Host Range

Emerald Ash Borer: Research and Technology Development Meeting

From: V. Mastro and R. Reardon (compilers), Emerald Ash Borer Research and Technology Development Meeting, Romulus, Michigan, Oct 5-6, 2004. USDA Forest Service publication FHTET-2004-15.

Does Forest Community Structure Influence Susceptibility and Response to Emerald Ash Borer?

Annemarie Smith1, Daniel A. Herms2, and Robert P. Long3

1 Environmental Science Graduate Program, The Ohio State University, 400 Aronoff Laboratory, 318 W. 12th Street, Columbus, OH 43210
2 Ohio Agricultural Research and Development Center, Department of Entomology, The Ohio State University, 1680 Madison Avenue, Wooster, OH 44691
3 USDA Forest Service, Northeastern Research Station 359 Main Road, Delaware, OH 43015

The ability of invasive species to invade native landscapes may be influenced by community composition. Emerald ash borer (Agrilus planipennis) has already caused considerable mortality of ash in southeast Michigan forests and is now invading forests in northwest Ohio. However, the ecological impact of this mortality is unknown. The objectives of this research are to 1) characterize effects of community composition and structure on forest susceptibility to emerald ash borer invasion, and 2) quantify community response to ash (Fraxinus spp.) decline and death. Invaded stands are being characterized by quantifying density and basal area of ash and other woody species, percent canopy cover, and soil moisture along a gradient from dry upland sites to low wetland sites. Degree of emerald ash borer colonization is being quantified by estimating ash canopy dieback and counting D-shaped emergence holes and woodpecker attacks on the boles of infested trees. Community response to ash decline and death is focused on species replacing ash in the canopy, sapling release, and seedling establishment, as well as exploitation of canopy gaps by invasive plants. Plots are being mapped via GIS to provide opportunities for study of long-term effects of emerald ash borer on successional trajectories. This study will increase understanding of impacts of invasive insects on forested ecosystems, and enhance implementation of emerald ash borer containment and eradication efforts.

Host Range of Emerald Ash Borer

Robert A. Haack and Toby R. Petrice, USDA Forest Service, North Central Research Station, 1407 S. Harrison Road, East Lansing, MI 48823

The emerald ash borer (EAB), Agrilus planipennis Fairmaire, is native to China, Korea, Japan, Mongolia, Russia, and Taiwan. Established populations of EAB were first discovered in Michigan and Ontario in 2002, and since then additional infestations have been found in Indiana, Ohio, Maryland, and Virginia. As of October 2004, EAB has only been found to breed in ash (Fraxinus) trees in North America. Ash is the only host listed for EAB in China. Ash is also listed as a host in Japan, as well as elm (Ulmus), walnut (Juglans) and wingnut (Pterocarya). In Korea, elm is listed as a host of EAB.

In 2003 and 2004, we evaluated foliage of several trees and shrubs as food for EAB adults in a series of no-choice and choice tests that were conducted indoors in Michigan. We tested members of the olive family (Oleaceae: Chionanthus, Forestiera, Forsythia, Fraxinus, Ligustrum, Syringa), elm family (Ulmaceae: Celtis, Ulmus), and walnut family (Juglandaceae: Carya, Juglans).

In 48-hour no-choice tests in 2003, EAB adults fed readily on ash, although blue ash (F. quadrangulata) was the least preferred. There was some feeding on the other members of the olive family, such as forsythia, fringe tree, lilac, privet, and swamp privet. There was almost no feeding on elm, hackberry, hickory, and walnut. In two-choice tests, using green ash as the “standard,” EAB fed readily on the other ash species tested as well as the Oleaceae shrub species. There was significantly less feeding on the Juglandaceae and Ulmaceae species tested when in the presence of green ash.

