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Oi D.H.,U.S. Department of Agriculture | Valles S.M.,U.S. Department of Agriculture | Briano J.A.,South American Biological Control Laboratory
Biological Control | Year: 2010

The host specificity of Vairimorpha invictae, a microsporidian pathogen of fire ants in South America, was assessed in the laboratory. Species evaluated included the tropical fire ant, Solenopsis geminata, the southern fire ant, Solenopsis xyloni, and the Argentine ant, Linepithema humile. The two fire ant species are native to North America. The Argentine ant is a widespread, exotic species that co-occurs with the native North American fire ants as well as with the red imported fire ant, Solenopsis invicta, and the black imported fire ant, Solenopsis richteri, in the US. Inoculations of V. invictae-infected S. invicta brood to laboratory colonies did not result in any infections of S. geminata, S. xyloni, or L. humile, while 60% of the S. invicta colonies developed infections. V. invictae was not detected in smaller groups of S. geminata and S. xyloni larvae that were tended by V. invictae-infected adult, S. invicta workers, but was detected in 40% of the S. invicta larval groups tended by infected workers. This was the first report of V. invictae transmission to larvae by infected adult worker ants. Exposure to V. invictae by contact with infected brood and workers partially emulated possible field interactions between infected and uninfected ant species. These results are congruent with previous field surveys which indicate that the host range of V. invictae is limited to fire ants of the Solenopsis saevissima species group.

Porter S.D.,U.S. Department of Agriculture | Graham L.C.,Auburn University | Johnson S.J.,Louisiana State University | Thead L.G.,U.S. Department of Agriculture | Briano J.A.,South American Biological Control Laboratory
Florida Entomologist | Year: 2011

The large fire ant decapitating fly, Pseudacteon litoralis Borgmeier, from northeastern Argentina was successfully released as a self-sustaining biocontrol agent of imported fire ants in south central Alabama in 2005. Five years later, this fly is firmly established at the original release site and has expanded outward at least 18 km. Nevertheless, populations remain very low considering P. litoralis is one of the most abundant fire ant decapitating flies in large areas of its range in South America. The reasons for low densities and why we were only able to establish this fly at 1 of 9 release sites in 4 states (2003-2006) are unknown, but problems with host-matching, release procedures, weather conditions, and competition with previously released decapitating flies are discussed as possible factors.

De Leon J.H.,U.S. Department of Agriculture | Setamou M.,Texas A&M University-Kingsville | Gastaminza G.A.,Seccion Zoologia Agricola | Buenahora J.,Instituto Nacional Of Investigacion Agropecuaria Inia | And 4 more authors.
Annals of the Entomological Society of America | Year: 2011

A phylogeographic analysis inferred from the partial mitochondrial cytochrome oxidase subunit I gene (433 bp) was performed with 22 populations of Diaphorina citri Kuwayama collected in the Americas and one in the Pacific. Eight populations from four countries in South America, 14 from four countries in North America, and one from Hawaii were analyzed. Twenty-three haplotypes (hp) were identified and they fell into two groups: hp1-8 were identified in South America (group 1) and hp9-23 were identified in North America and Hawaii (group 2). Hp1 and nine were present in the highest frequencies within each population and within their group, 81 and 85% for group 1 and group 2, respectively. A diagnostic nucleotide at position 48 was identified that allowed for the discrimination of the two groups; in addition, no haplotypes were shared between the two groups. An analysis of molecular variance uncovered significant genetic structure (Φ CT = 0.733; P < 0.001) between the two groups of the Americas. Two haplotype networks (ParsimonySplits and Statistical Parsimony) discriminated the two groups and both networks identified hp1 and nine as the predicted ancestral or founding haplotypes within their respective group. The data suggest that two separate introductions or founding events of D. citri occurred in the Americas, one in South America and one in North America. Furthermore, North America and Hawaii appear to share a similar source of invasion. These data may be important to the development of biological control programs against D. citri in the Americas.

Porter S.D.,U.S. Department of Agriculture | Calcaterra L.A.,South American Biological Control Laboratory
Biological Control | Year: 2013

Self-sustaining classical biological control agents offer hope for permanent wide-area control of imported Solenopsis fire ants in the United States because escape from abundant natural enemies left behind in Argentina is a likely reason for unusually high fire ant densities in the United States. The fire ant decapitating fly Pseudacteon obtusus Borgmeier (Diptera: Phoridae) was released as a biocontrol agent of the red imported fire ant (Solenopsis invicta Buren) in Gainesville, FL because it is a common parasitoid of this ant in Argentina and because it has a higher propensity of attacking fire ants along foraging trails than the two Pseudacteon species previously released. Field surveys of a rapidly expanding P. obtusus population (8-12. km/yr) proved that this fly was capable of thriving and successfully competing with the much more abundant Pseudacteon curvatus Borgmeier. However, Pseudacteon tricuspis Borgmeier, the first decapitating fly released, was effectively excluded from most sample sites when faced with competition from both P. curvatus and the similar-sized P. obtusus. Despite clear evidence for competitive exclusion, P. tricuspis abundance at sample sites was positively correlated with the abundance of its two competitors-probably because of moderate to strong covariability in the suitability of sample sites for all three congeners. The addition of P. curvatus, the second parasitoid released, increased total parasitism pressure on fire ant populations by about 10-fold. The addition of P. obtusus, the third species, did not measurably improve total guild parasitism rates on imported fire ants in North Central Florida (as assessed by roadside trap counts), but the performance of this species will likely vary with habitat, region, and climate. © 2012.

Oleiro M.,South American Biological Control Laboratory | Kay F.M.,South American Biological Control Laboratory | Wheeler G.S.,U.S. Department of Agriculture
Environmental Entomology | Year: 2011

During surveys for natural enemies that could be used as classical biological control agents of Schinus terebinthifolius Raddi (Brazilian pepper), the caterpillar, Tecmessa elegans Schaus (Lepidoptera: Notodontidae), was recorded feeding on the leaves of the shrub in South America. The biology and larval and adult host range of this species were examined to determine the insect's suitability for biological control of this invasive weed in North America and Hawaii. Biological observations indicate that the larvae have five instars. When disturbed, the late instar larvae emit formic acid from a prothoracic gland that may protect larvae from generalist predators. Larval host range tests conducted both in South and North America indicated that this species feeds and completes development primarily on members of the Anacardiaceae within the tribe Rhoeae. Oviposition tests indicated that when given a choice in large cages the adults will select the target weed over Pistacia spp. However, considering the many valued plant species in its host range, especially several North American natives, this species will not be considered further for biological control of S. terebinthifolius in North America. © 2011 Entomological Society of America.

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