In Ontario, Hemlock Woolly Adelgid (HWA) has been detected for the past three years in the Niagara Gorge. Continued invasion of the Niagara Peninsula by HWA in coming years is very likely, as the map above shows. This map of HWA infestation was created using 2012 data from USDA, and 2015 information from PA, MI, NY. Ontario data is from Canadian Forest Service, and CFIA personal communications.
The map is by county; highlighted counties may be only partially infested. Particularly near the front of HWA expansion this will exaggerate the abundance of HWA – on the other hand, infestations can sometimes go undetected for years which has the opposite result.