A few Bah-Hum-“Bugs” amidst your holiday cheer

The holiday season is full of traditions, many which involve the use of plants that are used for decoration, such as trees and wreaths.

The holiday season, particularly Christmas, is full of traditions passed down from generation to generation. Several of these traditions also involve various plant parts that are used for decoration and other holiday observances. This article explores in a light-hearted way some of the “downsides” that can be associated with those traditions as it relates to the spread of plant pest problems. 

Bah-Hum “Bug” #1

Probably one of the most recognizable symbols of Christmas is the Christmas tree. Michigan is still one of the leading states (i.e. third largest producer) when it comes to the production of Christmas trees. In fact, about three million trees are expected to be harvested in Michigan this holiday season and shipped to many states across the country. But did you know that Michigan-grown Christmas trees that are shipped out of state must first be inspected and certified by the Michigan Dept. of Agriculture and Rural Development (MDARD)?   

Since the 1990’s when the invasive gypsy moth insect spread across Michigan, Michigan Christmas trees have been inspected by MDARD officials to be sure that there are no gypsy moth egg masses attached to the trees that could be inadvertently shipped to other states. During the course of the growing season, Michigan Christmas tree growers must monitor and manage their trees to prevent adult gypsy moth females from laying their eggs on the trunk and branches of Christmas trees. But growers in Michigan have been doing this for so long is almost a “tradition” for them by now! 

Bah-Hum “Bug” #2

While on the topic of Christmas trees, let’s point out the potential threat posed by artificial Christmas trees manufactured in other countries. Several years ago (2004) shipments of artificial Christmas trees produced in China were confiscated and quarantined in Michigan. The trees had plastic “branches” but the trunks were made from wood. Some of the trunks of these artificial trees were found to be infested with the exotic brown fir longhorned beetle (Callidiellum villosulum (Fairmaire). In some cases, adult beetles were even borrowing out of the trunks of the trees. 

As such, these artificial trees posed a potentially serious invasive pest problem if those beetles had escaped into the environment. While this news did not necessarily make major headlines in the state – almost every real-tree Christmas grower probably had a good laugh along with a copy of the news article pinned to their office bulletin boards! 

Bah-Hum “Bug” #3

Ever get caught under the mistletoe at Christmas? (Smooch-smooch). Well, whether or not you have or have not – did you know that mistletoe is a parasitic plant that could also be potentially invasive? Mistletoes grow world-wide but there are only about two species native to the United States – the American Mistletoe (associated with the kissing custom) and the Dwarf Mistletoe.  However, mistletoe is not found growing in all 50 states of our country and therefore could be accidentally exported into these mistletoe-free states on infected plant material, mistletoes grow mostly on trees and shrubs. 

Moreover, mistletoe plants have characteristics that make them very adaptive and easy to spread– making them a potentially invasive species. For example, the seeds of mistletoe are sticky which enables them to easily adhere to any uninfected branch or trunk they come in contact with. In addition, the seeds are forcibly expelled from their berries and can be ejected up to 50 feet from a tree infected with mistletoe. Thus, mistletoe could be viewed as potential invasive – despite a lot of “good” attributes such as providing food, cover and nesting sites for birds and other wildlife. 

We live in a global era, we export goods across the world and import goods from nearly every country into the United States. There is always the possibility that insect and disease pests can be accidentally transported along with these goods – whether it’s on the product itself or the shipping containers used to transport the cargo. Without due care and diligence, we could be importing the next invasive pest problem, along the lines of gypsy moth or emerald ash borer.

As part of the effort to reduce the chance of new forest pests from moving into Michigan, Michigan State University has launched a statewide effort to help residents learn about the risks and impacts of invasive forest pests. Funded by the Michigan Invasive Species Grant Program, the MSU “Eyes on the Forest: Invasive Forest Pest Risk Assessment, Communication and Outreach Project,” links research with outreach and communication projects through the MSU Department of Entomology and Michigan State University Extension.  For more information, go to the Michigan Eyes on the Forest webpage or the Midwest Invasive Species Information Network webpage.