- Important insecticides from plants
- rotenoids - New World and now Asia
- pyrethrins - Near Eastern center
- tobacco - New World
CHAPTER 13 IN THE TEXT, and lecture material
Many insecticidal compounds are known from plants. Most plants make defensive compounds called
allomones. Few are important commercially. Plant-derived insecticides have largely been replaced
by synthetic materials, but there are some advantages to the
naturally occurring materials. For example, these substances are biodegradable. Selectivity is
needed. Compounds that are toxic to insects, but not toxic to mammals, are preferable, of
A series of compounds found in members of the genera Derris, Lonchocarpus,
Tephrosia(and in Amorpha-- although that's never been exploited) are known as
rotenones. We discussed them
previously, as they have been used in "primitive" cultures as fish poisons. Commercially, rotenoids
are isolated mostly from the roots of Derris ellipticain Indonesia and from Lonchocarpus
in South and Central America. These compounds are isolated by grinding the plant and extracting with
solvents such as hexane or petroleum ether or chloroform. The compounds are oil soluble or lipids.
They make up 1-20% of the dry weight of the roots.
Another major series of compounds, the pyrethrins, come from species of the genus Chrysanthemum (some
people put these species in Pyrethrum) (Asteraceae or Compositae). These were used as
far back as the 1st century B.C. by the Chinese. Insecticidal plants mostly are grown in countries
with inexpensive labor and high elevations such as Kenya and New Guinea. The flower heads contain
about 3% crude pyrethrins. The compounds are extracted with lipid-like solvents just as rotenoids
above. These plant derived compounds are the major ingredients of many household insecticides.
Often synergists (compounds not active themselves, but they enhance the activity of the
insecticide) are added.
Pyrethin producing Chrysanthemum species
Other plant derived insecticides
Ryania (Flacourtiaceae) is also used occasionally. Haplophyton cimidium (Apocynaceae)
is the cockroach plant of Mexico. Tobacco (which contains nicotine) is another major source of
insecticides. Nicotine especially effective against aphids.
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Fish Poison notes
Revised April 2005
© David S. Seigler, Integrative Biology 363, Plants and Their Uses,
Department of Plant Biology, 265 Morrill Hall, 505 S. Goodwin Ave., University of Illinois, Urbana,
Illinois 61801, USA. 217-333-7577. email@example.com.