Detached Antennae Tell What an Aphid Can
Looking over the menu of plants growing in a typical field, how does an
aphid decide which crop to feed on?
Plant colorparticularly yellow and greenhas long been
established as one stimulus. Another, scientists now confirm, is the odor
coming from the plant.
How do they know this? An Agricultural Research Service scientist snipped
off the aphid's antennae to detect the odors appealing to the pest. Among the
favorites are the so-called green-leaf odorsthe dominant smell of cut
It's an important finding for scientists trying to understand the behavior
These crop-damaging pests suck juices from a wide variety of plants. They
also spread harmful plant viruses as they feed.
Understanding how an insect perceives its world and how that perception
affects its behavior is one of the first steps toward preventing its damage to
Over the last 4 years, studying the pea aphid's sensitivity to plant odors
has been the job of Wilant van Giessen. He's a graduate student from the
Department of Entomology of Wageningen Agricultural University in The
Netherlands. Working under a cooperative research agreement between ARS and
Clemson University, he is studying the basic behavior of aphids as part of an
overall effort to find new ways to control the pests.
Based at the U.S. Vegetable Laboratory operated by ARS in Charleston, South
Carolina, van Giessen is an expert in electroantennographythe science of
measuring what an insect smells through the antennae that serve a function
similar to that of the human nose.
To detect what an aphid smells, van Giessen cuts off an antennaonly 2
millimeters longand attaches tiny electrodes at each end. These minute
glass lubes are filled with a salt solution to conduct an electrical current.
Then he exposes the antennae to different plain odors, recording and
analyzing results that look on a computer screen like an electrocardiogram.
It's all done under a stereo microscopeand it must be done quickly. Once
an antenna is cut, it only retains its sensitivity for 20 to 30 minutes, at
And there are other things that can throw off the results. "When I
conduct these experiments I make sure they arent cutting the grass
outside the lab," van Giessen says.
Van Giessen is now studying whether winged aphids are more sensitive than
wingless ones to plant odors. "We think that in general, they are more so,
because their primary job is to find a new plant on which their offspring can
feed," van Giessen says. "Wingless aphids concentrate more on feeding
and reproduction, rather than moving from plant to plant."
Van Giessen says he has used the pea aphid as a model system because it is
larger than most aphids and feeds on a variety of crops besides peas. But he
has also studied other aphids, including green peach and potato aphids, and he
plans to work on the birch aphid, which feeds only on birch trees. By
Sean Adams, ARS.
Vegetable Laboratory, 2700 Savannah Highway, Charleston, SC 29414; phone
"Detached Antennae Tell What an Aphid Can
Smell" was published in the
January 1995 issue
of Agricultural Research magazine.