Theme: Gardening
for a Sustainable Future
Netting A Solution to Aphids
Fifth
Graders Host Hostage Lady Beetles
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
|
lady beetle
|
adult |
larva
|
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.
true
bug |
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