Spudman April 2023 - 28

The Potato Association of America mission statement: The PAA and
its allied associations must strongly support the private sector through
Extension, research and commercialization efforts aimed at enhancing
the role of the potato as the premier food source for the 21st century.
Emergence of elicitors
A potential new tool in the pesticide toolbox
By Silvia I. Rondon
and Alexander Butcher
Oregon State University
T
he concept of integrated
pest management includes
environmentally sustainable
and economically effective approaches
to control pests that rely on a complex
combination of a series of control
options. Those control options include
breeding, monitoring, cultural,
physical, biological, biorational and
chemical practices.
Chemical control is an important
part of pest management programs;
however, pesticides can cause problems
if not used correctly. Problems can
include pesticide residues, crop damage,
reducing biological control populations
or decreasing the quality of human
and animal health while damaging the
environment (Figure 1).
In the literature, there are several cases
of insects, weeds and diseases developing
resistance to pesticides. In the insect
world, one of the most famous cases of
resistance is that of the Colorado potato
beetle (Figure 2). To make the story short,
it is well documented that the Colorado
potato beetle is responsible for the
development of the insecticide industry.
Impressively, in some documented
cases, this insect has broken a mode
of action after one year in the market
(e.g., endrin) or even during the first
year of use (e.g., oxamyl) (Figure 3).
Now, the Colorado potato beetle
population in the eastern part of the
U.S. has developed resistance to all
modes of action, in some cases in a
very short time frame.
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Spudman * April 2023
Figure 1: Pesticides are an important component of pest management programs but
can cause problems if not used correctly. Photos: Oregon State University, Irrigated
Agricultural Entomology Program
The first case of resistance to
synthetic organic pesticides was
observed for DDT in 1952, followed by
dieldrin in 1958, and other chlorinated
hydrocarbons. In following years,
the beetle developed resistance to
numerous organophosphates and
carbamates. Currently, the Colorado
potato beetle is resistant to arsenicals,
organochlorines, carbamates,
organophosphates and pyrethroids.
The major problem area for
resistance is the northeastern U.S.;
however, resistance has also been
detected in other areas of the country,
including the West, as well as in
Canada, Europe and Asia.
INTRODUCING ELICITORS
Elicitors are chemical compounds
that induce the plant's immune system.
They are classified as pathogen-derived
or exogenous elicitors and plant-derived
or endogenous elicitors. In other words,
some are induced by external factors
and others are not.
In a cascade of biochemical
reactions, elicitors trigger signals in
plants, predominantly resulting in
the upregulation of phytohormone
systems. The principal phytohormone
system in plant-biotic interactions
are the jasmonic acid (JA), salicylic
acid (SA), and ethylene system. These
phytohormones can occur naturally in
Spudman April 2023

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