In 2004, we conducted a series of multiple choice tests. In the first test, we used seven species of ash, including five native and two Asian species. Overall, EAB fed most on green and white ash and least on blue ash. Feeding on the two Asian ash species (F. chinensis subsp. rhychophylla and F. mandshurica) was intermediate. In the second test, we allowed EAB to choose among green ash and four shrub species in the Oleaceae. EAB preferred green ash over any of the four shrubs tested, including forsythia, fringetree, lilac, and privet. Of the four shrubs, forsythia was the least preferred. In the third test, we used green ash and four non-ash tree species. Overall, EAB fed almost exclusively on ash while in the presence of hackberry, slippery elm, shagbark hickory, and black walnut.

Host Range and Preference of the Emerald Ash Borer in North America: Preliminary Results

Andrea C. Agius1, Deborah G. McCullough1,2, and David A. Cappaert2

1Department of Forestry, Michigan State University, 243 Natural Science Building, East Lansing, MI 48824
2Department of Entomology, Michigan State University, 243 Natural Science Building, East Lansing, MI 48824

Previous literature on the emerald ash borer (EAB) indicated that, in its native range, this beetle was recovered from several Asian species including Ulmus sp., Juglans sp., and Pterocarya sp., in addition to Asian ash tree (Fraxinus sp.). If EAB can complete development on alternate hosts, impacts of this nonindigenous pest would in North America would increase dramatically.

Our objectives are to 1) determine if EAB can oviposit and develop on potential alternate host species and 2) evaluate preference among four North American species of ash. In 2003 and 2004, we monitored adult landing rates and evaluated early instar development on logs of ash and potential alternate host species placed out in the field and used in no-choice laboratory bioassays. We studied four ash species common in Michigan: green ash (F. pennsylvanica), white ash (F. americana), black ash (F. nigra), and blue ash (F. quadrangulata). Potential alternate host species that we evaluated included American elm (U. americana), black walnut (J. nigra), hackberry (Celtis occidentalis), Japanese tree lilac (Syringa reticulata), hickory (Carya sp.), and privet (Ligustrum sp.). We also assessed host preference with two-choice leaf-feeding bioassays in the laboratory and at field sites with multiple species of ash growing in close proximity.

In the no-choice laboratory bioassay, female EAB laid eggs on all species. There was larval feeding under the bark on all species except hickory. Larval feeding and development on the ash species appeared normal, while development on the non-ash species was highly impaired when feeding was attempted.

Logs (ca 1 m x 150 cm diam) of green ash, white ash, elm, walnut, hickory, and hackberry were attached to t-posts at four sites in the core zone. Similarly-size sections of black drain pipe served as a control. Half of the logs were wrapped in Tanglefoot® to monitor landing rates. Landing rates were similar for all species, although significantly fewer beetles landed on the “control” pipe than on green ash when data from all sites were combined. Logs were dissected to count galleries. Green ash and white ash had 14 and 36 galleries per m², respectively, while elm, hackberry and hickory had zero. Black walnut had seven galleries per m², but all were impaired.

In a field study in 2003, logs of green ash, walnut, and elm were attached to the main stem of infested green ash trees, 5 to 7 meters above ground. We repeated this study in 2004; white ash and blue ash logs were included and logs were attached to infested white ash trees. Logs were dissected in autumn. In both studies, less than four galleries were found on walnut and none were found on elm. Nearly 200 galleries per m² were found on green ash in 2003 and on white ash in 2004.

Host preference was evaluated in 2003 and 2004 at three sites in the core zone that had both green and white ash street trees growing in close proximity. At all sites, there were more exit holes per m² in the green ash trees than in the white ash trees. The level of canopy dieback was also visually estimated for each tree at these sites. In both 2003 and 2004, the green ash trees showed significantly more canopy dieback than the white ash trees. These results and other observations indicate that EAB prefer green ash over white ash when the two species occur together. Studies that are still in progress include a no-choice oviposition bioassay using live trees (green ash, white ash, black walnut, and Japanese tree lilac), a two-choice leaf-feeding bioassay, and evaluation of host preference at two woodlots containing white and blue ash trees.

