Weeds

Waterhyacinth, Eichhornia crassipes
Alligator weed, Alternanthera philoxeroides
Lippia, Phyla canescens
Mesquite, Prosopis spp.
Fanwort, Cabomba caroliniana
Brazilian pepper, Schinus terebinthifolius
Brazilian water weed, Egeria densa
Water primrose, Ludwigia hexapetala
Balloon vine, Pompom weed, Barbados gooseberry, Cat´s claw, Cardiospermum grandiflorum, Campuloclinium macrocephalum, Pereskia aculeata, Macfaydena ungis-cati

Insects

Imported Fire Ants, Solenopsis invicta & S. richteri
Glassy Winged Sharpshooter, Homalodisca vitripennis
Corn Rootworms, Diabrotica spp.
Cactus moth, Cactoblastis cactorum

    Waterhyacinth

Eichhornia crassipes 

M. Cristina Hernández
Alejandro Sosa
Guillermo Cabrera
Gerardo Elsesser

Cooperators: Ted Center, Phil Tipping, USDA-ARS-Invasive Plants Research Laboratory, Ft. Lauderdale, FL, USA. and Martin Hill, Rhodes University, South Africa
IPRL, Fort Lauderdale, Florida
PPRI, South Africa

Waterhyacinth is considered the world’s worst aquatic weed in tropical and subtropical water bodies.  It was introduced into the U.S.A. and many other countries in the late 19th and early 20th centuries (Julien, 2001) In more recent years it continues to spread throughout Africa, and even in Latin American countries, where it is considered to be native, but outside the normal range and without the presence of its natural enemies (DeLoach and Cordo, 1975; Labrada 1996). It spreads at a dramatic rate, particularly under the combination of eutrophication of water bodies and absence of its natural enemies. In the U.S.A. it occurs in the southeastern states, California and Hawaii. The ecological and economic damages that Waterhyacinth still causes in the U.S.A., has recently been summarized by Center et al. (2002).

Although biocontrol has proved to be the most effective method to provide long-term results in controlling E. crassipes, additional agents are needed. Also, weed management including biocontrol, herbicide applications and physical removal, will be necessary to control the plant in all the habitats (Julien, 2000). Some of the Waterhyacinth natural enemies with potential to be used as biocontrol agents, are currently being studied at the SABCL. Tests conducted with the mining fly Thrypticus truncatus and the delphacid plant hopper Megamelus scutellaris, showed high specificity on WH of both candidates. Megamelus scutellaris was shipped to quarantine at ARS-IPRL in Ft. Lauderdale for further studies in 2006 and petition for field release was recently requested.

A new candidate is currently under study: Taosa sp. (Hemiptera; Dictyopharidae). This plant hopper was found in many exploratory trips in South America. The specimens, collected by SABCL personnel, probably include three undescribed species, some of which may be WH specialist. The research includes taxonomy, biology and specificity. In 2007, an important detrimental effect of T. inexacta was confirmed. Both Thrypticus truncatus and Taosa sp. were shipped to quarantine at IPRL in early 2008.

Annual Report 2007 
       Annual Report 2008

FOR MORE INFORMATION CONTACT CRISTINA HERNANDEZ crisher@speedy.com.ar

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    Alligator weed

Alternanthera philoxeroides 

Alejandro Sosa
Marta Telesnicki

Cooperator: Mic Julien, CSIRO European Laboratory, Montferrier sur Lez, France
CSIRO Entomology

This project has been conducted by SABCL since October 2001 after an agreement between the USDA-ARS and CSIRO (Australia). The CSIRO initiated this collaborative research project in Argentina to search for new biological agents, update the list of natural enemies known and to determine the native range of the weed.

Alligator weed, Alternanthera philoxeroides (Mart.) Griseb, is an herbaceous amphibious weed of the Amaranthaceae, native to southern South America. In Argentina, alligator weed is distributed along the catchments of the Paraná and Uruguay rivers in northern Argentina, and in the catchments of the San Borombón and Salado rivers in the centre of Buenos Aires province. The plant was introduced into many countries becoming in a serious aquatic and terrestrial weed.

This weed drew the attention of biological control specialists in USA in the 1960´s and surveys were carried out at that time in its natural range (South America) and a list of its natural enemies was made. Based on this list, three biological agents that were considered the most important suppressants of alligator weed, were  released in the USA for control of the weed.  They were, the flea beetle Agasicles hygrophila Selman and Vogt, the moth Arcola malloi (Pastrana) and the thrips Aminothrips andensonii O´Neill (Spencer and Coulson 1976). The flea beetle and the moths were subsequently released in Australia and controlled the weed in warm temperate aquatic habitats (Julien and Griffiths 1999). However, terrestrial growth of the weed and aquatic growth in cooler regions of Australia continue to cause serious concern (Julien and Bourne 1988), so new agents are needed to control the weed in such circumstances.

