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A new wood-boring wasp species, discovered in coniferous forests in
Chile, could threaten U.S. forests. Wood-boring wasps already in this
country cause millions of dollars of damage each year. They can reduce
the quality of lumber and cause concern to building owners when adult
insects emerge after wood is used in construction. ARS scientists
identified the new wasp, Derecyrta beechei, n. sp., in the family
Xiphydriidae. That identification is critical, because the species
possess characteristics similar to two other known types of wood-boring
wasps. Wood borers can be transported in commercial shipping, so
preventing their introduction into the United States and other countries
is important. If these pests are encountered at ports of entry, specific
identification could save action agencies like USDA's Animal and Plant
Health Inspection Service time and money in detecting them and disposing
of infested materials.
Systematic
Entomology Laboratory, Washington, DC
David R. Smith, (202) 382-1783
Three new "half-runner" snap beans have been developed to resist the
rust fungus, Uromyces appendiculatus. That should please
gardeners and commercial growers, especially in the Appalachian region of
Tennessee, North Carolina and West Virginia. Half-runnerswhose vines run
along the groundare popular in the region. But available half-runner
varieties are extremely vulnerable to attack by the fungus. Under cool,
moist conditions, it can erase 50 to 80 percent of the potential yield.
To combat the fungus, ARS and University of Tennessee scientists released
the seed of three new bean germplasm lines to plant breeders. BelTenn
Rust-Resistant 1, 2 and 3 ward off all 66 known races of U.
appendiculatus. BelTenn vines grow one to two feet long and produce
tasty, large, white beans with edible pods. To develop the new lines,
scientists made several crosses of a rust-resistant Guatemalan bean,
several experimental lines and a commercial variety, Mountaineer White
Half-Runner. They then verified the resistance trait in progeny from each
cross.
Molecular Plant
Pathology Laboratory, Beltsville, MD
J. Rennie Stavely, (301) 504-6600
An altered strain of bacteria may defend snap beans against brown spot
disease. An ARS researcher developed a non-disease-causing strain of
Pseudomonas pv syringae, the bacteria that normally causes brown
spots in beans. In field studies conducted with University of Wisconsin
scientists in 1991 and 1993, the altered bacteria sprayed on beans
suppressed numbers of its disease-causing parent by as much as 98 percent.
In a wet season growers in Wisconsin may lose about $1 million in
unmarketable beans because of brown spots. If this bacterium can be
developed into a product to control brown spot, these growers might
benefit. Other states that produce sizeable green bean harvests include
Illinois, Michigan and Oregon.
Plant Disease Resistance, Madison, WI
Christen D. Upper/D. Kyle Willis, (608) 263-2092
One cherry grower in northern California who followed recommendations
for controlling buckskin disease confined infection to an average three
percent in his orchard during a six-year period. Another who ignored
his buckskin problem had more than 60 percent of his trees infected. The
disease is often fatal to cherry trees, wiping out entire orchards in two
or three years. But ARS researchers have proven to growers that buckskin
can be kept in check by following a series of guidelines that thwart its
spread. Recommendations include prompt removal of infected trees and tree
stumps, monitoring for leafhoppers that carry disease microorganisms, and
careful insecticide applications. Scientists are now working on more
sensitive tests to detect the disease-causing organism, a mycoplasmalike
microorganism. The tests would more readily identify which plants are
serving as disease reservoirs. Buckskin was first noted in California in
1931, then was quickly identified in eastern U.S. orchards and in
Washington state.
Crops Pathology and Genetics Research Unit, Davis, CA
Jerry K. Uyemoto, (916) 752-0309
Hairy nightshade, a common weed in potato-growing areas of Washington
and New York, is harboring fungicide-resistant strains of the fungus that
causes potato late blight. Phytophthora infestans
unfortunately is now resistant to the most widely used chemicals. ARS
scientists say the weed appears to be an alternate host for this fungus
during periods when there are no potatoes or tomatoes. Growers must use
culling, good sanitation practices and other non-chemical measures to
control late blight, the disease that caused the 1845 Irish potato famine.
Up to 20 percent of the U.S. potato crop succumbed to potato late blight
during the past three years, with losses totaling $200 million in
1994.
Vegetable
Laboratory, Beltsville, MD
Kenneth L. Deahl, (301) 504-5216
Last updated: October 29, 1996
Return to: Quarterly Report
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