Of all the rude things a lady can do, eating her guests tops the
list. Offering visitors
less than their favorite snacks isn’t too sociable, either.

But that’s what the Scymnus beetle does to aphids and fire ants.
The tiny lady beetles’
behavior makes them welcome in cotton farmers’ fields.

“It’s a good little predator, even though it’s very small,” said
John Ruberson, a
University of Georgia research entomologist. “We’re working to
learn how much insect
control the Scymnus provides.”

The Scymnus is a type of ladybug. Only about one-third the size
of other ladybugs,
adults are only an eighth of an inch long. They aren’t even big
enough to have spots.
But they eat caterpillar eggs and aphids that can damage crop
plants, particularly
cotton.

All ladybugs are beneficial. But at Ruberson’s labs on the
Tifton campus of the UGA
College of Agricultural and Environmental Sciences, he and
graduate student Andrea
Southworth have found something special about the Scymnus.

During the larval stage, the Scymnus produces a waxy substance
from glands on its
back. “We’re not sure exactly what it does, but the fire ants
don’t like it,” Ruberson
said.

The waxy substance protects the ladybug larvae from the ants,
allowing ladybugs to
multiply quickly in the field.

Fire ants usually kill ladybugs to protect the aphids the
ladybugs feast on. Fire ants
“farm” aphids for their honeydew, a sweet liquid aphids produce
from plant juices.

Ruberson said Scymnus beetles can help farmers, particularly
those growing cotton in
reduced-tillage fields.

Jimmy Dean, an agronomist with the National Resources
Conservation Service, said
about 12 percent, or 162,000 acres, of Georgia’s 1.44 million
acres of cotton is in
reduced tillage systems.

Ruberson and Southworth are working to learn the ladybugs’
impact in a field.

“As soon as we learn how many eggs and aphids a certain number
of the Scymnus eat,
we’ll be able to find how much insect control they’ll provide in
a field,” he said.

Natural insect control can cut in half the number of sprays
farmers use to fight
crop-damaging insects.

That can be especially important during dry years. During wetter
years, Ruberson said,
fungi and diseases help control aphid and caterpillar
populations.

Scymnus ladybugs can help indoor farmers, too. “They may be
especially helpful in
greenhouses where aphids multiply quickly,” he said. But they
aren’t easy to raise for
commercial use.

“We know what they like to eat in the field,” he said. “But we
haven’t found a lab diet
they like and will thrive on.”

Ruberson said they’re about three years from making a prediction
about how many
ladybugs will provide insect control in the field. But recently,
he notes, Scymnus
populations have increased and expanded across Georgia and as
far west as Texas.

“No matter how many are out there,” he said, “these numbers
can’t do anything but
help us.”