WINNIPEG May 03, 2007 - The Insect Control Branch is forecasting a significant cankerworm population in Winnipeg over the next few weeks which will likely have the potential to cause major defoliation of American Elms, Manitoba Maple and Ash trees in many parts of the City where there are large stands of these trees. Current surveillance data indicates that cankerworm populations will be similar to the large populations that the City experienced in the mid to late 1990’s. This forecast is based on:

• Recent data collected from the spring adult female cankerworm moths which were captured on the tree bands.
• Data collected from the fall adult cankerworm female moths which laid their eggs in the fall of 2006.

These populations generally follow a natural five to seven year cycle and have been slowly building up their populations over the past couple of years. Based on previous historical data, the Branch anticipates that this may be the peak of this cycle.

Many citizens of Winnipeg banded their trees this season and this will certainly help to lessen the cankerworm population. Areas of the City which have been extensively banded should experience less defoliation than areas where banding was less prevalent.

The Branch is preparing for a cankerworm control program for boulevard trees and city parks which will probably start in the next seven to ten days and will coincide with emergence of leaves and the presence of larvae (worms) on the leaves. The biological product Bacillus thuringiensis kurstaki (BTk) will be used. The worms can be expected to continue until approximately mid-June. Healthy trees will grow back their leaves by early July.

Homeowners are responsible for control on their property. They can spray their own trees with BTk, which is available at most garden centres or they can contract a tree spraying service by referring to the yellow pages under tree service or exterminators.

Individuals who are opposed to the use of insecticides on or adjacent to their principle residence for the control of cankerworms may register their opposition in writing to the Insect Control Branch, 3 Grey St., Winnipeg, Manitoba, R2L 1V2 or by faxing it to 311 or by registering online at Winnipeg.ca/bugline.

Interested individuals may acquire more information by contacting the City’s Bugline at 311 Monday to Friday from 8:30 a.m. to 4:30 p.m. or by visiting the City’s Insect Control website at Winnipeg.ca/bugline.