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United States Department of Agriculture

Agricultural Research Service

Research Project: Discovery, Identification and Risk-Assessment of Biocontrol Agents for Suppression of South American Invasive Weeds and Insects in the U.S.
2012 Annual Report


1a.Objectives (from AD-416):
Research activity at SABCL is aligned with National Program 304, Crop Protection and Quarantine, whose central challenge is the economical and sustainable management of pests in the U.S. minimizing negative consequences to the environment. Accidental introductions of invasive pests into the U.S. from South America have increased as a result of the international trade. Invasive pests cause major ecological and economical losses and often reduce the quality and value of products, increase the cost of production, damage environmental areas and place native species at risk. In addition, they restrict U.S. products from access to valuable foreign markets. Classical biological control offers the possibility for permanent regional suppression of weeds and insect pests that are a threat to U.S. ecosystems. The objectives are: Obj.1) survey South America to discover, collect, and identify biological control agents of target pests; Obj.2) develop rearing techniques and conduct host range and efficacy trials for potential biocontrol agents to identify the most promising candidates; and Obj.3) facilitate exportation of selected candidates to researchers in the U.S. for field release.


1b.Approach (from AD-416):
SABCL research program Project Plan approved by OSQR in 2010 includes target weeds: Brazilian peppertree (Schinus terebinthifolius), Brazilian waterweed (Egeria densa), water primrose (Ludwigia hexapetala), water lettuce (Pistia stratiotes) and waterhyacinth (Eichhornia crassipes). Insect targets are cactus moth (Cactoblastis cactorum), little fire ant (Wasmannia auropunctata), Harrisia cactus mealybug (Hypogeococcus pungens), imported fire ants (Solenopsis invicta and S. richteri) and glassy-winged sharpshooter (Homalodisca vitripennis).

Prior to the collection of their natural enemies, more in depth studies on the biology, ecology, genetics, and/or taxonomy of water primrose, cactus moth and little fire ant are required. These studies are planned as sub-objectives.

Target priorities are set by Congressional mandates, as a result of stakeholder workshops, or by hierarchical decision with input from ARS National Program Leaders (NPLs), stakeholders, SABCL director and ARS scientists. Flexibility in this Project is needed to deal with new pest problems in the U.S., with concurrence of NPLs and ARS laboratories.

SABCL functions as an overseas arm for several U.S.-based biological control programs on invasive pests of South American origin (except glassy-winged sharpshooter), conducting foreign exploration, collection and evaluation of potential biological control agents to be used in the U.S.

Waterhyacinth, Brazilian peppertree, imported fire ants, and glassy-winged sharpshooter were also targets in the previous Project Plan and, except for Brazilian peppertree, Obj.1 and Obj.2 have already been accomplished; current work is limited to collecting and shipping of selected agents (Obj.3). Brazilian waterweed, water primrose, water lettuce, cactus moth, little fire ants and Harrisia cactus mealybug were added by NPLs during the implementation of the previous Project Plan and investigations are in different stages of progress; for the most recently-added targets (cactus moth, little fire ant and Harrisia cactus mealybug), specific approach and procedures for Ob.2 will be determined as soon as natural enemies are discovered, collected and identified.

The general impact of work conducted at SABCL includes conservation of non-renewable resources by self-perpetuation of natural enemies; cost-effective suppression of target pests; decreased use of hazardous pesticides; improved environment quality; protection of natural ecosystems from invasive species, favoring biodiversity; sustainable production systems and land use; higher quality food and fiber; higher protection of human health; enhanced scientific understanding of successful biocontrol programs and integrated pest management.


3.Progress Report:
Brazilian peppertree. Biocontrol agents were surveyed in Argentina and Brazil. Some were found at high densities and several were shipped from Brazil to the quarantine facility at ARS-Ft. Lauderdale, FL. Laboratory host specificity tests are being evaluated.

Brazilian waterweed. An experimental tidal system was constructed to test the suitability of a candidate fly. The experiment consists of transparent polycarbonate tubes with 200 liters of water, hydrosoil at the bottom and ramets planted. A water pump changes the water levels. Flies will be released into the tubes in Spring and damage on the weed will be evaluated. A laboratory colony of the fly was established, clean of parasitoids and pathogens, ready to ship to the U.S.

