Assume your eagle-eyed classroom observers notice a collection of those sucking little pests, aphids, on the leaves and stems of your classroom garden plants. What should you do? The horticultural guide, GrowLab: A Complete Guide to Gardening in the Classroom, will tell you not to worry -- (a.) pesky pests won't necessary spell the end of your indoor garden plants, and (b.) you can control aphids to a point using a soapy water spray or wash.
We've heard from a couple of educators around the country who have taken yet a third approach. They've turned the appearance of garden pests into a wonderful opportunity to observe and learn about food chains, and plant/animal and predator/prey interactions. Increasingly, commercial greenhouse growers, homeowners, and farmers are taking advantage of existing natural relationships and using "beneficial" insects to control garden pests. Although timing, life cycle stages, and environmental conditions must be right (and this can be a challenge), introducing beneficial insects can provide an exciting science focus for your class.
Ladybugs -- aka "Aphid Wolves"
Sharnell Jackson, a third grade teacher in Chicago, told us that she had actually imported aphids from a science supply catalog, as part of a plant and animal populations unit. When the aphid population exploded and threatened GrowLab plant health, the class ordered ladybeetles as well.
Who would believe that the cheerful, gentle ladybug (technically, not a bug, but a beetle) will eagerly eat more than 5,000 aphids (along with white flies, mites, and indoor garden pests) during its year-long life?! Ladybeetle larvae, in fact, known to eat as many as 40 aphids per hour, have earned the nickname "aphid wolves."
"Students were fascinated," said Sharnell, "to explore and experiment to see what the ladybeetles preferred to eat. We kept them in small vials and added different types of aphid-covered leaves. When we let the ladybugs out in the GrowLab, they first stayed on the plants, but tended to fly to the windows as the food supply dwindled. The kids really gained an understanding of food chains, and how we can mirror nature to protect our plants without using harmful chemicals."
Enthusiastic gardeners have sometimes released ladybugs as predators only to have them fly off and disappear. To improve the chance that your ladybugs have been collected at the stage when they're hungriest, consider ordering them from a science supply catalog or a company specializing in beneficial insects. As wild creatures, ladybugs will leave if they don't like their new environment. If they have no way out, they'll tend to collect around the windows and die. The following suggestions will encourage ladybugs to stick around your classroom:
Of course, aphids aren't the only pests that ladybugs will eat. Your students will no doubt have plenty of questions and make lots of discoveries should you lunch with ladybugs. We're eager to hear about your experiences.
Catching Your Own
If you choose to catch your own ladybugs, it's best to bring in young beetle larvae in the spring from the garden. Resembling alligators, the tiny black larvae emerge from clusters of yellow eggs attached to leaf undersides. After feeding for a few weeks, a pupa (black with red markings) forms on the upper leaf surface. In five to seven days, an adult emerges.
Visit the following Web site for information on ordering ladybugs and other beneficial insects: www.gardensalive.com