MORE TENT CATERPILLARS IN SASKATOON THIS YEAR

It is an annual issue for the city’s urban forest.  Tent caterpillars, cankerworms, and leafrollers are feeding on trees in some areas in the city.  The trees may experience heavy defoliation in some cases, but unless there are underlying issues, the trees will recover and produce new foliage.

 Forest tent caterpillars attack a wide variety of deciduous trees, especially green ash.  The numbers of forest tent caterpillars are high this year especially in areas of the city where green ash is the most common street tree.  Caterpillars can be sprayed with a high pressure hose and washed off of the tree.  Over the next few weeks, these insects will seek shelter and transform into moths.

 Cankerworms, also known as loopers and inchworms, are found primarily on the leaves of American elm and Manitoba maple trees.  The fall and the spring cankerworm species often feed together during June and July.  They can be found hanging from silken threads underneath infested trees and can be a nuisance.

 Leafrollers feed while concealed within leaves that are rolled or tied together with silk webbing.  Ash trees are their preference, but they also attack other tree species.  The larvae will feed in mid- to late-June, but the leaves will remain rolled throughout the summer.

 Tree banding can be used to control cankerworms; however, it is not effective against leafrollers and tent caterpillars.  The best time to place bands on the trees is from September to May to help prevent the wingless adult female cankerworm moths from climbing host trees to lay their eggs.  It is important to remove the bands at the beginning of June because the band can collect moisture and cause the trunk to rot.  Unlike the adult female cankerworm, the female leafrollers and tent caterpillars have wings and will fly from tree to tree to lay their eggs.

 The City of Saskatoon does not control cankerworms, tent caterpillars or leafrollers as they typically do not impact the health of the trees they attack.  Homeowners interested in controlling them on their own trees should consult their local garden centre for advice.  For information on urban pests such as mosquitoes, Dutch Elm disease, wildlife, and tree defoliators, visit www.saskatoon.ca/pests

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