New agents have been found: chrysomelid foliage feeding beetles (Systena and Phenrica sp.), a tiny fly that causes tip galls (Clinodiplosis alternantherae), another fly that galls the nodes (Ophiomyia marellii), a stem mining fly (possibly Ophiomyia buscki) and two flies that mine the leaves (Ophiomyia alternantherae and an unidentified one). Pathogens found include one known to have a wide host range (Nymbia alternantherae), and another that causes a corky deformation of the stem and leaf surfaces and may be a new species (Sphaceloma sp.?). Clinodiplosis alternantherae was recently shipped to quarantine in Brisbane, Australia for further research and eventual field release. In 2007, genetic effects of the plant were discovered on the life cycle of Agasicles hygrophila.

Annual Report 2007 
Annual Report 2008

FOR MORE INFORMATION CONTACT ALEJANDRO SOSA alejsosa@speedy.com.ar

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    Lippia

Phyla canescens 

Alejandro Sosa
Marta Telesnicki

Cooperator: Mic Julien, CSIRO European Laboratory, Montferrier sur Lez, France
CSIRO Entomology

Lippia, Phyla canescens (Kunth) Greene is a member of the family Verbenaceae. This fast-growing, mat-forming plant is native to South America and was introduced into Australia during the second half of the nineteenth century, probably as an ornamental plant. Its spreading nature and deep rooting system are associated with stream bank and soil erosion, structural damage to roads and high control costs.

Several strategies have been proposed for its control. An agreement with CSIRO (Australia) has been signed and SABCL initiated studies of the plant to determine (1) the centre of origin, (2) the distribution range and (3) the potential biological control agents. Both insects and pathogens are being considered. Pathogens are being studied with the cooperation of Guadalupe Traversa, PhD student at the Universidad Nacional del Sur, Bahía Blanca, Argentina.

So far, 21 agents have been found: four beetles (Chrysomelidae), a leaf mining fly (Agromyzidae?), two thrips (Thysanoptera), four species of Lepidoptera (two micro moths and two hairy caterpillars), eriophyid mites, unidentified stem gallers, four leafhoppers (Cicadellidae), two Cercopidae and recently (May 2007) a weevil. Longitarsus spp. were found throughout the ranges of both plants, only as adults feeding on leaves. Larvae are possibly root feeders as recorded on other Longitarsus sp. feeding on verbenaceous plants (Simelane 2005) but lab rearing has not yet been successful.

The flea-beetle Kuschelina bergi Harold, was found on litter or the ground amongst prostrate stems. In the lab it has five larval stages and takes about two months to complete its cycle. Pupation occurs in the substrate and takes about two weeks. Further studies including host range tests are planned.

Pathogens.  Some fungi associated with Phyla spp. are secondary invaders (Nigrospora, Sordaria, Podospora, etc), others are clearly pathogenic (Puccinia cf. lantanae, Cercospora cf. lippiae, Colletotrichum spp.) and some others have unknown pathobiology (Fusarium sp., Bipolaris sp., Alternaria sp., Phoma sp., Phomopsis sp.). Cercospora cf. lippiae was the most widespread among the parasitic species and causes a necrotic leaf spot which might inflict important damage to the host. There are at least three Colletotrichum spp. involved in leaf spot symptoms; one of them might be a new species. The microcyclic rust (Puccinia cf. lantanae) should be one of the candidates to be studied, but unfortunately the host seems to be Phyla reptans rather than P. canescens, although the original record (Spegazzini 1909) refers to the latter species.

Annual Report 2007 
       Annual Report 2008

FOR MORE INFORMATION CONTACT ALEJANDRO SOSA alejsosa@speedy.com.ar

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Prosopis spp.

Fernando Mc Kay
Marina Oleiro

Cooperator: Arne Witt, Agricultural Research Council, Plant Protection Research Institute, Pretoria, South Africa.
PPRI, South Africa

This project was conducted at the SABCL after an agreement between the USDA-ARS and the Plant Protection Research Institute (PPRI), South Africa, signed in August 2002. The objective was to find biological control agents with the ability to reduce the negative impact caused by invasive mesquite species in arid and semi-arid lands in South Africa. Five mesquite species (Prosopis spp., Leguminosae) were introduced in South Africa during the XIX century, and their propagation was encouraged in the drier parts of the country until 1960. Mesquite trees were regarded as beneficial plants as they provide fuel wood, shade and fodder. However, at least two species are now  widespread and cause problems in the northwestern part of the country. When mesquite forms dense and impenetrable stands, plants become smaller providing minimal shade and few pods and the root system use much of the scarce underground water. In an attempt to solve conflicts of interests, the biological control program is focused on agents that attack seeds, pods, flowers and flower buds, reducing the invasiveness and spread of mesquite, without affecting valuable attributes of the plants. The project was started in October 2002.

