SASKATOON — Cankerworms and leafrollers have again become a recurring problem for Saskatoon's urban forest. While the infestation may result in significant defoliation of trees, it is essential to note that, unless there are underlying issues, the affected trees will recover and produce new foliage.
Cankerworms, also known as loopers and inchworms, primarily target elm, ash and maple tree leaves. Both fall and spring cankerworm species tend to feed together during June and July. These pests can often be spotted hanging from silken threads underneath infested trees and become pretty bothersome.
Conversely, leafrollers feed while concealed within leaves that are rolled or bound together with silk webbing. Although ash trees are their preferred hosts, they also attack other tree species. While the larvae feed during the mid-to-late part of June, the leaves remain rolled throughout the summer.
Tree banding can be employed to mitigate the presence of cankerworms; however, this method is ineffective against leafrollers. The optimal time for placing bands on trees is from September to May, as it helps prevent the wingless adult female cankerworm moths from climbing the host trees to lay their eggs.
Removing the bands at the beginning of June is essential to prevent the accumulation of moisture, which can lead to trunk rot. Unlike adult female cankerworms, female leafrollers possess wings and fly from tree to tree to deposit their eggs.
The responsibility for controlling cankerworms, forest tent caterpillars, and leafrollers falls outside the purview of the City, as these pests generally do not pose a significant threat to the overall health of the affected trees. Homeowners interested in safeguarding their trees from these pests are advised to seek guidance from horticulture professionals.
For further information on Dutch elm disease, wildlife, tree defoliators, and urban pests like mosquitoes, please visit www.saskatoon.ca/pests.
