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Insects and Christmas trees

One of the joys of the holiday season is the pleasant aromatic smells of freshly cut evergreens. As we enjoy the Christmas trees that we bring into our homes, we can also occasionally bring in some unexpected, and uninvited, visitors.

 While it is possible to find invasive species (see Check Christmas trees and holiday greenery for pests!), most insects we see are just Minnesota natives.
Any insects or insect relatives on
this tree are probably just a nuisance.
Photo:  Jeff Hahn, UMN Extension

Look for aphids among the ornaments!

A common insect people find on Christmas trees is aphids. These soft-bodied, pear-shaped insects laid eggs on trees sometime during late summer and fall. These eggs would normally remain inactive throughout the winter but the warmth of the indoors fools them into thinking spring has arrive so they hatch.

They are very small, about 1/16th inch long. They have piercing-sucking mouthparts and feed on plant sap. Fortunately, they do not injure fresh cut Christmas trees nor will survive on them for long.

Spiders and their babies

Not every arthropod you find is necessarily a tree pest. Another common type of hitchhiker is spiders. Similar to
aphids, they are usually brought indoors as egg sacs and hatch when exposed to prolonged warm temperatures.

However, these spiderlings are unlikely to survive; they will either starve or dry out in a short time.

'Wasp' that??

A resident recently found an ichneumonid wasp, a type of parasitic wasp that was brought in with their Christmas tree. It apparently had a parasitized an insect (like a caterpillar) that had been on the tree during the summer. Although they were concerned it may have been an invasive species, ichneumonid wasps are beneficial and harmless to people.

How worried should I be?

In general, these insects and insect relatives are just nuisances and physical removal is the only necessary control. Don’t use insecticides on any critter you find on your tree; they are not effective in preventing their presence and they are not necessary considering they don’t usually live long.

If there are any insects you are suspicious could be an invasive species, have it identified by an entomologist or landscape professional.

Author: Jeffrey Hahn, Extension Entomologist
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