October 15, 2015
Research looks to fight EAB
Scientists are scrambling to find ways to stop the emerald ash borer from destroying more North American trees.
In East Asia, ash trees have evolved defences against local insects like the emerald ash borer. To study their adaptations, scientists have grown East Asian species, such as the Manchurian ash, in greenhouses and experimental fields. They allow emerald ash borers to attack the trees, and then observe how the trees fight back.
Researchers at Ohio State University have learned that when an emerald ash borer searches for a tree in which to lay her eggs, she avoids healthy Manchurian ash trees, much preferring a North American ash or a Manchurian ash weakened by drought. As it turns out, a healthy Manchurian ash is a hostile place for beetle progeny. When an emerald ash borer’s eggs hatch in the trees, the larvae struggle to survive.
This may be why the beetle never caused much alarm: In East Asia, it left healthy ashes alone. “It’s going to kill already dying trees,” said Caterina Villari, a researcher at Ohio State and an author of the new study.
Dr. Villari and her colleagues don’t know precisely how drought makes Manchurian ash trees vulnerable to the insects. Drought-stricken trees appear to produce constitutive compounds in the same amounts as healthy trees, but not some of the inducible compounds.
To understand that failure, researchers have been comparing the defences of Manchurian ashes with those of North American species like white ash and blue ash. The researchers have identified an assortment of chemicals that Manchurian ash trees make in higher amounts.
North American ashes may be dying not because they lack a magic antidote against emerald ash borers, but because they may not be producing defensive chemicals in the right balance — or perhaps they just aren’t making them fast enough.
In one particularly intriguing experiment, Justin G.A. Whitehill of the University of British Columbia and his colleagues were able to get North American ashes to fight off the beetles. To do so, the researchers sprayed the trees with a plant hormone called methyl jasmonate. That hormone is released by plant cells that are damaged by chewing insects. It acts as an alarm, prompting the entire plant to make inducible compounds.
Dr. Whitehill and his colleagues reported last year that when they primed North American ash trees with the hormone, the plants killed off many emerald ash borers. The effect was about as strong as a lethal dose of insecticide.
Now researchers are hoping that one day they may be able to identify ash trees making high levels of key chemicals and to develop them into resistant stocks. Scientists may be able to pick out trees that respond with unusual speed to an emerald ash borer attack.
In East Asia, ash trees have evolved defences against local insects like the emerald ash borer. To study their adaptations, scientists have grown East Asian species, such as the Manchurian ash, in greenhouses and experimental fields. They allow emerald ash borers to attack the trees, and then observe how the trees fight back.
Researchers at Ohio State University have learned that when an emerald ash borer searches for a tree in which to lay her eggs, she avoids healthy Manchurian ash trees, much preferring a North American ash or a Manchurian ash weakened by drought. As it turns out, a healthy Manchurian ash is a hostile place for beetle progeny. When an emerald ash borer’s eggs hatch in the trees, the larvae struggle to survive.
This may be why the beetle never caused much alarm: In East Asia, it left healthy ashes alone. “It’s going to kill already dying trees,” said Caterina Villari, a researcher at Ohio State and an author of the new study.
Dr. Villari and her colleagues don’t know precisely how drought makes Manchurian ash trees vulnerable to the insects. Drought-stricken trees appear to produce constitutive compounds in the same amounts as healthy trees, but not some of the inducible compounds.
To understand that failure, researchers have been comparing the defences of Manchurian ashes with those of North American species like white ash and blue ash. The researchers have identified an assortment of chemicals that Manchurian ash trees make in higher amounts.
North American ashes may be dying not because they lack a magic antidote against emerald ash borers, but because they may not be producing defensive chemicals in the right balance — or perhaps they just aren’t making them fast enough.
In one particularly intriguing experiment, Justin G.A. Whitehill of the University of British Columbia and his colleagues were able to get North American ashes to fight off the beetles. To do so, the researchers sprayed the trees with a plant hormone called methyl jasmonate. That hormone is released by plant cells that are damaged by chewing insects. It acts as an alarm, prompting the entire plant to make inducible compounds.
Dr. Whitehill and his colleagues reported last year that when they primed North American ash trees with the hormone, the plants killed off many emerald ash borers. The effect was about as strong as a lethal dose of insecticide.
Now researchers are hoping that one day they may be able to identify ash trees making high levels of key chemicals and to develop them into resistant stocks. Scientists may be able to pick out trees that respond with unusual speed to an emerald ash borer attack.