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What's the best time to attack the sweetpotato whitefly strain plaguing
southwest cotton? When there are an average of 1-1/2 sweetpotato
whitefly nymphs per square inch on cotton leaves. Nymphs, an immature
stage of the pest, are most vulnerable to chemicals. Holding off
insecticide spraying until nymph density reaches 1-1/2 per square inch
allows growers to minimize chemical use and whitefly damage. The new
whitefly strain, also known as silverleaf whitefly, has caused more than
$200 million damage annually to U.S. crops since 1991. Besides cotton, it
attacks dozens of vegetable and ornamental crops mainly in Arizona,
California, Florida and Texas.
Western Cotton Research
Laboratory, Phoenix, AZ
Thomas J. Henneberry, (602) 379-3524
Up to 80 percent of the sticky sugars that sweetpotato whiteflies deposit
on cotton bolls can be removed by enzymes sprayed on the crop during
harvest. Growers get a lower price for sticky cotton because the
sugars gum up machinery in cotton gins and textile mills. But ARS
researchers found and tested the new use for the enzymes, which are
already commercially available. Scientists say the whitefly strain that
has plagued southwest farmers in recent years can produce more than 500
pounds of contaminating sticky sugars per acre.
Western Cotton Research
Laboratory, Phoenix, AZ
Donald L. Hendrix, (602) 379-3524
When Mediterranean and Mexican fruit flies eat a blend of red and yellow
dye, the insects perish after a few hours in the sun. ARS scientists
in Hawaii and Texas are building on results from their early lab and field
tests. They want to know if the dye blend might replace malathion, the
chemical insecticide used in sprays and baits to quell fruit fly pests of
citrus and other crops. The blend, called SureDye, is a product of
PhotoDye International, Inc., Linthicum, MD. The dyes, Red 28 and Yellow
8, are registered by the Food and Drug Administration and used in drugs
and cosmetics. Since malathion kills pests on contact, it may kill
beneficial insects such as honey bees. By contrast, the red dye must be
consumed. Then, activated by light, it apparently breaks down membranes,
such as those found in the gut tract, killing the insect. ARS has asked
the Environmental Protection Agency to approve large-scale field tests.
ARS and PhotoDye have filed patent applications on SureDye technology.
Scientists at other ARS locations are investigating SureDye's potential
against other pests such as boll weevils and corn earworms. (PATENT
APPLICATION 08/353,726)
Crop Quality and Fruit
Insects Research, Weslaco, TX
Robert Mangan, (210) 565-2647
Tropical Fruit and Vegetable Research Laboratory, Hilo, HI
Roy Cunningham, (808) 959-4300
Spreading starch granules laced with malathion cut insecticide levels
99
percent without sacrificing corn earworm control. In field tests, ARS
researchers treated corn with 10 pounds per acre of granules laced with
one-tenth of a pound of malathion. Control was as effective as if 100
times that much malathion had been sprayed. The reason: Starch granules
stick to plant leaves, so the pesticide is concentrated precisely where
needed and lasts longer. Corn earworms cost U.S. corn growers about $1.5
billion annually in crop damage and chemical controls. Researchers are
adapting the technology for wide-scale application, so farmers can use
it.
Plant Polymer and Mycotoxin Research,
Peoria, IL
Michael McGuire/Patrick Dowd, (309) 681-6222
The boll weevil's "sweet tooth" helped scientists breed cotton that's too
"bland" for it. A female weevil tastes a cotton bud to gauge whether
it's rich in sugars her larvae need to grow. If the sweetness meets her
exacting standards, she'll lay an egg in the bud. To discourage her, ARS
scientists have bred low-sugar cotton germplasm lines. In 1990 and 1993
field tests, the new lines had only about half as many eggs as commercial
varieties. The "low sugar" genes in the new lines originated from
primitive Mexican and Central American cottons. Cotton breeders could
develop the new lines into high-yielding, commercial varieties.
Cotton Host Plant
Resistance, Mississippi State, MS
Jack C. McCarty/Paul A. Hedin, (601) 323-2230
Bacterial toxins delivered via biotechnology could become a nemesis to
banded sunflower caterpillars that gnaw sunflowers on the Northern Great
Plains. ARS scientists found young banded sunflower caterpillars more
vulnerable than older larvae to Bacillus thuringiensis (Bt) toxins.
As genetically engineered corn, cotton and potatoes with insecticidal Bt
genes near commercialization, researchers anticipate similar
transformation of sunflowers to resist insect pests.
Oilseeds Research, Fargo, ND
John F. Barker, (701) 239-1278
A new atlas of pollen grains from nearly 400 species of flowering plants
will help track the travels of devastating migratory crop pests such as
the corn earworm. This information can help growers stop pests at
their source before they spread and wreak damage over a wide area.
Researchers can check pollen grains taken from insects' bodies to pinpoint
where the pests foraged before they began wandering. As part of a massive
area-wide pest management study based in Texas, ARS and university
scientists in 1990 began compiling a scanning electron picture atlas that
depicts magnified whole pollen grains. Each species of flowering plants
makes its own distinctive-looking pollen grains, so the grains can be
vital clues to determining where a migratory pest originated. Previous
pollen guides showed grains "by the slice," making it difficult to
identify whole grains found on captured insects. So far, the new atlas
identifies pollen of 398 plant species in the southern United States.
Areawide Pest Management
Research, College Station, TX
Gretchen D. Jones, (409) 260-9351
Last updated: November 15, 1996
Return to: Quarterly Report
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