Establishment of the Phorid Fly, Pseudacteon curvatus,

1
Establishment of the Phorid Fly, Pseudacteon
curvatus, in Alabama for Biological Control of
Imported Fire Ants L. C. Graham1, V. E.
Bertagnolli1, S. D. Porter2, H. D. Dorough3, and
A. T. Kelley4 1Department of Entomology and Plant
Pathology, Auburn University, Auburn, Alabama
36849-5413 2USDA-ARS Center for Medical and
Veterinary Entomology, Gainesville, Florida
32604 3Auburn University, Alabama Cooperative
Extension System, Talladega, Alabama
35160 4Department of Entomology and Plant
Pathology, Mississippi State University,
Starkville, Mississippi 39762-9775
Photo courtesy of S. Porter
Photo courtesy of S. Porter
Introduction
Methods and Materials
Fire ants were collected from a farm in
Talladega County and were shipped to S. Porter in
Gainesville, FL. The collected ants were
identified as hybrids of S. invicta and S.
richteri by their color and cuticular hydrocarbon
patterns. Once confirmation of a hybrid
population was received, mounds at the site were
individually marked with numbered flags.
Approximately five grams of workers were
collected from a mound and placed into a plastic
container labeled to correspond to the mound
number. Workers were collected from between five
and eight mounds on a single date, beginning May
3, 2000. The plastic containers with the workers
inside were placed into a cooler with an ice pack
and shipped overnight to S. Porter. The workers
were exposed to a laboratory colony of P.
curvatus for 2-3 days. The workers were then
repackaged and shipped overnight back to our lab
or to H. Dorough in Talladega County. Exposed
workers were returned to the field within 24
hours of receipt and were placed into the mound
from which they were originally removed. This
process was repeated a total of six times. The
last release of workers was May 31. Workers were
collected from and returned to a total of 38
mounds.
When fire ants were introduced into Alabama in
the early 1900's, almost all of their natural
enemies were left behind in South America
(Jouvenaz, 1990). As a result, fire ant
densities are much higher in Alabama than they
are in South America (Porter et al., 1997). Two
species of imported fire ant occur in Alabama.
The red imported fire ant, Solenopsis invicta, is
located primarily in the southern portion of the
state. The black imported fire ant, Solenopsis
richteri, is now only found in a small population
located in northwest Alabama and northeast
Mississippi. A hybrid of the two species
populates the northern part of Alabama. One
group of natural enemies that have shown some
promise in the battle against fire ants are
phorid flies in the genus Pseudacteon (Porter,
2000). These flies have the unusual habit of
decapitating fire ant workers. Pseudacteon
tricuspis was released into S. invicta
populations in southern Alabama and has been
established since 1999. Pseudacteon curvatus was
released into the hybrid fire ant population
located in Talladega County in 2000.
Pseudacteon spp. release sites in Alabama
Results and Discussion
The search for a resident population of P.
curvatus was initiated on June 16, 2000. The
first siting of P. curvatus occurred on Aug. 10.
Three flies were captured on Aug. 14 and were
positively identified as P. curvatus. Flies were
observed at the site again on Aug. 28 and Sep. 14
and 26. In 2001, flies were found in May and
July. On Aug 16, several areas around the
release site were sampled. No flies were found
to the south of the release site. However the
phorids were found in mounds approximately 1.1
kilometers north of the release site. This is
the first successful establishment of Pseudacteon
curvatus in the United States.
P. curvatus, Talladega Co., 2000
x
1.1 K
P. tricuspis, Macon Co., 1999
x
Photo courtesy of S. Porter
x
18 K
P. tricuspis, Houston Co., 2000
P. curvatus ovipositor
x
P. tricuspis, Lowndes Co., 2001
References
Jouvenaz, D. P. 1990. Approaches to biological
control of fire ants in the United States. In
Applied Myrmecology World Perspective (R.
K. Vander Meer, K. Jaffe, and A. Cedeno, Eds.),
pp. 620-27. Westview Press, Boulder CO. Porter,
S. D., Williams, D. F., Patterson, R. S., and
Fowler, H. G. 1997. Intercontinental differences
in the abundance of Solenopsis fire ants
(Hymenoptera Formicidae) Escape from natural
enemies? Environ. Entomol. 26 373-84. Porter, S.
D., 2000. Host specificity and risk assessment of
releasing the decapitating fly Pseudacteon
curvatus as a classical biocontrol agent for
imported fire ants. Biol. Control 19 35-47.
Circles indicate movement in kilometers from
release site.