JUNE
2011

 

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?

 

 

 

06-22-11

Download the audio of On Six Legs: MP3, WMV.

Leaf-Chewing Insects Bug Gardeners


A garden is a plot of ground used for the cultivation of flowers, vegetables, herbs or fruit. There are all kinds of gardens in the world, some specialized for a specific purpose.

A formal garden might have stone paths, fountains, statues and well-manicured plants. Such a garden is for the enjoyment of people who frequent the grounds. There are also flower gardens with plants that produce beautiful blossoms. Herb and vegetable gardens serve the purpose of supplying plant material to be used as human food.

I grew up during a time when almost every family, farm and city alike, maintained a vegetable garden. Such gardens not only provided vegetables to be eaten fresh during the summer but also to be preserved for use during the winter months. Green beans and tomatoes were canned; cabbage made into sauerkraut and cucumbers into pickles. Potatoes were dug and placed in a cellar for winter storage. As it turned out, produce from our garden helped feed our family all year long.

Unlike forests and prairies, vegetable gardens aren't natural occurrences. Vegetable gardens are human creations. Someone has to till the soil, plant the seeds, set the plants and pull the weeds. And contend with insects that are sure to arrive and chow down on the leaves of the plants.

The garden was a good place - in those days as it is today - to give kids a job to do. Years ago my garden job was what we would today call a pest management specialist. I got to remove weeds and insects from the garden! Back then we didn't have herbicides and insecticides, so weed control was through the use of a hoe. Insect control was also a mechanical approach - physically picking insects off affected plants.

The two most memorable targets of my insect removal efforts were the tomato hornworms and the potato beetles. To be sure, other insects occasionally wreaked havoc in our garden by sucking plant juices or by infecting plants with a disease organism. But it was the leaf destruction caused by these two plant chewers that was the target of most of our insect-control efforts.

The potato beetles always showed up first, around the end of May. Many people call these striped beetles potato bugs. While they are insects, they are not true bugs, such as stink bugs. They are beetles - Colorado potato beetles to be exact! As their name suggests, these insects were first discovered in Colorado and feed on potatoes or other related plants, such as eggplant.

Colorado potato beetles spend the winter in hibernation as adults. When the growing season arrives the beetles search for a host plant, where eggs are deposited. My job was to catch and destroy the beetles. I also looked for the yellow egg masses on the underside of the leaves and destroyed as many as I could find. But many hatched, and the immature beetles began to do what they do best - eat potato leaves. At this point I would pick off the immature beetles.

I had three approaches to getting rid of the unwanted insects. The first option was to merely squeeze the insect to death between my fingers. This approach was somewhat messy as the smashed insect turned your fingers an orange color. A second control technique was to drown the insect in a can of water. Potato beetles and their larvae are not good swimmers. On occasion, I would throw the immature insects away from the potato patch. I just assumed the wingless creatures wouldn't make it back to the potatoes.

A bit later in the season I would turn my attention to the tomato plants and begin looking for hornworms. Always it seems hornworm caterpillars would show up and literally overnight devour a batch of leaves before I discovered they were present. These insects are called hornworms because they have a horn-like projection on their rear. One of the misconceptions about hornworms is that they can sting with the horn. They can't. That horn is just a decoration!

For me, the best approach to killing hornworms was to do the caterpillar stomp. Throwing the big worm to the ground and applying a bit of shoe leather seemed to be a suitable method for dispatching the pest. Years later I learned that tomato hornworms turned into hummingbird moths that sip nectar from flowers. Which just goes to show that even a garden insect pest can sometimes have a good side!

 

Writer: Tom Turpin
Editor: Olivia Maddox