U of G researchers seeing fewer spongy moths in Guelph parks

Where have the spongy moths in Guelph gone?

Despite how present spongy moths were last spring and summer, researchers from the University of Guelph are noticing a decline in their presence, and other pests, in the trees at municipal parks in Guelph.

Researchers from UofG’s pest lab checking for invasive pests in Riverside Park in @CityofGuelph. Good news. Not finding #Spongymoth nor most other pests. #couldusesomegoodnews pic.twitter.com/XYmqFb1MJK

— David Beaton (@davebeaton4) May 30, 2022

"The spongy moth (caterpillar) decline is surprising," said Reid Harrop, one of the lead's for the research team from the Centre for Biodiversity Genomics at the University of Guelph.

Harrop, Hillary Hale, and 10 other researchers have been out seven hours a day doing field collections for a project that looks to examine the gut microbes in spongy moth caterpillars, eastern tent caterpillars, web worms and emerald ash borers to develop a DNA metabarcoding protocol to reveal an organism's symbiome, which is the community of other species living in or on an individual. This research would help advance knowledge in species interactions which can then be applied to biodiversity science.

Harrop notes they are just starting to see egg masses for spongy moth caterpillars in the areas they have selected. These areas were chosen through the use of tree inventory reports from the City of Guelph.

Jeremy deWaard, associate director of collections at the Centre for Biodiversity Genomics, said the spongy moth population was likely knocked back from disease and parasites in the Guelph area last summer, and the city has now moved past outbreak levels.

“We saw a ton of caterpillar mortality last year in Guelph, especially from the viral nuclear polyhedrosis virus (NPV) and the fungal pathogen Entomophaga maimaiga,” said deWaard in an email.

"I haven't been to Riverside Park yet this spring, but we're certainly seeing a lack of spongy moth caterpillars at several other municipal parks we've examined, as well as here on the University of Guelph campus. I checked on some bur oak, crabapple, Norway maple, and serviceberry trees on the south end of campus, all were heavily infested last year, but there was little to no apparent damage from spongy moth caterpillars, or even egg masses this spring."

Still in the early stages of the project, Harrop notes the weather earlier this spring could have also impacted spongy moth caterpillars. 

"We're still learning as we go," said Harrop.

The research team will continue to visit areas around the city to collect samples until October.