Observations of the Within-tree Distribution of Emerald Ash Borer in Southern Ontario

L.L. Timms1, S.M. Smith1, and P. de Groot2

1 Faculty of Forestry, University of Toronto, 33 Willcocks Street, Toronto, ON, M5S 3B3
2 Canadian Forest Service, Great Lakes Forestry Centre, 1219 Queen Street East, Sault Ste. Marie, ON, P6A 2E5

One of the greatest challenges facing the successful management of the emerald ash borer (EAB), Agrilus planipennis, is the ability to accurately detect its presence in a stand of trees. External symptoms of EAB infestation are often difficult to see and usually do not appear until after the beetle has already been present for some time. This research aims to address these problems in detection by identifying any patterns that may occur in the within-tree distribution of the larvae of the EAB. Previous research on a native beetle in the same genus, the bronze birch borer (Agrilus anxius), has indicated that the within-tree distribution of Agrilus spp. may be influenced by a combination of stem height, stem diameter, stem aspect, and bark thickness.

To assess what influence these variables might have on the distribution of EAB larval galleries, 93 ash trees from plantations in Essex County, Ontario, were cut and stripped of their bark entirely. Measurements of height, diameter, cardinal direction, and bark thickness were made on all EAB feeding galleries found in the trees. Preliminary analysis shows a directional preference for the southwest, or sunny, side of the trees at all sites (Rayleigh Test Z=337.809, p<0.000001, Oriana Version 2.02a, © 1994-2004 Kovach Computing Services). Feeding galleries were also found to be clustered within a specific range of bark thicknesses and tree diameters within the total range available within the trees. Further analysis is being carried out to clarify these results. It is our objective to use the conclusions of this research in the development of an improved sampling program for the EAB.

Effects of Colored Objects and Purple Background on Emerald Ash Borer Trapping

Gard W. Otis1, Melanie E. Youngs1, and Gary Umphrey2

1Department of Environmental Biology, University of Guelph, Guelph, Ontario N1G 2W1 Canada
2Department of Mathematics and Statistics, University of Guelph, Guelph, Ontario N1G 2W1 Canada

During 2003, male EAB searching for mates landed on and attempted to copulate with both live and dead EAB of both sexes. This strongly suggests that they use visual cues to locate mates. In addition, a 12-day-old female beetle was observed to perform a display that ended in her spreading her green elytra and exposing her magenta abdomen. At the 2003 EAB Research Symposium, Jason Oliver reported that many species of buprestid beetles are attracted to purple panels. We sought to improve EAB trapping and survey efficacy by incorporating green- and magenta-colored objects (ovals and stripes) onto purple panels.

Onto each black Corraplast panel (1 ft²) we affixed nine purple vinyl panels, each 8.9 cm x 8.9 cm and surrounded by a black border. Treatments were randomly assigned to these vinyl squares: stripes (four stripes 5.5 mm wide by 8.9 cm long in green, magenta, or green and magenta), ovals (six ovals with dimensions 16 mm long x 6 mm wide in green, magenta, or green and magenta), metallic ovals (same dimensions; green or magenta), and control (no objects). The panels were stapled onto the south sides of ash tree trunks or onto nearby posts with the tops of the panels at a height of 5.5 ft (1.68 m), then coated with Pestick sticky adhesive. We placed eight traps (half on trees, half on posts) at each of six sites in western Essex Co., Ontario (n=48 traps). Emerald ash borers had been detected at all six sites in 2003 by inspection crews of the Canadian Food Inspection Agency. Trapping was conducted over eight weeks (11 June to 6 August). Beetles were removed every two to three days (on M/W/F). Statistical analyses are preliminary, not final.

Over the entire study, we collected 1,027 beetles (248 males, 779 females). Numbers of beetles trapped were significantly affected by site (P<0.01) and setting (~7X more beetles on panels on trees compared to panels on posts; P<0.01). Treatment effects were not statistically significant. However, numerically more beetles landed on vinyl squares with stripes than those with ovals (perhaps because of greater amount of edge created by stripes), and more beetles were attracted to a combination of magenta + green objects than to only magenta objects; in comparison, panels with only green objects attracted the fewest beetles. Metallic ovals did not attract more beetles in total but may have attracted proportionately more males (31-37 percent male EAB to metallic ovals compared to 19-25 percent male EAB to non-metallic ovals). (Note: the metallic ovals were not identical in color to the non-metallic ovals).

