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Forest Tent Caterpillars

This year Forest Tent Caterpillars or better known to some as Army Worms, have invaded much of Virden and area. Groups of these worms are known to take over, and eat all the leaves off of hardwood trees.
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This year Forest Tent Caterpillars or better known to some as Army Worms, have invaded much of Virden and area.

Groups of these worms are known to take over, and eat all the leaves off of hardwood trees. Forest Tent Caterpillar populations have a natural cycle of about eight years. In this time, the numbers will slowly increase, peak and then crash.

Manitoba Habitat Conservation Specialist, Carol Graham said, “The Forest Tent Caterpillar is likely entering into the peak phase making their numbers more noticeable, which may also be in association with the mild conditions of this past winter. The high population phase can last for two to three years, depending on conditions.”

These caterpillars are natural to this region; defoliating aspen, ash, maple and birch trees. “Healthy trees will produce leaves following initial defoliation, especially when the growing conditions are favorable. Repeated defoliation over two - three years will stress trees and reduce their resilience to the disturbance, making them more susceptible to other environmental stressors such as drought or other insect infestations,” Graham explained.

With Forest Tent Caterpillars being common in this region, it is a good idea to know how to control them. Graham explained, “Insecticides can be applied, typically in areas where the population has reached a level where severe defoliation is a concern or aesthetics. Biological control sprays can be used - Bt - that targets just caterpillars with no harm to other types of insects. With milder infestations, permitting natural processes and predators as a control is recommended.”