EMERALD ASH BORER INTERESTED ONLY
IN ATTACKING ASH TREES

EAST LANSING, Mich. -- It seems that emerald ash borers (EABs) are rather finicky and hard to fool. If they can’t live on an ash tree (Fraxinus spp.)s, they’re not too interested in hanging around. 

There have been concerns that EAB could also infest other types of trees, but research at Michigan State University (MSU) testing EAB preferences for tree species other than ash shows these concerns are probably unfounded. EAB, an exotic wood-boring pest, has killed more than 20 million trees in Michigan, Ohio, Illinois and Indiana to date, most of these in southeastern Michigan. 

“We’ve done no-choice studies in the laboratory with EAB put in clear plastic boxes with various tree species, such as black walnut, Japanese tree lilac, American elm, hickory, hackberry and elm hybrids, which are all related in some way to EAB’s native host species in Asia and could potentially attract EAB,” says Andrea Anulewicz, MSU entomology graduate student working with Deborah McCullough, MSU forest entomologist and primary EAB researcher. “The studies show that EAB are host-specific -- they prefer only ash trees.”
Anulewicz took this study a step further by putting EAB in cages surrounding live trees to see if live trees of various species were more appealing than cut limbs. It didn’t make any difference -- an ash was an ash, and that’s what EAB want.

“They may lay eggs on the other tree species because they have no other choice, but the eggs either don’t hatch or the hatched larvae can’t survive on other tree species,” Anulewicz says.

Not only do EAB prefer ash, but they seem to like certain ash tree species more than others.
“City foresters in southeastern Michigan areas said they noticed that green ash seemed to be preferred by EAB more than white ash,” Anulewicz says. “Our studies also suggest that green ash seems to be the most preferred, followed by white ash. White ash infestations increased in areas where green ash were declining. In two of the areas studied consisting of white and blue ash, only after the white ash were completely infested by EAB did they then switch to blue ash. The blue ash seems to put up more of a fight than other ash species, but EAB shows no mercy. Black ash are also hit hard by EAB.”

Anulewicz notes that the speed in which EAB kills an ash tree seems to depend on the amount of stress the tree is under and the site conditions. EAB will attack a stressed ash tree first, then move to other ash in the area, regardless of stress.

“EAB are fascinating,” she says. “I was amazed at how utterly destructive they are. ‘Pest’ is not a big enough word for them.”

For more information on EAB and EAB research, visit the EAB regional Web site: www.emeraldashborer.info.