Category Archives: Insects

The Tale of Two Beetles: How management options differ between beetles

ALB larva located in the xylem (wood). Image courtesy Joe Boggs

By Joe Boggs, Amy Stone, and Dan Herms

EAB is now found in multiple locations in North America, with very large populations in many U.S. states, as well as Ontario. Therefore, the beetle represents a clear and present danger to ash trees throughout a large area of North America. ALB was first found on the continent in 1996; even now, populations remain small and isolated compared to EAB.

The management strategy for ALB is eradication with the overarching goal to eliminate ALB from North America. It has successfully been eradicated from Chicago, Ill., Staten Island, Manhattan, and Islip, New York, two locations in New Jersey, and from Toronto. However, successful eradication depends on continued vigilance and early detection. While ALB was declared eradicated from Toronto, an infestation was recently found in Mississauga, which is located just west of Toronto. This new infestation will be targeted for eradication.

Although EAB cannot be eradicated because it is so widespread, ash trees can be successfully protected against EAB through treatments with systemic insecticides. However, it is important to remember treatment success is measured by the health of the canopies, and not by the number of beetles killed. EAB larvae feed exclusively on the phloem where they are vulnerable to systemic insecticides. Adult EAB beetles are also killed when they feed on the leaves of systemically treated trees. Systemic insecticide treatments are highly effective in EAB suppression; however, the overarching management goal is very different from ALB. Maintaining a full canopy does not require 100 per cent efficacy as every EAB beetle does not need to be killed.

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The Tale of Two Beetles: How they kill trees

By Joe Boggs, Amy Stone, and Dan Herms

Both beetles are tree-killers and exhibit no real preferences for stressed versus healthy trees. However, EAB only infests and kills trees in one genus (Fraxinus), while ALB infests and kills trees in 13 genera. Trees considered good hosts of ALB include:
Acer (all maple species);
Aesculus (horsechestnuts and buckeyes);
Ulmus (elms); and
Salix (willows).

Trees considered ‘other’ hosts include:
Betula (birches);
Platanus (sycamore/plane trees);
Populus (poplars);
Albizia (mimosa);
Cercidiphyllum (katsura);
Fraxinus (ashes);
Koelreuteria (golden rain tree);
Sorbus (mountain ash); and
Celtis (hackberry).

While the good hosts in this list of genera are generally considered the trees most commonly attacked by ALB, all these trees can be attacked and killed by ALB.

Read the full article: The Tale of Two Beetles

The Tale of Two Beetles: What to look for

EAB creates a characteristic ‘D-shaped’ emergence hole. Photos courtesy Joe Boggs

ALB are bigger beetles, measuring around 25 to 40 mm (1 to 1.6 in.) in length.

By Joe Boggs, Amy Stone, and Dan Herms

EAB is a much smaller beetle, measuring around 10 to 13 mm (0.4 to 0.5 in.) in length. Adults have a flat back and round ‘belly’ when viewed head-on, which is the orientation of the beetle as it emerges from trees. Thus, EAB creates a characteristic ‘D-shaped’ emergence hole. Owing to the beetle’s small size, the holes are only around 4 to 5 mm (0.2 in.) across the flat side of the ‘D.’ The relatively small size of the exit holes makes finding them difficult until trees are heavily infested. Adding to the challenge is the tendency for the beetles to first infest the uppermost and outermost branches and then gradually work their way inward and downward with each successive generation. Consequently, exit holes are usually found at eye-level only when infested trees have been almost completely used by the beetles.

ALB is a large beetle, measuring around 25 to 40 mm (1 to 1.6 in.) in length. They have characteristically long antennae, with each one measuring as long as 40 to 50 mm (2 in.). The beetles produce large, round exit holes that can be almost 10 mm (0.4 in.) in diameter. Since the larvae feed deep within the xylem, the exit holes extend deep into the tree. Inserting a pencil into an exit hole is a good way to determine whether the hole was produced by a xylem-emerging borer. This is the so-called ‘pencil test.’ ALB does not appear to follow the same distribution pattern within a tree as EAB and exit holes are almost as likely to be found at eye-level as they are high in the tree’s canopy.

Read the full article: The Tale of Two Beetles

The Tale of Two Beetles: Where they came from

In 2003, Asian longhorned beetle (ALB)—Anoplophora glabripennis—was found in Toronto. Photos courtesy Joe Boggs

By Joe Boggs, Amy Stone, and Dan Herms

Both insects were accidently introduced into North America; however, EAB appears to have had a single point of introduction in a suburb of Detroit, Mich., whereas ALB has been introduced from China to multiple sites in North America. So far, no ALB infestations have been found to be linked to other infestations in North America; all the beetles that began new infestations arrived directly from China. However, there has been a repeating pattern for each new infestation where a single point of introduction from China was then followed by multiple infestations within the region, which was the result of the movement of infested wood or other material before the discovery of ALB in the area.

Although ALB’s 1996 discovery came six years before EAB, the latter has become much more widely distributed in North America (even though ALB was introduced to multiple locations). Explanations for this disparity in the current distribution of the two beetles include differences in signs and symptoms, and thus the ability to detect the beetles, as well as their behaviour.

Read the full article: The Tale of Two Beetles

Emerald ash borer (EAB)—Agrilus planipennis—was discovered in Toronto in 2007.

The Tale of Two Beetles

Photo courtesy Joe Boggs

By Joe Boggs, Amy Stone, and Dan Herms

Asian longhorned beetle (ALB)—Anoplophora glabripennis—was discovered in Toronto in 2003. In 2007, emerald ash borer (EAB)—Agrilus planipennis—was also spotted in the city. This was the first time the two non-native tree-killing beetles were known to exist in the same geographical location in North America. It is now known the two insects actually overlapped in Chicago, Ill.; however, it was not known at the time of the ALB discovery in 1998 that EAB had established beachheads in North America.

In 2011, ALB was found in Bethel, Ohio, a small rural town about 40 km (25 mi) east of Cincinnati. EAB had been discovered in the region in 2008; ash trees were being killed by EAB within a few miles of the ALB infestation. This was the third time in North America the two non-native tree-killers intersected.

The convergence of EAB and ALB in the same geographical location may create considerable confusion because when people hear ‘ALB,’ they may think ‘EAB’ (and vice versa). Of course, the two beetles are very different in all aspects, including:
● biology;
● behaviour;
● spread;
● distribution; and
● management options.

Read the full article: The Tale of Two Beetles