Living with ‘Yule Tradition’ Insects

The Christmas tree is an old tradition that Americans wish to take with them wherever they go. This creates a minor industry for Christmas tree growers who can market their trees at a premium overseas. This creates a major headache for interdiction of invasive insects.

Christmas Tree growers may have problems protecting their crop from invasive insects. Recently Maine has encountered the elongate hemlock scale, an invasive pest. Invasive species may damage the trees and even worse for the growers, lead to a quarantine that restricts shipments of trees or requires expensive insecticide treatments.

The bigger problem is at the other end; Christmas tree growers shipping hitchhikers on their trees that become invasive in their destination. The most vulnerable ecosystems are islands. Islands have many unique species that have evolved in the absence of competition from other species of insects and animals. The ocean is a barrier that restricts new colonists that may establish and lead to extinction of native species.

Christmas trees are large living organisms that provide a multitude of sites for harboring unwanted invasive species. Recently, the island of Guam intercepted a shipment containing black widow spiders.

About 100,000 Christmas trees arrive on the island of Oahu every Christmas. This is an enormous volume and it is not possible to thoroughly inspect every tree at port. Some of the exotic species that have been detected include salamanders, tree frogs and slugs.

Total production capacity of Christmas trees on Hawaii is only 9000. Hawaii must import Christmas trees to satisfy demand. The Christmas tree issue sparks controversy between traditionalists who want trees whatever the cost and those who are low key and elevate concern for the ecosystem above tradition. Interestingly, there is no mention of an Obama Christmas tree in Hawaii. Maybe the Obamas are content with the big one in Washington?

Invasive species are an added cost to the price of a Christmas tree. As the invasives threat increases, the cost of trees will rise due to increases in inspection and treatment costs. The Christmas tree industry has a vested interest will fight to keep their small businesses. However, the forces for new traditions- artificial trees, decorating live trees and use of non-traditional trees as Christmas trees all are gaining momentum.

One way to control export of invasive species and protect export markets is to inspect the trees before they leave port. Oregon alone harvests over 7 million Christmas Trees annually, an overwhelming task for inspectors.

Of special concern are yellowjacket queens that shelter in Christmas trees to overwinter. Hawaiian regulatory officials are concerned that German yellowjacket, Vespula germanica, an invasive species now found throughout most of the United States, including Oregon, will find its way to Hawaii on the Christmas tree express. Our most common native yellowjacket, V. pennsylvanica, invaded the islands years ago and forms enormous colonies there.

Careful inspections are needed to ensure that this:

Yellow Jacket in Christmas Tree

Does not become this:

Giant Yellow Jacket Nest Fills the Interior of an Abandoned VW.
Under warm year round conditions, nests can reach enormous size.

Merry Christmas

About jjneal

Jonathan Neal is an Associate Professor of Entomology at Purdue University and author of the textbook, Living With Insects (2010). This blog is a forum to communicate about the intersection of insects with people and policy. This is a personal blog. The opinions and materials posted here are those of the author and are in no way connected with those of my employer.
This entry was posted in Environment, Invasive Species, News, Pest Management, Policy. Bookmark the permalink.

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