Water primrose. Morphological and cytological studies of the weed were continued and permitted their reliable identification. Nineteen species of insects were associated to this weed and their field host ranges are being studied.

Water lettuce. A competition, damage, and compatibility test with two natural enemies was evaluated in cages located on a pond covered with the weed in a Natural Reserve. Damage was found to be highly significant representing promising results.

Imported fire ants. An Access and Benefit Sharing agreement, a non funded cooperative agreement (58-6615-119FN), and a Research Project were signed with ARS-CMAVE in Gainesville, FL. These documents are requirements from Argentine regulatory agencies to export genetic resources to the U.S. The evolutionary relationships among 11 species of parasitoid flies revealed that they constitute a monophyletic group. Several putative sibling species have been discovered.

Cactus moth. A large survey to determine field patterns of host use was concluded. The moth attacked hosts proportionally to the availability in all regions. The description of a wasp as new natural enemy was concluded and is being published. Its improved rearing protocol was established to increment colony numbers and the number of females of the offspring. Host range tests revealed that a close-relative moth was attacked as well, but at lower level.

Little fire ant (LFA). Genetic studies were performed to obtain a phylogenetic tree and to construct an unrooted phylogenetic network to identify demographic processes suffered by LFA populations. Thirty three new haplotypes were discovered. New genetic evidence suggested that the presence of this ant in Argentina is the result of a recent range expansion process from Brazil. The thermal tolerance and plasticity of these ants were also studied. Species distribution modeling revealed that the Mediterranean region is not climatically suitable for the establishment of this ant and thus, the population introduced in Israel should not spread into natural habitats in that region. The potential global range expansion included Florida (USA), eastern Australia, New Zealand, New Caledonia, South Africa, Mozambique, Zimbabwe, and Madagascar; Africa is the only region which has not been invaded yet.


4.Accomplishments
1. New legal status for the South American Biological Control Laboratory (SABCL): Creation of the Foundation for the Study of Invasive Species (FUEDEI). The ARS-SABCL was established in Argentina in 1962 and as it functioned as a part of the U.S. Embassy in Buenos Aires, it never needed a specific, different legal status. However, in 2011 the Argentine Government mandated the creation of a new entity to replace SABCL, separate from the U.S. Embassy and with its own legal status to operate in Argentina. SABCL was then transformed into a non-profit independent entity: the Foundation for the Study of Invasive Species (legal name in Spanish: Fundacion para el Estudio de Especies Invasivas, (FUEDEI). FUEDEI was officially created on March 16, 2012 and legally registered as a foundation on April 16, 2012. FUEDEI is now recognized as a research institution and is authorized to operate in Argentina. The transition SABCL-FUEDEI will terminate on September 30, 2012. This accomplishment will greatly facilitate obtaining the export permits for the natural enemies selected for biocontrol.

2. Discovery of 33 new genetic forms (haplotypes) of the little fire ant. During the field explorations and studies on the target pests and their natural enemies, a number of organisms are usually found and collected for testing. Prior to the testing process, the accurate taxonomic identification of the natural enemies by classical procedures or by more sophisticated molecular methods is a key aspect for the success of the projects. During the extensive field explorations in FY 2012, ARS-SABCL scientists in Argentina co-discovered 33 new haplotypes of the little fire ant in its southern distribution limit. The great genetic variability in the southern limit suggests that those populations have not been introduced anthropically. Instead, they might reflect a recent (in evolutionary times) natural expansion from northern populations, mainly from Brazil. The demographic expansion associated with cold tolerance seems to be associated with clonality since all the populations of the network analyzed up to now were clonal. These findings will help to better understand their invasion process and, consequently, the safest and most efficient control approach.