Although EAB were abundant at some sites, trapping success in Experiment 1 was low (0.38 beetle/1 ft² panel/day). Consequently, we decided to compare trapping success with our Avery Graphics purple vinyl vs. the purple Corraplast used in trapping studies conducted by others in 2004. The three treatments in Experiment 2 consisted of three adjacent bands (15" wide x 8" high; 38.1 cm wide x 20.3 cm high) one above the other (order randomly assigned) on ash trees. The band treatments were purple vinyl, purple Corraplast, or clear polypropylene plastic, coated with Pestick. There were 24 replicates (eight sites with three trees/site). We caught 956 beetles in total (17.7 percent males) from 30 June–3 August (34 days). EAB captures did not differ significantly by treatment (purple vinyl, n=372; purple Corraplast, n=197; clear [control], n=387). Our results suggest that low beetle numbers in Experiment 1 were not due to the color of our vinyl: neither purple trap material was more attractive than clear plastic. Most of the beetles were trapped on the lowest band.

We conclude that the difference between EAB captures on tree traps vs. post traps indicates that beetles orient towards and land on trees preferentially over purple traps. Although magenta and green objects may have marginally enhanced EAB trapping success, our data suggest that purple traps are not effective for surveying for EAB or monitoring EAB populations.

Interspecific Variation in Ash Resistance to Emerald Ash Borer

Daniel Herms1, Eric Rebek2, David Smitley2, Pierluigi Bonello3, and Don Cipollini4

1Department of Entomology, The Ohio State University, Ohio Agricultural Research and Development Center, 1680 Madison Avenue, Wooster, OH 44691
2Department of Entomology, Michigan State University, 243 Natural Science Building, East Lansing, MI 48824
3Department of Plant Pathology, The Ohio State University, Columbus, OH 43210
4Department of Biological Sciences, Wright State University, Dayton, OH 45435

Emerald ash borer (EAB) is an aggressive killer of even healthy ash in North America. However, reports suggest that EAB does not devastate ash in Asia, but rather that isolated outbreaks occur in response to stresses such as drought. Thus, emerald ash borer seems to behave in Asia much as its close native buprestid relatives do in North America, colonizing only stressed trees. This implies that Asian ash trees may be generally resistant, with weakened trees preferentially colonized. Native trees may be more resistant to native pests because of natural defenses that have developed over their long coevolutionary history. This hypothesis is supported by a 20 year study of birch resistance to bronze birch borer conducted in Ohio where birches native to North America were found to be highly resistant to bronze birch borer, while European and Asian species were extremely susceptible. To test the hypothesis in the case of ash resistance to EAB, a replicated common garden planting containing native, European, and Asian ashes was established in Novi, Michigan with the following objectives: 1) compare resistance of major North American, European, and Asian ash species to emerald ash borer, 2) identify mechanisms of resistance/susceptibility of ash species to EAB, and 3) determine the effects of drought and other stress on susceptibility of ash species to EAB, as well as North American ash borers. After one year, Manchurian ash (F. mandshurica), which shares an evolutionary history with EAB, had significantly fewer EAB exit holes and minimal EAB induced-dieback, relative to white (Fraxinus americana) and green ash (F. pennsylvanica) cultivars, as well as Northern Treasure ash (F. x ‘Northern Treasure’), which is a hybrid between native black ash (F. nigra) and Manchurian ash. These very preliminary results are consistent with the hypothesis that Manchurian ash is a source of resistance genes to EAB by virtue of their coevolutionary history. However, it remains to be seen if this pattern will hold over time. Work is underway to determine whether this pattern has a phytochemical basis.