Spongy Moths (LDD/Gypsy Moths) – How can we manage the invasion?

Invasive species are exotic organisms which enter a locality and then dominate/out-compete native species. Many of these invaders have been established for several decades, with the majority of us unable to even recognize them because we are accustomed to their presence. One of these species is the gypsy moth which was introduced into the United States around 1869 from Europe. Since then it has established populations in Canada and is now considered one of the most destructive invasive species in North America.1

Gypsy moth larvae often cause significant damages to native tree species through excessive defoliation (they eat all the leaves off a tree).  These damages sometimes kill trees and can result in significant economic impacts in agriculture and forestry. Like any organism gypsy moths have favourite foods and tend to target certain species of trees more than others! Their favourite food appears to be oak, with their other favourites being aspens and birches in the northern regions; however they can be found on many other deciduous trees, including maples, and even coniferous species, like pines, in more southern regions.2 Gypsy moth outbreaks occur every 7-10 years and 2021 is predicted to be an outbreak year.2

How are gypsy moths expanding their range?

Unlike male gypsy moths, females are unable to fly, meaning that they are unable to spread their eggs over vast distances .3 The main cause of their expanding range is people unknowingly carrying the eggs (for example by bringing wood out of one forest and into another) to a new location, or by eggs spreading through wind dispersal.3 The Land Between is the northern frontier for expansion of the gypsy moth up into Algonquin park and beyond (Figure1).  In fact, egg mass surveys conducted in Ontario have shown that Aurora, Midhurst, Peterborough, Bancroft and Kemptville are likely to see high rates of defoliation in 2021.2 Thus, it is extremely important to control the gypsy moth populations in these areas.

Due to the large negative effects that gypsy moths have on forests it is important that their populations are monitored and subdued. The appropriate management/eradication practices for Gypsy moths changes depending on their life stage (Table 1, Figure 2).

Remember to never transfer wood between locations, and keep an eye out for any caterpillars trying to hitch a free ride! If you find gypsy moths anywhere please report it on EDDMapS (Early Detection and Distribution Mapping System) and remove them if possible. To learn more about gypsy moths and what cities like Toronto are doing watch this video.

Written by: Fallon Hayes, Education and Communications Specialist

Works Cited

1. Liebhold, Andrew M., Joel A. Halverson, and Gregory A. Elmes. “Gypsy moth invasion in North America: a quantitative analysis.” Journal of biogeography (1992): 513-520.
2. https://www.ontario.ca/page/gypsy-moth
3. Sharov, Alexei A., and Andrew M. Liebhold. “Model of slowing the spread of gypsy moth (Lepidoptera: Lymantriidae) with a barrier zone.” Ecological applications 8.4 (1998): 1170-1179.
4. Nealis, Vince. “Still invasive after all these years: keeping gypsy moth out of British Columbia.” The Forestry Chronicle 85.4 (2009): 593-603.
5. BioForest Technologies Inc. (2006). Assessment of gypsy moth populations and potential impacts within the city of Mississauga and recommendations for management. 1-62
6. https://www.canada.ca/en/health-canada/services/consumer-product-safety/reports-publications/pesticides-pest-management/fact-sheets-other-resources/bacillus-thuringiensis-subspecies-kurstaki.html
7. Liebhold, Andrew M., Joseph S. Elkinton, and William E. Wallner. “Effect of burlap bands on between-tree movement of late-instar gypsy moth, Lymantria dispar (Lepidoptera: Lymantriidae).” Environmental Entomology 15.2 (1986): 373-379.
8. Sun, Baojing, Bryan Edward Cooper Bogdanski, and Brian Van Hezewijk. The Economic Feasibiliity of the Gypsy Moth Eradication Program in British Columbia. Canadian Forest Service, Natural Resources Canada, 2019.