New Lure May Help Conserve
Helpful, Sterile Medflies
By Tara Weaver
July 31, 1997
GAINESVILLE, Fla., July 31--The newest Mediterranean fruit
fly lure being field-tested in the Tampa, Fla., area may have an additional
advantage over conventional lures in medfly traps, said the
U.S. Department of Agriculture scientists
who developed it.
"Ideally, we only want to trap egg-laying female medflies, and our
new lure does this better than other lures tested," said chemist
Bob Heath with USDA's
Agricultural Research Service in
Gainesville, Fla. "The new lure also could prove less appealing to sterile male
That would help the Florida Department of Agriculture, which began
releasing millions of sterile medflies July 25. The sterile flies' job is to
mate with any wild females that survived the recent malathion sprays. Since
none of the offspring of these matings survive to maturity, the sterile-release
tactic disrupts the pests' reproductive cycle, Heath noted.
He said traps using the new ARS lure could be placed in sterile-release
areas within a couple of weeks. "Our newest lure is relatively unappealing
to the steriles because it smells like protein. Sterile male flies, unlike
fertile females, don't need protein," Heath said. He and ARS entomologist
Nancy Epsky co-developed
the new lure at ARS' Center for Medical,
Agricultural, and Veterinary Entomology in Gainesville, Fla.
"We placed 50 traps with our attractant in the Tampa Bay area for
a demonstration project, to test it during an actual medfly outbreak," Heath
said. "We caught about 150 medflies in six days. The several hundred other
traps in the Tampa area caught 200 medflies in three weeks. Our traps accounted
for 80 percent of all the females caught in all the traps."
A potent synthetic attractant for female medflies has been a major
hurdle in designing medfly lures. But "in our traps, 50 to 90 percent of the
medflies captured are females," Heath said.
That's because the new lure mimics a high protein source, said
Epsky. "The females are attracted because they are developing eggs and have
very high food needs compared to the males," she said.
The newest lure has three components--ammonium acetate, putrescine
and trimethylamine. The researchers' previous lure had only the first two. The
trimethylamine greatly improves female capture, Epsky said.
All three chemicals are emitted from the medfly's natural food
sites such as citrus trees, Heath noted.
For the new three-component lure, the Tampa-area test is the
largest to date in the United States, Heath said. "California is testing some
traps baited with the three-component attractant to detect medflies. There has
been no widespread use of our lures in the United States. But Portugal, Spain,
Greece, Israel and Guatemala have used them in detection and eradication
programs for several years."
California, Texas and Florida use large numbers of
trimedlure-baited Jackson traps to detect male flies and protein-baited McPhail
traps for male and female flies. Both trap systems have problems.
The glass McPhail traps attract both male and females, but are
fragile, cumbersome and difficult to service. Each week, they have to be
removed and cleaned, and the baits have to be replaced. They also capture many
Trimedlure, the main lure in Jackson traps, is very attractive to
male medflies. But it only weakly attracts females, which are crucial targets
because their eggs represent the makings of a wider medfly infestation.
Trimedlure baited traps also capture large numbers of sterile male flies.
"Our synthetic food lure captures both females and males, but
attracts fewer non-target insects than the protein-baited traps," Heath said.
The researchers' newest attractant is used in a cylindrical
plastic trap that protects it from the environment. Each of the three lures
comes in its own sealed package and can be placed in a trap without removing it
from a site. The trap can be used with or without water, and the lures last 6
to 8 weeks.
Scientific contacts: Robert R. Heath and Nancy Epsky, Chemistry
Research Unit, Center for Medical, Agricultural, and Veterinary Entomology,
Agricultural Research Service, USDA, Gainesville, Fla. 14565. Heath: phone
352-374-5735, fax 352-374-5859, email@example.com.
Epsky: phone 352-374-5816, fax 352-374-5859, firstname.lastname@example.org