Netting A Solution to Aphids

By Eve Pranis

No question about it, say fifth graders in Casselberry, FL. Aphids, in fact, really do suck. Frances Guest's gardening club had worked hard raising scads of native milkweed plants to nourish Monarch butterfly larvae. But when they checked for Monarch eggs near leaf tips, they discovered that aphids, who also love tender young growth, had all but sucked the milkweed dry.

"The kids were upset about the damage," says Frances. However, when a father suggested they use a chemical spray, the children, united, appealed, "No, you'll kill our Monarch eggs!"

"Together we brainstormed what we could do to rid our precious plants of the aphids," says Frances. "The students tried rinsing the leaves with cold water, spraying them with soapy water, and squishing them, but after a week or two, it hadn't made much difference." Then a student recalled reading that lady beetles were brought here from Australia to control a particular cotton pest. Class research revealed that lady beetles also find aphids a culinary delight. And the hunt was on.

"We decided to buy 1,000 lady beetles from a local source, but when we released them near the milkweed, most of them flew away," says Frances. The sun, her class discovered, releases a hormone in lady beetles that actually triggers flight. Frances' young scientists returned to trying mechanical solutions, but were still losing the aphid battles. Finally, they hit on another solution. If they couldn't keep the aphids out, why not try keeping lady beetles in? "Two girls suggested using some inexpensive netting (as light as bridal veil material), to keep the lady beetles trapped near our milkweed," explains Frances. "So the class experimented with 12 plants by laying squares of netting over every plant or two, then tying them loosely at the bottom with yarn." A new batch of beetles in hand, students put at least two dozen per plant under the netting, then watched the drama unfold in what they christened "the ghost garden." And what a show it was.

"The students observed their experimental plants with and without magnifiers and used journals to draw and write about their discoveries," says Frances. "They witnessed the adult beetles devouring aphids and also predicted what would become of the eggs they laid." A big "aha" for the students, explains Frances, was that most aphids were actually consumed by the lady beetle larvae, which they decided looked like little alligators. Within just two weeks, most plants appeared aphid free, so the students lifted the veils. "Some adults and larvae remained in the area, but most moved on," says Frances.

Spreading the Word and the Lady Beetles

News of the students' Monarch and milkweed habitat and chrysalid business made its way to Casselberry city planners, who invited students to set up an exhibit at a city environmental and cultural fair. "The students wanted to display habitat elements and share what they'd learned about Monarch habitats and migrations," says Frances. So they designed a booth that featured photos and descriptive posters of their Monarch butterfly migration project, plants with live Monarch caterpillars and chrysalids, nursery-donated butterfly nectar plants, and yes, lots of aphids and lady beetles.

The young habitat stewards wanted to encourage others in the community to raise milkweed for Monarch larvae, too, so they filled 1,000 sandwich bags with milkweed seeds they'd gathered. Next, students created brochures explaining milkweed's role in the Monarch life cycle and describing how to plant and care for it. Their next challenge: How to spread the word about the value of lady beetles for keeping pest populations in check? First, a display. A few weeks before the fair, the kids decided to snip off aphid-infested tops from milkweed plants, then place them in water in a plastic aquarium along with some lady beetles. They predicted that containers filled with delightful predators eating pesky prey, along with explanatory brochures, would draw visitors' attention.

But the class wanted to do more than just inform; they wanted to inspire action. So they decided to give away lady beetles. "For $15, we bought 3,000 lady beetles and kept them hibernating in the fridge for a few days," says Frances. Then, just before the city fair, the class turned off all lights and cranked up the air conditioner (so the ladybugs wouldn't be prone to fly), then prepared to pack them up. "We bought small plastic cups with lids, then set up a system in which each student prepared 15 cups by putting in one raisin (from which adults can suck moisture) and making three holes in the lid," explains Frances. "I poured a batch of lady beetles into a baggie for each child, then they placed them into cups and put on lids. We repeated this process until, within 2 hours, we had 1,000 cups ready to give away." The students created a small sheet on how and when to release lady beetles (in the evening) and included a picture of their ingenious netting system. "Even if they do fly away," read the instructions, "somewhere they will still help out by eating aphids!"

How They Grew

"I wasn't into butterflies myself, but I wanted something that would interest the kids," says Frances. They all learned a lot in the process. Frances, for instance, learned even more about the value of following her students' lead, letting them take charge of their learning. Sure, they learned about food chains, habitats, and other science concepts, but Frances explains that she hadn't anticipated just how much else they would gain. "The kids felt pretty special running their popular booth and tent alongside mainly adult exhibitors," explains Frances. "The city was so impressed that they donated eight oak trees to plant on campus. The students had to use what we had at hand to solve problems and try new ideas if their initial ones failed," she adds. "And they came up with such novel ideas and unique ways of using materials. Adults tend to want to do it the way they've always seen it done."

Meet the Beetles

Although we know them as ladybugs, these familiar garden denizens, which inevitably inspire curiosity and questions, are not actually bugs, but beetles, and they are not all ladies! (True bugs constitute a different group, or order, of insects, characterized by broad, flat bodies with triangular designs that are formed by overlapping wings.)

Encourage students to look for signs of lady beetles in the spring garden. They may find yellow clusters of eggs on leaf undersides or lady beetle larvae, which resemble tiny humpback alligators. These youngsters feed voraciously on little creatures, such as aphids, and grow quickly. Each larva sheds its skin (molts) three to four times as it grows (during one to five weeks), then glues itself to a safe spot, such as a leaf, and becomes a pupa in a hard shell. After a week or two, an adult lady beetle emerges and eats mainly aphids and scale insects (up to 100 each day!). Some predators might starve if they were so limited in food choices, but it's no problem for these beneficent beetles. During the summer, female aphids produce only female babies who are born with their own tiny babies inside them! So as a lady beetle cleans off aphids, there are scads of replacements -- and the natural balance is sustained.

If you order lady beetles from a science supply catalog, you can store them for up to two months in the fridge. Spritz them with water once a week while they're in storage. Since they don't fly at night, try releasing them near dusk. Some insectaries suggest spraying them lightly with a solution of 1 part water to 1 part soda to keep their wings sealed for a week or so. It can be a challenge to entice them to stick around, as the Casselberry students discovered.

As your curious students examine ladybeetles and their behaviors, have them generate questions -- Will lady beetle larvae move toward aphids? How high can a lady beetle climb? Do they prefer some garden plants to others? -- then categorize them into ones they can answer through further observations, experiments, research, or interviews with experts.

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