Protecting gardens and crops from insects using the `smell of fear'


Date:
August 25, 2021
Source:
American Chemical Society
Summary:
For home gardeners and farmers, herbivorous insects present a major
threat. The predator insects that feed on these bugs emit odors that
pests can sense, which changes the pests' behavior and physiology to
avoid being eaten. With bugs becoming more resistant to traditional
pesticides, researchers now report they have bottled the 'smell of
fear' produced by predators to repel and disrupt insects naturally.



FULL STORY ==========================================================================
For home gardeners and farmers, herbivorous insects present a major
threat to their hard work and crop yields. The predator insects that
feed on these bugs emit odors that pests can sense, which changes the
pests' behavior and even their physiology to avoid being eaten. With
bugs becoming more resistant to traditional pesticides, researchers now
report they have developed a way to bottle the "smell of fear" produced
by predators to repel and disrupt destructive insects naturally without
the need for harsh substances.


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The researchers will present their results today at the fall meeting of
the American Chemical Society (ACS).

"It is not uncommon to use our senses to avoid risky situations. If a
building was on fire, we as humans could use our senses of sight or smell
to detect the threat," says Sara Hermann, Ph.D., the project's principal investigator. "There is evidence for such behavioral responses to risk
across taxa that suggest prey organisms can detect predation threats,
but the mechanisms for detection aren't very well understood, especially
with insects." "Insects rely on olfactory cues to find food, mates and
places to live, so this is a great opportunity to investigate how to
use these smells to manipulate their behavior," says Jessica Kansman,
Ph.D., a postdoc who is presenting the work at the meeting. Hermann and
Kansman are at the Pennsylvania State University.

Aphids are a highly destructive pest to an array of crops, and their large numbers, ability to transmit plant pathogens and increased resistance
to insecticides make them a persistent problem for growers. They also
happen to be a favorite food of the ladybug, which gardeners welcome as
a source of sustainable pest management. Hermann's research has shown
that aphids and other herbivorous insects will steer clear of fields and gardens if they can smell predators nearby. Not only that, but exposure
to the odor cues given off by ladybugs can also cause aphids to slow
their reproduction rates and increase their ability to grow wings,
both of which are behaviors designed to avoid threats.

With these observations in mind, the research team set out to determine
whether the olfactory cues given off by ladybugs could, by themselves,
control pests.

They started by identifying and extracting the volatile odor profile
from live ladybugs using gas chromatography -- mass spectrometry, which separates and allows for identification of the individual components of
the ladybugs' smell.

To see which compounds the aphids would respond to, they hooked up the
antennae of live aphids to an electroantennogram (EAG) machine and exposed
them to each individual odor the predator emitted to see which compounds
they detected. The strength of their reactions was measured based on the
signal picked up by the EAG machine. Of the many compounds emitted by
ladybugs, aphids had the strongest response to methoxypyrazines, such
as isopropyl methoxypyrazine, isobutyl methoxypyrazine and sec-butyl methoxypyrazine. Once the compounds were identified, Hermann and team set
out to create a special odor blend that can be used in an essential oil diffuser that will spread the scent over time across a garden or field.

Next, the team plans to conduct field tests of their scent diffusers
to see if the effects on aphids and ladybugs are similar to what they
observed in the lab. Hermann and Kansman also want to determine the
dispersal area of the diffusers, and whether they could be applied to
other pests and predators, as well as various types of crops. In addition,
they are collaborating with a manufacturing company to design special
diffusers for eventual commercial use by both farmers and gardeners.

========================================================================== Story Source: Materials provided by American_Chemical_Society. Note:
Content may be edited for style and length.


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Link to news story: https://www.sciencedaily.com/releases/2021/08/210825142917.htm

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