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The hemlock woolly adelgid (HWA, Aldelges tsugae), an invasive forest pest, was recently confirmed in several locations around the southern and central gullies of Canandaigua Lake. While this might be news to those in Ontario County, iMapInvasives verifies HWA in 12 of the 17 counties that make up the Finger Lakes region. This is bad news for watershed managers and homeowners around these steep ravines where hemlocks serve as a key tree species that holds soil in place and shades stream corridors.


Hemlock Woolly Adelgid Distribution Map. Photo credit: NYS DEC

Hemlock woolly adelgid is a small, aphid-like invasive insect that is native to Asia. It attacks hemlock trees by feeding deep within the plant tissue through the underside of the base of the hemlock tree needles. HWA taps into the tree’s food storage cells directly, leading to a disruption of the flow of nutrients and eventual mortality of the tree. HWA are best identified in the winter when they cover themselves in a white, waxy coating that is easily detectable as small white balls at the base of the needles of a hemlock branch.


Hemlock woolly adelgid on the underside of a hemlock branch. Photo credit: Mark Whitmore

HWA poses a serious threat to watershed health as hemlocks act as a keystone species in this community. Hemlocks typically grow in gullies where their roots hold the soil in place on steep slopes. When hemlocks in these locations die, the slopes are more susceptible to soil erosion, which can lead to water quality issues. Soils hold nutrients such as phosphorus and nitrogen, and excessive nutrients in a lake can result in unwanted algal blooms, aquatic ecosystem damage, and poor water quality. Without hemlock to protect the integrity of the ecological community, areas become easily degraded.


Hemlocks along the steep ravine at Bahar Nature Preserve. Photo credit: Hilary Mosher

Fortunately, it is possible to protect hemlocks from HWA through chemical application, although care must be taken to avoid excessive use within the watershed. Chemical pesticides are available for use by homeowners or via licensed chemical applicator to save hemlock. Chemical treatments have proven to be highly effective and last up to seven years. A biological control may soon be a management option as research is currently underway to determine the efficacy of a non-native beetle on HWA containment.

Cornell Cooperative Extension in Onondaga County has been actively educating the community about an HWA infestation discovered on the shores of Skaneateles Lake this past summer. Workshops, public forums, and now winter hikes have been used to engage the community in identifying the organisms, steps to take to report an infestation and ways to treat infested trees. They are also working alongside Mark Whitmore at Cornell University to create insectaries to grow and apply biocontrols to help deter the spread of this invasive.


Jessi Lyons and Roy Widrig (CCE Onondaga County) showing community members how to identify HWA on Bahar Nature Preserve. Photo credit: Hilary Mosher



The temperatures may not be above freezing, but now is the perfect time to get outside and look for this invasive. Hikes are being lead in Onondaga County, the Finger Lakes National Forests, and Ontario County.


Saturday, January 31st, 9 -10:30 am – Monitoring Hike at Green Lakes State Park, Fayetteville, 7900 Green Lakes Road, Fayetteville, NY 13066 (315) 637-6111

Saturday, January 31st, 11 am -12:00 pm – NY iMap Invasives Training, Onondaga Free Library

Monday, February 16th, 9 -10:30 am – Bear Swamp State Forest

Hikes and iMap Training are free but registration is required. Families are encouraged to attend and snowshoes may be available for youth on a first come first serve basis. Please call (315) 424-9485 ext. 231 or email kaf226@cornell.edu to register.


A second public open house and field tour at the Finger Lakes National Forest (FLNF) is scheduled for Saturday, January 31st 2015, details as follows:

  • Location: Hector Ranger District office – 5218 State Rte. 414, Hector NY 14841
  • Schedule: 9:00 a.m. to 10:30 open house.  Field tour departs the Ranger District at 10:30 to tour an HWA infested site on the FLNF, concluding at 12:00. Open to all.

Saturday, Feb 7th, HWA Volunteer Training, 10:00-1:00pm, Letchworth State Park Main Office


Monday, February 16th, 9 -10:30 am – HWA Volunteer Training HIke,  Bear Swamp State Forest.  Please call (315) 424-9485 ext. 231 or email kaf226@cornell.edu to register.


Wednesday, February 25, 6-8 PM.  Invasive species identification and management workshop. Cornell Cooperative Extension of Ontario County, 480 North Main St, Canandaigua. Workshop is free but registration is required. Please contact Emily Staychock, ecs268@cornell.edu  (315) 536-5123 x4127


Thursday, February 26, 6-8 PM. Invasive species identification and management workshop. Cornell Cornell Cooperative Extension of Yates County, Yates County Building, 417 Liberty St., Penn Yan. Workshop is free but registration is required. Please contact Emily Staychock, ecs268@cornell.edu  (315) 536-5123 x4127


For more information about HWA, workshops, hikes, or management options, please contact Hilary Mosher, Finger Lakes Partnership for Regional Invasive Species Management (PRISM): mosher@hws.edu; 315-781-4385 or Emily Staychock, Cornell Cooperative Extension: ecs268@cornell.edu; 315-536-5123 x4127 or please visit www.nyis.info or http://wnyprism.wpengine.com/ for more information about hemlock woolly adelgid or other invasive species.



CCE Onondaga County leads an HWA monitoring hike at Bahar Nature Preserve. Photo credit: Hilary Mosher