Forest health monitoring

Collecting information on the health of our forests is important because it helps to:

  • plan forest and pest management activities
  • design research projects, invasive species strategies, and climate change programs
  • evaluate forest sustainability and biodiversity

Forest health monitoring includes:

  • mapping areas to document how much area is affected and how severe the damage is
  • collecting insect and disease samples to track where they occur, how abundant they are, and any changes to tree species affected
  • surveying for specific forest pests, particularly invasive species or pests that affect biodiversity
  • conducting or supporting science projects related to forest health
  • collecting information from long term plots used to assess forest ecosystem health

Each report includes:

  • a summary of forest health conditions
  • amount of area disturbed
  • photos and maps
  • descriptions of damage caused by individual pests, diseases, and weather events across the province

Sometimes, we also include information about future trends/outlook on major pests such as spruce budworm or forest tent caterpillar.

Forest health conditions annual report summaries

2023 forest health conditions

Temperatures were near or slightly above the 30-year average in 2023.

Above average snowfall and rain early in the year was offset with drier conditions for the remainder of the year. Notable weather events included:

  • tornadoes in the south
  • several localized incidences of heavy rain in summer and fall

Area of blowdown recorded was much less than in 2022 at just over 4,000 hectares.

Major pests and areas where tree leaves or needles were eaten:

We continued to document the presence of beech bark disease, which is a combination of an invasive insect (beech scale) and an invasive stem fungus. It continues to spread across Southern Region.

Beech leaf disease was reported in new areas within districts where beech leaf disease was previously reported.

The invasive emerald ash borer beetle was detected in new areas in:

  • the regulated area in Kemptville Kingston and Minden Parry Sound districts in Southern Region
  • Sudbury and Sault Ste. Marie Blind River districts in Northeast Region

Hemlock woolly adelgid was confirmed in three new locations in Southern Region.

The first detections of oak wilt, an invasive disease caused by a fungus, were confirmed in Canada in the Niagara Falls and Springwater areas.

2022 forest health conditions

2022 began colder than the 30-year average, but the remainder of the year was close to seasonal temperatures.

Spring was wetter than usual in the northwest with variable temperatures and precipitation across the province leading into the fall. Notable weather events include:

  • tornadoes in the south
  • several incidences of heavy rain in summer and fall

We aerially mapped more than 10,000 hectares of blowdown, mostly in Southern Region. This area was the most recorded since 2016.

Major pests and areas where tree leaves or needles were eaten:

  • jack pine budworm continued to decrease, but the affected area shifted eastward
  • spruce budworm continued, with the affected area increasing mainly in northeast
  • forest tent caterpillar increased mainly in the northeast, but was also mapped in the northwest
  • spongy moth declined in Southern and Central Ontario, with increased observations of parasites and pathogens
  • large aspen tortrix decreased and was found only in the northeast

We continued to document the presence of beech bark disease, which is a combination of an invasive insect (beech scale) and an invasive stem fungus. It continues to spread across Southern Region.

Beech leaf disease was reported in new areas in districts where beech leaf disease was previously reported.

Unreported occurrences of the invasive emerald ash borer beetle were detected in the regulated area in Bancroft, Sudbury and North Bay districts.

Hemlock woolly adelgid was confirmed in two new locations in Southern Region.

2021 forest health conditions

In 2021, warmer temperatures and a warm, dry spring may have influenced insect pest populations. Notable weather events included tornadoes in the south and increased wildfires, especially in Northwestern Ontario.

Major pests and areas where tree leaves or needles were eaten:

  • jack pine budworm continued in the northwest, but affected a smaller area than in 2020
  • spruce budworm continued in the northeast, with the affected area almost tripling the area affected in 2020
  • forest tent caterpillar was minimal and only mapped in the northeast
  • spongy moth continued to increase in Southern and Central Ontario, affecting a record-high area of the province
  • large aspen tortrix decreased and we found it mainly in the northeast

We continued to monitor beech bark disease, which is a combination of an invasive insect (beech scale) and an invasive stem fungus. We recorded new locations in the Northeast Region.

