Emerald ash borer, Agrilus planipennis (Fairmaire) is a wood boring beetle that is an invasive pest to ash trees (Faxinus spp.) in North America. In 2014, it was reported that emerald ash borer had infested white fringetree (Chionanthus virginicus L.) in Ohio. Since the initial finding of EAB in the U.S., infested white fringe trees have been found in 9 states while EAB is continuing to broaden its geographical range. We reexamined white fringetrees (n=168) in Illinois, Indiana, Ohio, and Pennsylvania that had been previously examined for EAB attack in 2014 and 2015 in the summer of 2018 to determine the fate of the white fringetree: whether the trees were still under attack or if the trees were relieved from attack as the beetle populations declined. We assessed EAB infestation rates, which included presence or absence of EAB larval galleries in the branches, adult emerald ash borer exit holes on the branches, canopy health rating of the tree, and epicormic sprouting on the tree. The current status of the white fringetrees were related to their status in 2014-2015 using Fisher’s test, ANOVA, and binary regression.
Results/Conclusions
We found that attack rates declined, canopy health improved, and there was decreased epicormic sprouting coinciding with decreasing beetle densities in the area. In 2014-2015, 47 white fringetrees were infested out of 178. Only 12 of the fringetrees were re-infested in 2018 and 9 were newly infested. The majority of the trees were never infested (113) while 31 of the previously infested trees were not re-infested (abandoned). Relative to their canopy health rating in 2014-2015, the canopy health rating of the newly infested trees declined by 46% along with the canopy rating of re-infested trees declining by 30%, whereas the canopy rating of the trees that were abandoned improved by 20%. Newly infested trees showed 75% more epicormic sprouting, indicating that they became stressed from attack, while epicormic sprouting decreased by 34% in abandoned trees, indicating that they are becoming healthier in the absence of EAB. Tree diameter played a role in infestation status: trees that were never infested were significantly smaller than trees that had been previously attacked. Our findings suggest that infestation rates will rise while health of white fringetree will fall as beetle populations move through an area.