DECEMBER
2012

 

By
Tom Turpin
 
Professor of
Entomology
Purdue University

 

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Check out these books by Tom Turpin:

Flies in the face of fashion

What's Buggin You Now?

 

 

 

12-13-12

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Christmas Vegetation
Good Bug Food


A Christmas season without traditional decorations wouldn't be quite as festive. All kinds of items are used to adorn our homes and businesses at this time of year - strings of lights, candy canes, sleigh bells, nativity scenes and plants.

Yes, plants. Many varieties of trees, including firs, pines, spruces and cedars, are decorated for Christmas. The 2012 national Christmas tree in the White House is a 19-foot Fraser fir. Fraser firs are the most popular species for Christmas trees, according to the National Christmas Tree Association.

poinsettia
Poinsettia whitefly damage
(Photo by James Castner, University of Florida)

The poinsettia is a well-known plant around Christmas time. This plant is native to Mexico and Central America where it can grow up to 16 feet high. Each year, hundreds of thousands of the plants are produced in greenhouses for the Christmas market.

The red-and-green foliage makes poinsettias perfect plants for the season. While we might be inclined to conclude that the red part of the plant is a flower, it is not. The red foliage is actually a bract, a specialized leaf that surrounds a flower. In this case, the flower consists of those somewhat inconspicuous little, yellow, bulbous structures at the tip of the plant.

Another plant that shows up at Christmas is mistletoe. Mistletoe is what is called an aerial parasite. These plants hang on the limbs of trees and do not have roots that grow into the soil. Mistletoe was a sacred plant to the ancient Druids. It has long been associated with love and fertility. The habit of kissing under the mistletoe seems to have originated with primitive marriage rites in ancient Greece.

Holly
Holly leaf miner damage

At Christmas time, how would we "deck the halls" without those boughs of holly? There are hundreds of species of holly plants and the ones used for Christmas decorations have evergreen foliage with bright red berries. The berries are beautiful but are toxic if swallowed. In spite of this, a number of birds consume holly berries during the winter months. That is because cold temperatures make the berries safe to eat.

To insects, the plants that serve as Christmas decorations are just like all other plants in nature - a food source. Herbivory, or plant eating, is the most common food habit in the insect world. The type of food that an insect eats has been classified in several studies. Results show that nearly half of the insect species feed on plants. Christmas plants are no different!

Of course, when an insect feeds on a plant that we humans want, the insect is dubbed a pest. Trees destined for the Christmas market have a number of insect pests. The USDA has a pest control guide with a list of the culprits. Among the insects are bagworms, sawflies, gypsy moths, budworms, aphids, spittlebugs, scales, ants, grubs, grasshoppers, bark beetles, wood borers, pine moths and tortoise scale. It is not only six-legged creatures that devour our Christmas trees. The USDA also lists a few four-legged creatures as pests - deer, porcupines, mice, gophers and rabbits.

How about poinsettias? Are they infested with insects? The answer is yes. Christmas poinsettias are grown under greenhouse conditions so the insect pests are similar to other greenhouse plant pests. These include whiteflies, thrips, fungus gnats and an arachnid - spider mites.

What about mistletoe? Do insects feed on it? They do. Because mistletoe is itself sometimes considered a pest to the trees where it grows, insect interest is limited. A few insects, including a weevil, a moth, and some bugs and scale insects, do feed on the foliage. The plant does depend on insect pollinators for successful seed production.

Holly plants also have insects that use them as food sources. There are scale insects and leaf miners found on holly. Holly is also infested with an arachnid called a red mite. The leaf miners get their name because, as tiny maggots, they feed between the cuticles of the leaf and mine out the green material for food. The feeding doesn't hurt the plant. However, the damaged leaves make the plant less appealing as a Christmas decoration. That is, unless an entomologist noticed the plant and no doubt exclaimed, "Wow, look at the leaf miner damage on that holly!"

 

Writer: Tom Turpin
Editor: Olivia Maddox