Caterpillars—Agents of Their
Own Demise
Many plants produce repellent compounds to protect themselves from hungry
insects. But researchers have found that certain species of caterpillars elicit
from plants specific chemical aromas that also lure natural enemies of the
pests. In other words, the feeding of the caterpillars stimulates release of a
plant chemical that summons their predators. These predatory insects, often
wasps, lay eggs that hatch into larvae, which then consume their caterpillar
hosts.
Until now, researchers have assumed that release of these
“herbivore-induced” plant chemicals occurs mainly during the day. But
studies have shown that test tobacco plants release the chemicals during the
day and night, with some produced mainly at night.
The chemicals elicited were found to be highly repellent to moths searching for
egg-depositing sites. The substances signaled to the pests that the crop was
infested with predator larvae, thus sending the moths on to other locations.
Consuelo M. De
Moraes, USDA-ARS Center for
Medical, Agricultural, and Veterinary Entomology, Gainesville, Florida;
phone (352) 374-5712. Bean Plants Repel Nematodes
Incorporating the dried plant material of several unusual types of beans into
the soil may reduce the number of root-knot nematodes dwelling there, an
ARS study suggests. These minute
roundworms in the soil cause yield losses and control costs of $53 million
annually in the South alone.
When dried parts of little-known legumes like coffee senna, sun hemp, and jack
beans were mixed into potting soils, scientists got reductions as high as 89
percent in the number of nematode galls on the roots of test tomato plants.
This nematicidal activity has been attributed to natural substances produced in
the plants' seeds, stems, and leaves.
Hundreds of semitropical legume species belonging to 64 genera and collected
from around the world are being maintained in ARS' Plant Genetic Resources
Conservation Research Unit. Many of these could have multiple uses—from
curbing erosion and controlling weeds to yielding pharmaceutical compounds for
drugs.
Brad Morris, USDA-ARS
Plant Genetic
Resources Conservation Research Unit, Griffin, Georgia; phone (770)
229-3253. Unlocking the Keys to Cockroach Resilience
The German cockroach—Blattella germanica—one of the world's
most intrusive species, likes to live indoors with us. And it appears to be
increasingly unphased by common insecticides.
Scientists have been studying certain strains of B. germanica to see how
they develop pesticide resistance. They've discovered that several strains have
a unique, membrane-bound protein called esterase, which detoxifies some
insecticides. Roaches with the enzyme can withstand a whole lot more
insecticide than their unprotected relatives can.
Another key mechanism responsible for roach persistence pertains to what's
called knockdown resistance, or kdr. This is caused by mutations in
nervous system proteins of some insects. Researchers have identified a gene
mutation associated with kdr in 83 percent of German cockroach field
populations surveyed. And they've also found two new mutations that make the
roaches more resistant to pyrethroid and related insecticides.
Steven M. Valles,
USDA-ARS Center for Medical,
Agricultural, and Veterinary Entomology, Gainesville, Florida; phone (352)
374-5834. Everything You Wanted To Know About Food Safety
Do you ever wonder what the government's doing to address food safety problems?
Or what research projects the government's supporting? Or what that investment
is actually accomplishing?
Now there's a single place to find answers to those questions and many others.
A new web site has been created by the National Agricultural Library's Food
Safety Research Information Office in Beltsville, Maryland. The site includes
food safety news; information about research projects, spending, and
accomplishments; and over 100 links to web-based food safety research
information provided by U.S. and foreign governments and educational and
professional organizations.
The searchable database offers information on nearly 500 food safety research
projects dating from 1998. It is a tool for scientists and policymakers to use
in determining research needs and setting priorities in food safety.
The database is also a valuable resource for interested members of the general
public. To access and use the database, go to
http://www.nal.usda.gov/fsrio.
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