2020 In Review: Ontario’s Forest Health Conditions, Featuring Gypsy Moth

Author: Allison Craig, OUFC

In February 2021, the Ontario Ministry of Natural Resources and Forestry (OMNRF) presented their annual report on Forest Health Conditions in Ontario, and things looked a little different this year. Usually, this presentation is hosted in person, providing a great opportunity for forestry professionals and students from across the province to catch-up, network, and socialize. Due to COVID-19, the meeting was hosted virtually this year, but still provided a lot of great information on the pests affecting Ontario’s forests. 

Dan Rowlinson, OMNRF’s Forest Health Field Coordinator, started the presentation by highlighting an unexpected positive outcome of everyone spending so much time at home last year; people really started to notice the importance of trees and green spaces on the landscape and all of the benefits they provide to us. 

The presentation started by covering a few native pests primarily affecting the northern region of the province – forest tent caterpillar (Malacosoma disstria), spruce budworm (Choristoneura fumiferana), and jack pine budworm (Choristoneura pinus). These pests don’t typically show up in urban areas; their impact is mostly seen in the Boreal forest. 

The most prolific urban pest, and the one that Dan spent the most time discussing, is the gypsy moth (Lymantria dispar dispar). This will come as no surprise to those living in southern Ontario; most people either noticed gypsy moth for the first-time last year or have spent the past few years dealing with it, depending on where you live. In 2020, gypsy moth populations exploded across the southern region of Ontario and approximately 600,000 hectares of defoliation was mapped by OMNRF crews during the summer. Dan explained that the gypsy moth has persisted at outbreak levels for the past four to five years in the southwest, and there are a few natural factors that point to a potential collapse on the horizon. Despite these indications, defoliation forecasts for 2021 show a likelihood for severe defoliation again across most of the southern region. Since the OMNRF does not have legal authority to manage trees on private property, nor do they survey within urban boundaries, many municipalities and conservation authorities conduct their own gypsy moth monitoring and management programs. Dan noted that many municipalities and private landowners have already started to organize aerial spray programs for the spring of 2021 to protect trees and keep them green this summer. 

Dan briefly touched on the successful eradication of Asian longhorned beetle (Anoplophora glabripennis) from Ontario, which was announced by the Canadian Food Inspection Agency in June 2020 after five years of no detections. 

OMNRF crews also investigate a few reports of oak decline along the northern shore of Lake Huron. These reports are thoroughly investigated to ensure that oak wilt (Bretziella fagacearum) is not the cause. These reports turned out to be Armillaria root rot causing decline and mortality, and oak wilt has not been confirmed in Ontario. Dan encouraged everyone to continue to be vigilant and monitor for signs and symptoms of oak wilt.  

With the increased number of eyes on the landscape, the OMNRF received a record number of photographs from citizen scientists last year, many inquiring what pest was attacking the trees in their yard or neighbourhood. Dan recommended that people send in not only pictures of the pest in question, but also the damage that the pest has caused. This additional information will help OMNRF staff make more accurate virtual identifications. 

For maps of the OMNRF’s gypsy moth survey results and the full 2020 Forest Health Conditions report, click here.

Gypsy moth (Lymantria dispar dispar) — Photo credit: Sadia Butt, OUFC