3. High host specificity of four agents for biocontrol. As stated in 4.2, during the field explorations, a number of organisms are usually found and collected for testing. Host specificity of the natural enemies is a key factor to consider while selecting agents for biocontrol. This way, non-target effects are avoided. During FY 2012, ARS-SABCL scientists in Argentina confirmed high specificity of one fly for alligator weed, one beetle for lippia, one rust for water pennywort, and one wasp for the cactus moth. These agents will be considered for exportation to quarantine facilities and eventual field release to mitigate the damage of those invasive pests.


Review Publications
Briano, J., Calcaterra, L., Varone, L. 2012. Fire ants (Solenopsis spp.)and their natural enemies in southern South America. Psyche. DOI: 10.1155/2012/198084.

Mc Kay, F., Oleiro, M.I., Diniz Vitorino, M., Wheeler, G.S. 2012. The leafmining Leurocephala schinusae (Lepidoptera Gracillariidae): Not suitable for the biological control of Schinus terebinthifolius (Sapindales Anacardiaceae)in continental USA. Biocontrol Science and Technology. 22(4):477-489. DOI: 10.1080/09583157.2012.664618.

Logarzo, G.A., Zamar, M., Richman, D., Bruzone, O. 2012. Structure and composition of a thrips community in the Chihuahua Desert, New Mexico, U.S.. Florida Entomologist. 95(1):35-42.

Julien, M., Sosa, A.J., Traversa, G., Van Klinken, R. 2012. Phyla canescens (Kunth) Greene-lippia. Book Chapter. In:Julien, M.; McFadyen, R.; Cullen,J. editors. Biological Control of Weeds in Australia. Australia: CSIRO Publishing. p.463-471.

Julien, M., Sosa, A., Chan, R., Schooler, S., Traversa, G. 2012. Alternathera philoxeroides (Martius) Grisebach - alligator weed. Book Chapter. In: Julien, M.; McFadyen, R.; Cullen, J., editors. Biological Control of Weeds in Australia.Australia: CSIRO Publishing. p.43-51.

De Leon, J.H., Setamou, M., Gastaminza, G., Buenahora, J., Caceres, S., Yamamoto, P., Bouvet, J.P., Logarzo, G. 2011. Two separate introductions of Asian citrus psyllid populations found in the American continents. Annals of the Entomological Society of America. 104(6):1392-1398.

Briano, J., Varone, L., Logarzo, G., Villamil, C. 2012. Extended geographical distribution and host range of the cactus moth Cactoblastis cactorum (Lepidoptera Pyralidae)in Argentina. Florida Entomologist. 95(1):233-237.

Calcaterra, L., Coulin, C., Briano, J., Follett, P.A. 2012. Acute exposure to low dose radiation disrupts reproduction and shortens survival of Wasmannia auropunctata (Hymenoptera Formicidae)queens. Journal of Economic Entomology. 105(3):817-822.

Cabrera Walsh, G. 2012. Chrysomelids American diabroticines Hosts and natural enemies. Biology-feasibility for control of pest species (Crisomelidos Diabroticinos americanos Hospederos y enemigos naturales Biologia y factibili manejo especies plagas. Chrysomelids American Diabroticines: Hosts and natural enemies. Spain:Editorial Academica Espanola. p.1-143.

Cabrera Walsh, G., Dalto, Y., Mattioli, F., Carruthers, R.I., Anderson, L.W. 2013. Biology and ecology of Brazilian elodea (Egeria densa) and its specific herbivore Hydrellia sp in Argentina. Biocontrol. DOI 10.1007/s10526-012-9475-x.

Cabrera Walsh, G., Briano, J., Briano, A. 2012. El control biologico de plagas(Biological control of pests). Ciencia Hoy. 22(128):57-64.

Cabrera, N., Cabrera Walsh, G. 2010. Diabrotica collicola (Coleoptera: Chrysomelidae)a new species of leaf beetle from Argentina Discussion and key to some similar species of the Diabrotica virgifera group. Zootaxa. 2683:45-55.

Brooks, C.P., Ervin, G.N., Varone, L., Logarzo, G. 2012. Native ecotypic variation and the role of host identity in the spread of an invasive herbivore Cactoblastis cactorum (Berg). Ecology. 93(2):402-410.

Last Modified: 8/27/2014
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