Tent Caterpillar Infestation

This observation takes place in May/June 1998 in Woodford, Ontario. I have a memory of a tent caterpillar infestation that overtook and consumed our 25 acres of forest. At one point our entire red brick house was covered in the black caterpillars trying to reach the adjacent forest. The silk web-like nests began to appear on our trees in May and within weeks, the forests foliage was decimated. It looked as if it was mid November with not a single leaf left on the trees. Although this seemed out of the ordinary to me, tent caterpillars are a native species and “outbreaks of forest tent caterpillar occur in Ontario approximately every 10 to12 years and last anywhere from three to six years in a given location” (Ministry of Natural Resources, 2012). Yet, the cyclical spikes of the tent caterpillar outbreak’s do not seem to continue to the same level of severity after 2001 which is shown in Figure 1. My family lived on this property from 1979 to 2000 and recall this outbreak being the most memorable and destructive to the forest. In order to protect the trees mostly made up of sugar maple, oak and beech they had to hire a plane to deploy an aerial spray of pesticides to deal with the caterpillar infestation. I was only a child when this observation occurred but to this day my parents speculate that the caterpillar infestation had to do with the unseasonably warm Winter/Spring temperatures prior to the outbreak in Summer 1998. One example of a weather event that may cause a local caterpillar larvae population to collapse is “a heavy frost shortly after the larvae emerge in the spring as well as cooler spring temperatures or late spring frosts can also delay leaf development or damage host tree leaves, causing the larvae to starve” (Ministry of Natural Resources, 2012, p.6). With the global mean surface temperatures rising it might be inferred that this would produce optimal conditions for caterpillar larvae to survive.

Anthropogenic changes in the forest landscape could be considered as other casual factors. My family informed me that prior to this outbreak they consulted the ministry of natural resources to perform a selective logging of the forest for extra income around 1990-1992. My interpretation is that in addition to climate change, selective logging of the forest could have also weakened the forest ecosystem resiliency to respond to a forest tent caterpillar infestation but it does not explain the general decline in infestations across Ontario after 2001 which Figure 1 displays.

References

Forest Health Update 2020 - Ontario Ministry of Natural Resources and Forestry - 2021 Pest Review Presentation

Ministry of Natural Resources (2012). State of resources reporting: Forest tent caterpillars in Ontario. http://docs.files.ontario.ca/documents/3175/state-of-resources-reports-forest-tent-caterpillar.pdf