Delving into the eyesight of a destructive pest

As emerald ash borers, a species native to eastern Asia, expand across the United States damaging and killing ash trees, researchers are attempting to understand more about how the beetles see color.

The iridescent beetles rely on their color vision to find mates as well as the ash trees that they feed on.

“So far, there is no way to control them,” said Nathan Lord, a postdoctoral researcher at Brigham Young University in a news release. “Many jewel beetles are pest species, causing millions of dollars of damage to trees and crops yearly. The emerald ash borer is one of them, and they’ve killed most of the ash trees in the east.” So far, the ash borers (Agrilus planipennis) have killed over 50 million ash trees in the United States since they were discovered in 2002 in Michigan. Recently, the beetles were found in the western states of Colorado, Nebraska and Texas.

The researchers used DNA sequencing to look at genes involved in seeing color that are expressed in emerald ash borers’ eyes. ©Mark Philbrick

In a study published in the journal BMC Evolutionary Biology, lead author Lord and his colleagues looked at how the beetles see color. From previous research, the team knew that the species is more attracted to purple traps rather than black and green ones.

Lord and coauthors Seth Bybee and Barry Willardson, both professors at Brigham Young, used gene sequencing to determine how different jewel beetle species express genes in their eyes. They found that while jewel beetles lack receptors for blue, they can still see the light in the blue region of the color spectrum.

“Beetles do not technically have the machinery to see ‘blue’ in the way that most other organisms do,” Lord said. To get around this, separate copies of genes for seeing other colors in the light spectrum likely evolved and became sensitive to blue light, he says.

The researchers hope knowledge about the species’ color perception will give them a way to help slow down the ash borers’ reproduction. By pinpointing the proteins in the beetles’ color vision, what they use as visual signals and how they use these signals, the researchers believe the insects’ light-sensitive proteins could somehow be shut down so that the species can’t find mates or ash trees.