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Science Update
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Spraying Fruit Trees to a "T"
Field tests show the effectiveness of a new T-shaped sprayer developed by
Michigan State University engineers to apply pesticides in orchards. The
sprayer uses about 50 percent less chemical per acre and cuts application time
in half. This is because it travels above the trees, moving up and down 5 to 17
feet above ground to accommodate tree height. It can spray two rows at once,
sending low-volume, uniform droplets directly down into the trees.
The sprayer uses only about 25 gallons to cover an acre. Current air-blast
equipment sprays about 50 gallons an acre, one row at a time, shooting straight
into the air and giving uneven coverage. Growers are evaluating the new sprayer
for use on grapes, blueberries, and stone fruits.
Charles C. Reilly, USDA-ARS
Southeastern
Fruit and Tree Nut Research Laboratory, Byron, Georgia; phone (912)
956-6409.
Tackling Trouble on the Grapevine
ARS and Brazilian scientists have teamed
up for a new investigation of the microbe that causes Pierce's disease in
grapevines. The collaboration will reveal the makeup, or sequence, of all of
the genes in the bacterium, Xylella fastidiosa, the organism responsible
for this costly disease. In northern California, Pierce's disease has
chronically attacked vineyards. More recently it has plagued southern
California vineyards, as well.
A half-inch-long insect known as the glassy-winged sharpshooter can harbor
Xylella in its gut, then move the pathogen into plants when it punctures
grapevine stems to feed. Severely infected vines die.
Brazilian scientists have already sequenced the genome of a related Xylella
fastidiosa strain that causes a disease known as citrus variegated
chlorosis. In addition to ARS, sponsors of the new research venture are the
American Vineyard Foundation, the California Department of Food and
Agriculture, and Brazil's State of São Paulo Research Foundation.
Kevin J. Hackett, USDA-ARS
National Program Staff, Beltsville,
Maryland; phone (301) 504-4680.
CO2 Could Aggravate Allergies
Another result of rising atmospheric CO2 may be an increase in
ragweed pollen. Researchers have made pollen counts on ragweed grown in indoor
chambers at various levels of atmospheric CO2. The gas levels ranged
from the turn-of-the-century level of around 280 parts per million (ppm) to
today's 370 ppm and the 600 ppm predicted by the year 2100. Pollen production
went from 5.5 grams to 10 grams to 20 grams per plant as CO2 moved
through these three levels.
Experiments have since moved outside, with researchers checking on ragweed
pollen production in urban, suburban, and rural areas around Baltimore,
Maryland. The project is a collaborative effort of Johns Hopkins University
School of Public Health, Towson University, and Multidata Corporation.
Lewis H. Ziska, USDA-ARS
Climate Stress
Laboratory, Beltsville, Maryland; phone (301) 504-6639.
Improving Aluminum Tolerance in Small Grains
The third most abundant element in the Earth's crust, aluminum is a major
component of soil clay. It causes no problem in neutral or alkaline pH, but in
acidic soils, it damages plant root systems and greatly reduces crop yields.
More than half of the world's 8 billion acres of potential agricultural
land—including about 86 million U.S. acres—have an aluminum problem.
Researchers want to develop crop varieties with increased genetic resistance to
aluminum. They've identified genetic markers for a single gene in barley that
enhances aluminum tolerance. These markers may be used in plant breeding
programs aimed at shuttling aluminum-tolerance genes from tolerant barley
varieties to aluminum-sensitive ones.
Study results also suggest that aluminum tolerance in barley and in wheat, its
close relative, may be owing to the action of different forms of the same gene.
So it may be possible to engineer increased aluminum tolerance in barley by
introducing a wheat gene for aluminum tolerance.
David R. Garvin, USDA-ARS
U.S. Plant, Soil, and
Nutrition Laboratory, Ithaca, New York; phone (607) 255-7308. |
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"Science Update" was published in the
November 2000
issue of Agricultural Research magazine.
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