Frequently Asked Questions

Eastern spruce budworm (Choristoneura fumiferana) is a naturally occurring forest insect in Newfoundland and Labrador and is a member of the diverse family of tortrix moths (leaf rollers). The caterpillars grow to about 2.5 cm long and have black heads and greenish-brown bodies. Adult budworm moths have a wingspan of about 2 cm and are dull grey or rusty brown and have bands and brown spots on the wings. Budworm are cyclic and their outbreaks are part of the natural processes required for renewal and regeneration in forest ecosystem in Gros Morne. Budworm caterpillars feed on the new growth of needles on the tips of conifer branches during early summer, and during outbreaks this can cause heavy defoliation and mortality of balsam fir and spruce trees. Severely affected trees turn a rust colour during late June due to the presence of dried-out needles held together by strands of silk spun by the caterpillars. These dead needles are soon dispersed by wind and rain, giving trees with a greyish appearance by late summer. As older trees die, they will be replaced by new stands of fast-growing young trees, which contributes to diversity in the landscape and to the overall health of the forest.

Budworm are cyclic and outbreaks typically occur at 30-40 year intervals. The last outbreak in the region happened almost 50 years ago, so this outbreak was expected and was even a few years overdue. Since 2006, a spruce budworm outbreak has been moving eastward through Quebec and there is evidence of migration of spruce budworm moths from Quebec to western Newfoundland on prevailing winds. Monitoring shows that spruce budworm numbers have been increasing along much of the west coast of Newfoundland since 2017, including in Gros Morne National Park, and in 2021 localised defoliation started to be noticeable. Budworm outbreaks typically last 9-10 years and then subside due to factors such as reduced food for the caterpillars, increases in populations of natural enemies of budworm, and weather.

Repeated defoliation by spruce budworm will cause many trees to die after 4-5 years. Once the trees are dead, there are many species of insects and fungi that will occupy and feed on the dead trees. Several species of birds and mammals also use cavities in these snags as roosting, denning, or nesting sites. As the canopy opens, more sunlight reaches the forest floor, stimulating a rapid flush of growth by young trees and early successional plants, re-greening the area in just a few years. Older trees are typically more severely affected than younger trees, and so a larger proportion of trees will often die in older forests. Ultimately, an outbreak can help create diversity in the forest landscape and allow for the growth of new stands of fast-growing young trees.

Yes. Evidence suggests that outbreaks have been synchronized between Newfoundland and eastern Quebec for centuries to millennia. There have been four well-documented outbreaks in Newfoundland over the last century, the most recent of which happened in the 1970s.

The Government of Newfoundland and Labrador asked Gros Morne National Park to participate in their spruce budworm control program from 2021 onwards. Following a review of policy and the best available scientific evidence, as well as expert and public consultations, Parks Canada made a decision not to allow Gros Morne National Park to be included in the provincial budworm control program. This decision was based on a variety of considerations, including the potential impact that prevention of a spruce budworm outbreak within the national park would have on the ecological integrity of its forest ecosystem, the advanced stage of the developing outbreak in the park, which may have limited the potential for success, and the results of the public consultations. There was limited and mixed evidence that inclusion of the national park was necessary for the success of the provincial control program, and experts also raised concerns about the open-ended duration of commitment required by the control program, which involves ongoing suppression of budworm. There was concern that this could lead to accumulation of ecological impacts, erosion of ecosystem resilience, and long-term dependence on spraying to prevent a more severe outbreak in the future.

While trees are killed as a result of these outbreaks, other forest species have adapted to take advantage of them. Some bird species move into areas where outbreaks are occurring to feed on the abundance of budworm caterpillars, while species such as wood boring insects and woodpeckers will move in to take advantage of the supply of dead trees. Salmon and trout may also benefit from the presence of additional insects for food. As the forest canopy opens and lets in more sunlight, different species of plants will have better conditions for growth. Parks Canada’s mandate includes protecting the ecological integrity of national parks, which means protecting all the species native to the ecosystems within a national park, as well as the natural processes and cycles that maintain the health and resilience of these ecosystems.

