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A newly released breeding line of citrus resists the citrus tristeza
virus (CTV). The new line, developed by an ARS plant breeder and dubbed US
119, is being used to breed citrus varieties that fight off the virus.
CTV-resistant citrus is more important than ever, because in November
1995, the brown citrus aphid was found in Fort Lauderdale, FL. This aphid
carries severe strains of CTV that are not present in Florida, and the
pest transmits the virus when it feeds on citrus trees. Scientists and
citrus industry leaders have worked for several years to prepare for the
potential arrival of this pest in Florida citrus groves. It has been
estimated that the aphid could cost the citrus industry more than $1
billion over the next few years.
Horticultural
Research Laboratory, Orlando, FL
Herb C. Barrett, (407) 897-7300
Abamectin, a natural ingredient produced by a common soil
microorganism, knocks out the pesky Caribbean fruit fly. Produced by
the fungus Streptomyces avermitilis, this biological bait additive
could be a possible alternative to malathion, the insecticide growers now
use against the carib fly. Currently the only alternative to malathion is
methyl bromide, which is being phased out in 2001. Abamectin, which
breaks down rapidly, works by paralyzing the fly's nervous system, leading
to death. In lab tests, the abamectin-laced bait was 100 percent
effective at 50 parts per million, only 0.03 percent of the amount of
malathion needed to do the same job. Another form of abamectin is
registered for use against Florida's citrus rust mite. ARS scientists are
applying for a patent and are looking for ways to commercialize the
product. The new bait can be applied with the same equipment now used for
malathion. Fresh citrus shipped to Japan, Thailand, California, Texas,
Bermuda and Hawaii must be certified free of the Caribbean fruit fly.
Subtropical
Horticulture Research Laboratory, Miami, FL
Michael K. Hennessey/Jimmie R. King, (305) 254-3627
A light-activated dye kills Mediterranean and oriental fruit flies, ARS
scientists have shown for the first time. Earlier work, at
Mississippi State University and elsewhere, proved that photoactive
colorants called xanthenes can zap other insect pests. Now, ARS
researchers and PhotoDye International, Inc., are seeking a patent to use
xanthenes such as FDA-approved D&C red number 28 to kill the two fruit
flies. The dye could be mixed with a bait and another dye to make the
meal even more lethal. In the past five years, U.S. taxpayers have spent
more than $100 million to fight Medflies and oriental fruit flies in
mainland states such as California. The dye goes into action after the
flies eat it and then spend time in the sun. Scientists think that the
compounds, when light-activated, release a form of oxygen that is toxic to
these insects. (PATENT APPLICATIONS 08/353,726 and 08/414,402)
Tropical Fruit and Vegetable Research Laboratory, Hilo, HI
Nicanor J. Liquido, (808) 959-4344
The Mediterranean fruit fly's habit of approaching an alluring scent
indirectly, instead of straight-on, is key to a new trap. Hung from
trees, the device has three removable panels spaced approximately an inch
apart. Medflies are attracted by the slow-release lure impregnated in the
middle panel, a six- by-six-inch plastic square. Heading to or from the
scent's source, the flies can get nabbed by the sticky coating on the two
outer panels that are made of nine-by-5.5-inch paperboard. When medflies
invade states like California or Florida, the new trap could be used to
find their invasion boundaries. Then agricultural agencies can map a
counterattack. Today's sticky traps consist of a single panel with medfly
lure mixed into the coating. These traps may run out of lure in two
weeks. The new traps, with a controlled-release lure, last about two
months or more, according to preliminary outdoor tests. ARS and Farma
Tech International, Fresno, CA, invented the trap. (PATENT APPLICATION
08/248,365)
Tropical Fruit and Vegetable Research Laboratory, Hilo, HI
Roy T. Cunningham, (808) 959-4300
To keep corn free of a toxin made by a fungus, farmers might someday
plant seeds coated with a harmless bacterium. ARS researchers
discovered that the fungus and bacterium are endophytes--natural
inhabitants of corn plants rather than "outsiders." If further tests
succeed, Enterobacter cloacae bacteria applied to corn seed would
enter and spread through the plant after it germinates. This is how the
bacterium gave corn plants a built-in defense against the fungus,
Fusarium moniliforme, in greenhouse tests and small outdoor trials
by ARS and University of Georgia scientists. F. moniliforme and
related fungi infect many grain, fruit and vegetable crops. The fungi
also make fumonisins--toxins blamed for contaminating corn-based feeds and
foods. Previously, scientists thought the fungus was always a pathogen.
But ARS researchers found that it is not always a pathogen. They found it
inside nearly all commercial corn cultivars they examined. In a seed
sample from Italy, however, they found only endophytic bacteria--no fungi.
Scientists don't yet know if the E. cloacae bacteria actually
attack fungal cells, or simply outcompete them for living space inside the
corn plant. The scientists plan larger outdoor tests next summer.
Toxicology
and Mycotoxin Research Unit, Athens, GA
Charles Bacon, (706) 546-3158
Last updated: October 28, 1996
Return to: Quarterly Report
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