Theme: Nurturing Young
Scientists
Netting a Solution to Aphids
Fifth Graders Host Hostage Lady Beetle
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.
Author: Eve Pranis
© 2008
National Gardening Association