The M.D. of Bonnyville is currently experiencing a third-year Forest Tent Caterpillar infestation. This caterpillar is actually a native species to North America and has been found on many of our area’s poplar and aspen trees, in both urban and rural areas. Caterpillars rarely remain in outbreak numbers for more than two to three years and although not really known, outbreaks occur only every 10-15 years in their cycle.
Caterpillars will last for 5-6 weeks in early spring going into June, they will then pupate in a protected area such as a fence board or post. They will emerge in July as a moth for a short period of 5 days or so in which they will lay their eggs which will then lay dormant for the next 10 months until spring.
When trees lose their leaves, it is termed as defoliation. Defoliation due to Tent Caterpillars may be inconvenient for aesthetic reasons, but tree mortality is very rare. Defoliated trees typically refoliate after caterpillar attacks and experience no lasting damage.
Assistant Ag Fieldman, Janice Boden urges residents to use non-chemical methods to help get rid of these pests as insecticide not only kills caterpillars but will kill the beneficial insects with it. One recommended method is to clip and destroy the tent and caterpillars. The best time to catch the caterpillars in their tents is in the early morning, late evening or on cool, rainy days. We also recommend wrapping a wide band of a sticky substance (Tanglefoot) around the affected tree at chest height. This will work much the same as flypaper. There are also organic insecticides containing Bacillus thuringiensis, which work when larvae feast on leaves that have been treated.
For more information on tent caterpillars, see the Government of Canada webpage below.