The steps Parks Canada has taken to manage the moose population will continue to help the forest recover from excessive browsing by moose. Indeed, reducing the moose population was seen as being important so that the forest would be resilient and able to regenerate following disturbances such as insect outbreaks. Now that moose numbers have been reduced, young trees that begin to grow after the budworm outbreak will be free from the severe impacts of browsing, allowing them to grow quickly and renew the forest. If there are areas where the impact of moose remains high, the park may consider adjusting the moose hunt to target effort there and give young trees a chance to grow.

If visitors are in the forest during June and early July they may see budworm on the tips of the branches of fir and spruce or hanging from silk threads. Damage the feeding caterpillars are causing to the new growth at the branch tips will cause them to appear red. Another phenomenon that they may notice is small droppings from the caterpillars — known as frass — falling from the trees, for example on the fly of a tent. For a few weeks in mid-July large numbers of budworm moths can be seen, particularly around the crowns of trees and around lights at night. Visitors may also notice an increase in the numbers and variety of bird species, as well as in the number of young birds that are fledged. Some bird species such as Evening Grosbeaks, Bay-breasted Warblers and Cape May Warblers have moved into areas affected by the spruce budworm outbreak so that they can take advantage of the increased food supply.

If visitors are in an area where the forest has been affected by the spruce budworm outbreak, they will see evidence of trees losing their needles as a result of them being eaten by the caterpillars. After 4-5 years of budworm activity, people will increasingly see dead and dying trees. However, these areas should begin to green up rapidly: though the dead snags will be visible for many years, within a few years a dense growth of vibrant, fast growing young trees and shrubs should begin to push up from below.

Budworm are occurring in lowland forests throughout Gros Morne National Park, so if you want to avoid them you could choose one of our trails that passes through non-forest areas, such as the Tablelands Trail or Coastal Trail, or try the Western Brook Pond Trail, which is wide and so doesn’t have overhanging trees. Budworm pupate and emerge as moths by mid-July, so by early August you won’t see them anymore. Gros Morne National Park posts regular updates on trail conditions at:

https://www.pc.gc.ca/en/pn-np/nl/grosmorne/activ/experiences/randonnee-hiking/etat-sentiers-trail-conditions

You can also speak to staff at the Visitor Reception Centre in Rocky Harbour, the Discovery Centre in Woody Point, or by calling the park information line at (709) 458-2417.

The spruce budworm does not pose any risk to human health.

The progress of the outbreak will be unpredictable so it is difficult to know at this time how much timber will be affected within the designated domestic timber harvest blocks in the national park. To address this, the park is taking steps to monitor the progress of the outbreak and map areas where trees are being affected by defoliation. As in the past, and in accordance with the federal-provincial agreement, harvesters will continue to have access to timber within domestic harvest blocks. Trees that die from defoliation still have high value as firewood for several years and, if necessary, the park may take steps to encourage and support harvesting of these trees within the harvest blocks in order to offset harvesting of live trees.

As outbreaks occur every 30-40 years, they provide an opportunity for park ecologists and outside researchers to learn about boreal forests and how they respond to spruce budworm outbreaks. Scientists are studying how other insects react to the outbreak and assessing effects on things such as natural enemies of spruce budworm and forest carbon balance. In addition, by comparing conditions inside and outside the national park, researchers will be able to gather information that can help them determine the success and consequences of the insect control program being implemented outside the national park.

The wet, coastal balsam fir forest of Gros Morne has an inherently low risk of fire, and no major fires have occurred in the park since it was established in the 1970s. This includes following the large budworm outbreak in the 1970s and outbreaks of other defoliating insects in the 1980s and 1990s. Parks Canada is monitoring the impacts of the budworm outbreak and will be conducting a new fire risk analysis for Gros Morne National Park.

Even though the risk of wildfire is considered low and climate change predictions for the park forecast an increase in precipitation in the future, Parks Canada takes the risk of wildfire seriously. The agency has a national approach to support wildfire response at Parks Canada sites across the country and has fire response teams and other resources available to deploy to a park should a need arise.

Another part of being prepared is maintaining strong partnerships. Parks Canada is a member of the Canadian Interagency Forest Fire Centre and shares personnel and equipment with provincial and territorial fire management agencies, such as the Government of Newfoundland and Labrador, when needed.