Understanding the Emerald Ash Borer Issues
The emerald ash borer (EAB) is an insect native to Asia. It came to North America in the 1990s and has continued to spread, killing millions of ash trees on its path. The lack of effective control measures and the introduction of the insect to distant areas through the transportation of contaminated firewood have facilitated its spread.
How to Manage the Emerald Ash Borer
The EAB is difficult to manage. At the larval stage, it lives hidden under the bark of ash trees. At the adult stage, it can usually be found in the ash canopy, mating and feeding on foliage during its brief twenty-day lifespan. This life cycle provides the EAB with a relatively quiet existence. Infested trees will show no visible signs of attack until three to four years later.
We have very few tools to fight the EAB. In urban areas, felling infested trees is critical to protecting citizens from the dangers posed by these trees. Since infested trees are detected late, cutting them down does not prevent the spread of adult insects. High-value ash trees are treated with an insecticide, which is injected into the base of the trunk and carried up by sap to hinder the development of larvae, when they are not overly abundant.
Other products that attract the insects have been discovered and are used to detect and trap them. Unfortunately, trapping all EAB is not a realistic strategy. We are not, however, out of options. Nature itself has provided us with a powerful and effective weapon that can help to restore the ecological balance. Biological control strategies involve using natural organisms to regulate the insect population. For example, insect pathogenic fungi transmit deadly diseases that are communicable among insects.
Inspired by nature, Québec researchers decided to introduce pathogenic fungi to the EAB population and have them carried by the ash tree. After all, isn’t the ash tree the best positioned to locate its enemy with the help of a partner? The approach developed by the researchers is known as auto-dissemination. It involves installing bright green insect traps at the top of ash canopies, where they will lure EAB. The devices are not your standard insect-killing traps. Here the EAB is attracted and captured, but is only released after it has been infected with a lethal fungus. What we seek to demonstrate now is how disease can spread throughout the ash tree population. Since the traps are only placed in the treetops, where adult EAB feed on leaves, the damage caused to non-targeted insects will be reduced. In other words, bees and other useful insects will not be affected by the traps.
The fungus used in the traps was discovered in Québec by the same researchers. It is a specific fungal isolate known as Beauveria bassiana, which is naturally present all over the world. An isolate in pest control is similar to a cultivar – or plant variety – in agriculture. This fungal isolate has special insecticidal properties. As a result, it can trigger disease in specific insect species, without causing harm to other species.
Insect pathogenic fungus is also completely harmless to mammals, birds and fish. Many Beauveria bassiana isolates are sold in the United States and Europe as biological pest management tools for use in natural settings. Here in Canada, we are leading the way!