In 2021, we confirmed beech leaf disease in the Peterborough District and we detected new locations of the disease in the Guelph and Aylmer districts. Researchers confirmed a nematode (worm-like pest) is causing the disease and they are investigating how the nematode spreads.

New occurrences of the invasive emerald ash borer beetle were reported in the quarantined area in Pembroke, Kemptville and Parry Sound districts.

This year’s monitoring challenges included wildfire smoke that blanketed much of the north for extended periods, which made aerial observations difficult, especially in the northwest.

Field staff continued to work safely by implementing COVID-19 protocols.

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2020 forest health conditions

In 2020, Ontario did not have many noteworthy weather events that affected forest health. However, the warmer winter and warm dry spring may have influenced insect pest populations, especially in the south.

Major pests and areas where tree leaves or needles were eaten:

We continued to monitor beech bark disease, which is a combination of an invasive insect (beech scale) and an invasive stem fungus. We recorded new locations in Southern Region.

In 2020, we made few detections of beech leaf disease beyond locations confirmed in previous years. To date, we have only found symptoms of beech leaf disease in Aylmer and Guelph districts and at one location in Aurora District. Researchers are working to determine if the sole causal agent is a nematode or if it is part of a disease complex.

New occurrences of the invasive emerald ash borer beetle were reported in Parry Sound District, which is in the quarantined zone.

Asian long-horned beetle was declared eradicated from the Toronto and Vaughan area by the Canadian Food Inspection Agency.

In 2020, only major disturbances and pests were monitored due to field work limitations related to COVID-19.

2019 forest health conditions

In 2019, Ontario had very few noteworthy weather events affecting forest health.

Areas where tree leaves/needles were eaten:

For the third consecutive year, area with leaves eaten by large aspen tortrix decreased.

A cool, damp spring followed by hot temperatures in early and mid summer were perfect conditions for brown spot needle blight. Over 6,000 hectares of damage were recorded—a record high for the province—primarily in the south.

In 2019, beech leaf disease, now thought to be associated with a nematode, was confirmed in Aurora and Guelph districts prompting work to monitor and understand the effects of beech leaf disease in forests already affected by beech bark disease.

Beech bark disease, which is a combination of an invasive insect (beech scale) and an invasive stem fungus, continued to be monitored with new locations recorded in Southern Region.

The invasive emerald ash borer beetle was found in three central Ontario districts. No new finds of Asian long-horned beetle were reported in 2019. Several other insects and diseases affected forests across the province, but damage was localized.

2018 forest health conditions

In 2018, the main weather-related issue affecting forest health was the hot, dry summer. It led to drought conditions in Southern Ontario, fires in central and northern Ontario, and storms that increased the area of trees that were blown down.

Areas where tree leaves/needles were eaten by:

For the third consecutive year, areas with tree leaves/needles eaten by large aspen tortrix were recorded in the northeast, with a slight decrease in areas affected relative to 2017. In the south, cedar leaves were eaten by leaf miners, with the affected area increasing in 2018

Based on a survey done every two years, the northern extent of ash decline and death from emerald ash borer was recorded in 2018. Traps installed in the northwest to detect whether the invasive emerald ash borer beetle was spreading from Thunder Bay did not capture any beetles. Traps put out for mountain pine beetle in the northwest and for walnut twig beetle, which is the vector of thousand cankers disease, in the south also came up empty. Several other insects and diseases affected forests across the province, but the damage was localized.

The occurrence of beech leaf disease, a disease first found in southwestern Ontario in 2017, increased in 2018 near Aylmer. This finding prompted work with partners, including the United States, to discover causes of the disease.

Earlier reports

Please contact us for earlier reports or if you need accessible formats or communications supports.