Pillars Fall to Poison Pill
Packaging a natural virus in an otherwise appealing "poison pill"
tricks destructive caterpillars into eating themselves to death. The trickery
offers a natural way to control larvae of beet armyworms, cabbage loopers, and
other moth pests. Normally, farmers combat them with chemical insecticides. But
ARS scientists envision killing them with a natural insect pathogen. The
nuclear polyhedrosis virus liquefies the pests'
tissues, while posing no threat to beneficial insects, humans, or wildlife.
Researchers want to ensure that the pests get a lethal dose, so they are
testing combinations of virus and feeding stimulants. One concoction contains
cottonseed oil, sucrose, and other goodies irresistible to caterpillars like
beet armyworms that pester corn, cotton, and cole crops.
In the greenhouse, scientists sprayed collards with virus alone and mixed with
a feeding stimulant. Virus alone killed 57 percent of the larvae, but adding
the feeding stimulant doomed more than three-fourths. In other tests,
scientists sprayed formulations containing fluorescent brighteners. These help
prevent light from degrading the virus and improve its capacity to infect the
pests. Only one-fourth of armyworms survived on foliage collected from outdoor
collard plots sprayed with virus and brightener. Twice as many survived when
the brightener wasn't used. The scientists plan tests combining all three
ingredientsvirus, feeding stimulant, and brightener.
Robert Farrar, Jr.
, Beltsville, Maryland; phone (301) 504-5689.
With New Tomatoes, More Is Beta (Carotene)
Three new tomato breeding lines from ARS hold 10 to 25 times more beta carotene
than typical tomatoes. An ARS plant geneticist bred the new tomatoesnamed
97L63, 97L66, and 97L97for use in processing into paste, juices, and
sauces. High-beta-carotene cherry and beefsteak tomatoes for the fresh market
are also on the way. The body converts beta carotene to vitamin A. This
essential vitamin helps with vision, bone growth, tooth development, and
reproduction. Content of beta carotene averages 57.6, 55.1, and 55.5 micrograms
per gram of fresh fruit for 97L63, 97L66, and 97L97, respectively. This
compares to only about 2 to 5 micrograms per gram for typical tomatoes. Lines
97L63 and 97L66 are adapted for California and Eastern and Midwestern states;
line 97L97, for the East and Midwest. A major food company is using material
derived from the ARS germplasm to develop nutritionally enhanced products.
Beltsville, Maryland; phone (301) 504-5583.
Corn Fungus Also Has a No-Good Cousin
ARS scientists have discovered a cousin of the fungus that causes gray leaf
spot of corn. This means breeders must now ensure that new corn hybrids resist
both forms of Cercospora zeae-maydis
. A severe infection can reduce corn
yields by 25 percent or more. The fungus first turned up in this country in
about 1925 in Illinois. But it didn't become a serious and widespread problem
until the mid-1980s, when more and more farmers switched to tillage systems
that leave crop residue on the soil surface. That's because C.
can overwinter in this residue. In spring, the fungus produces
spores called conidia. Blown by wind or splashed by raindrops, the conidia land
on leaves of newly emerged corn plants, invade, and attack the plants' tissues.
The invasion may also make the plants weaker and more susceptible to infection
by other pathogens. Once a problem only in the eastern part of the Corn Belt,
gray leaf spot now occurs as far west as Kansas and Colorado. An ARS plant
pathologist found the new form of C. zeae-maydis
in the eastern part of
the country. Scientists are probing its genetic makeup to learn more about its
Larry D. Dunkle
Production and Pest Control Research Laboratory
, West Lafayette, Indiana;
phone (765) 494-6076.
New Lure Could Take the Sting Out of Some Wasps
An ARS entomologist has devised the first effective lure for the German
yellowjacket, golden paper wasp, European hornet, and other yellowjackets.
Commercial traps could be available in about a year. Yellowjackets and wasps
are occasional nuisances for most people, but they represent an occupational
hazard for fruit orchard workers during the picking season. Besides hurting,
the stings can cause potentially dangerous allergic reactions. The new
attractant may provide a way to monitor and control the insects. It uses
compounds that bacteria and fungi make as byproducts of sugar consumption. ARS
has applied for patent protection. Other baitsmade with sugar or
meathave drawbacks. Sugary baits attract beneficial species, such as
honey bees. As for meat, it rots too quickly to be practical in a lure. Of 17
yellowjacket species in the United States, 5 are significant, aggressive pests.
The new lure is the first to attract most of them, including the German
yellowjacket. It is also the first chemical lure to attract paper wasps. The
scientist and Sterling International, Inc., of Veradale, Washington, are
collaborating to develop a delivery system. The work is being carried out
through a cooperative research and development agreement.
Peter J. Landolt, USDA-ARS
Yakima Agricultural Research
Laboratory, Wapato, Washington; phone (509) 454-6551.
"Science Update" was published in the
February 1999 issue of
Agricultural Research magazine.