Elm spanworm research on campus
Turning against the worm
By Deborah Inkpen
These bags covering maple trees on the St. John’s campus are part of a research project on the dreaded elm spanworm. (Photo by Chris Hammond)
Master’s student Heidi Fry is doing research on the elm spanworm outbreak in St. John’s. “My research is focused on why this outbreak has occurred in St. John’s and how the population will eventually collapse,” said Ms. Fry.
One of her experiments involves assessing the natural mortality of the different life stages of the elm spanworm egg, larvae, pupae and adults. She is also assessing the effect that tree quality will have on decreasing the elm spanworm population. A part of her experiment is being carried out on six sycamore maples on trees near the St. John’s campus residences.
“There are five pairs of sleeve cages on each tree 10 cages in total on each tree,” she said. “For each pair of cages there is a control cage and a treatment cage.
“The control cage does not contain elm spanworm larvae, so there will be no defoliation within this cage. The treatment cage contains elm spanworm larvae so the part of the branch in this cage will be completely defoliated.”
Next year larvae will be put in both treatment and control cages to determine if the leaf quality has decreased because of the previous year’s feeding, she said. “This will be determined by assessing elm spanworm survival, sex ratio and reproductive capabilities. If host quality is decreasing because of repeated defoliation than elm spanworm survival rate and reproductive capabilities may decrease and therefore the population size will start to decrease.”
Ms. Fry graduated from Memorial with a B.Sc. (Hons.) in biology this past spring and is currently a candidate at the University of New Brunswick, supervised by Dr. Dan Quiring, and co-supervised by Dr. Krista Ryall, Canadian Forestry Services in Corner Brook.