order to guard her from other males. These compounds have been synthesized and could potentially be useful in managing the invasive beetles in the field using a lure and kill method. 

Hoover, Kelli; Keena, Melody; Nehme, Maya; Wang, Shifa; Meng, Peter; Zhang, Aijun. 2014. Sex-specific trail pheromone mediates complex mate finding behavior in Anoplophora glabripennis. Journal of Chemical Ecology. 40(2): 169-180. 

 

Research Participants

Principal Investigators

• Maya Nehme, Department of Environmental Engineering, Faculty of Agricultural and Veterinary Sciences, Lebanese University, Dekwaneh, Beirut
• Kelli Hoover, Pennsylvania State University, Professor 
• Peter Meng, Pennsylvania State University, recent Master’s Student
• Kelli Hoover, Pennsylvania State University, Professor 
• Aijun Zhang, USDA Agricultural Research Service, Invasive Insect Biocontrol and Behavior Laboratory Research Chemist
• Melody Keena, US Forest Service- Northern Research Station Research Entomologist
• Talbot Trotter, III, US Forest Service- Northern Research Station Research Ecologist
• Kathleen Shields, US Forest Service- Northern Research Station Research Entomologist (Retired) 

Research Funding and Support Sources

• Alphawood Foundation of Chicago (Funding 2006-present)
• USDA Animal Plant Health Inspection Service Plan Protection and Quarantine, Center for Plant Health Science and Technology, Buzzards Bay, MA (supplies 2009 and staff 2010-11) 
• US Forest Service, State and Private Forestry Northeastern Area, Technology & Methods Development    10-CA-11420004-316 (Funding 2011-13) 
• Horticultural Research Institute (funding 2012)
• Massachusetts Department of Conservation and Recreation and Agriculture and Markets (gaining permissions)
• New York Agriculture and Markets (staff 2010)
• ALB eradication programs in New York City and Worcester (climbers and information)

For further details log on website :
https://www.nrs.fs.fed.us/disturbance/invasive_species/alb/risk_detection_spread/adult_trapping_system/