Beetle Infestation Threatens Monarch Butterfly Sanctuary

Harsh winter conditions can kill the monarchs at the high-altitude Mexican reserve. That means the insects are threatened by the loss of trees, whether they are felled by loggers or killed by the bark beetles.

Environmental officials in Mexico are battling an unprecedented beetle infestation that threatens to destroy the forests of the monarch butterfly’s winter home.

After decades of battling illegal logging in the monarch sanctuary, biologists and park workers have been forced to selectively cut down infected trees in an attempt to stop the beetles from spreading.

Bark beetles have existed for some time in the monarch reserve, usually attacking only a handful of trees at any one time. But drought earlier this year weakened as many as 9,000 oyamel firs, allowing the beetles to burrow in and tap the trees’ nutrients.

Pesticides would be the most effective way to eradicate the beetles, according to biologists, but they would also kill the butterflies if the winged insects arrived soon after the insecticides were applied.

So park officials are fighting the infestation on a tree-by-tree basis. Bark is removed from the felled trees and buried. The remaining wood is being taken away to prevent the beetles from spreading.

The eradication efforts must stop once the butterflies arrive in November.

The forest canopy is critical to sheltering the monarchs from freezing rain and cold high-altitude nights during their five-month winter stay.

Photo: Cathy Keifer