Studies to evaluate the host range of Coelocephalapion gandolfoi. were conducted. Adult feeding and oviposition preferences were evaluated confirming that the weevil is restricted to Prosopis species of Section Algarobia. The agent was shipped to quarantine at Pretoria, South Africa, for additional testing. The project is now concluded at SABCL.

FOR MORE INFORMATION CONTACT FERNANDO MC KAY fmckay@speedy.com.ar

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Cabomba caroliniana

Guillermo Cabrera

Cooperator: Mic Julien, CSIRO European Laboratory, Montferrier sur Lez, France, and Shon Schooler, CSIRO Entomology, Indooroopilly, Australia
CSIRO Entomology

Fanwort (Cabomba caroliniana Gray) is a small genus of strictly submerged aquatic plants from America. It is distributed, and considered native, in the neotropics and North America. However, considering the neoptropical distribution of the genus, it is probably naturalized in North America (Orgaard 1991). It is considered a weed in the U.S., Japan and Australia, and may have problematic status in southeast Asia (Mackey 1996). It was most probably dispersed by aquarists and aquarium suppliers who grew the plant, or disposed of them, in open water courses. 

This weed poses several problems: safety hazards for people practicing aquatic sports, health hazard from magnesium excedents during winter fallback of the plant; environmental problems related to excess of organic matter and eutrophication of water courses and catchments, competitive displacement of native plants and their associated fauna; and often severe hindrances to navigation, fishing and other large scale water uses (Mackey 1996). 

In Argentina, where it goes by the native name of Cabomba, it is cited from  the provinces of Buenos Aires, Rio Negro, Cordoba, Corrientes, Entre Rios, and Santa Fe (Bonetto & Hurtado 1998, Catálogo de las plantas vasculares de la Argentina 2002). Where at least two varieties are cited, var. caroliniana, and flavida (Orgaard 1991). It is not considered a weed in Argentina, or all of South America, for that matter. This is the first natural enemy survey on this plant.

Current research efforts are concentrated in the weevil Hydrotimetes natans. Adults feed on foliage, and the larvae mine the stems. The pupa develops in a kind of air tight cocoon attached to the stems. It has been collected at several locations in the province of Corrientes. It is a true swimmer/diver that can live under water for hours on end by holding a permanent air bubble surrounding its abdominal sternites. Field and laboratory host range studies indicated that it is specific to fanwort. The weevil was recently shipped to quarantine in Brisbane, Australia.

Annual Report 2007 
Annual Report 2008

FOR MORE INFORMATION CONTACT GUILLERMO CABRERA                                 gcabrera@speedy.com.ar

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Schinus terebinthifolius 

Fernando Mc Kay
Guillermo Cabrera
Marina Oleiro

Cooperators: Greg Wheeler and Ted Center, USDA-ARS-Invasive Plants Research Laboratory, Ft. Lauderdale, FL, USA.
IPRL, Fort Lauderdale, Florida

The BP was introduced in the U.S. during the late XIX century as an ornamental plant. At present, it is considered a high-priority target due to its widespread occurrence in Hawaii, California and Florida. First biocontrol efforts against BP were carried out in Hawaii during the 1950´s.  Three insects were released from South America: Episimus utilis Zimmerman (Lepidoptera: Tortricidae) in 1954, Lithraeus atronotatus Pic (Coleoptera: Bruchidae) in 1960, and Crasimorpha infuscata Hodges (Lepidoptera: Gelechiidae) in 1961; E. utilis and L. atronatus got established but exert only negligible control (Krauss 1962; Yoshioka and Martin 1991; Julien and Griffiths 1998; Hight et al. 2002). Additional surveys were conducted in Brazil during the 1980´s and 1990´s (Bennet and Habeck 1991, Medal et al. 1999). However, no insects have been released in Florida against BP. An accidental introduction from South Africa of a seed-feeding wasp, Megastigmus transvaalensis Hussey (Hymenoptera: Torymidae), was recorded in Florida (Habeck et al. 1989). The wasp is currently causing 30% seed mortality (Wheeler et al. 2001). The leaf feeder sawfly Heteroperreyia hubrichi (Hymenoptera: Pergidae) and the sap sucking thrip Pseudophilothrips ichini (Thysanoptera: Phlaeothripidae) were introduced in quarantine to conduct risk assessment studies (Hight et al. 2003). Petitions to release these agents have been submitted to the TAG. Although the release of the sawfly was authorized, the decision has been delayed until the impact of the toxins discovered in the larvae is assessed (Hight et al. 2002, Cuda, pers comm.). Additional host range studies of the thrip were requested by the TAG.  

In June 2004, a cooperative agreement was signed with the Invasive Plants Research Laboratory (USDA-ARS, Fort Lauderdale, FL.). Field surveys to discover potential biocontrol agents were conducted and important organisms were found : the leaf feeder sawfly, Heteroperreyia hubrichi (Hymenoptera: Pergidae), a seed feeder bruchid, probably Lithraeus (=Bruchus) atronotatus Pic, a leaf blotch miner, the weevil Apocnemidophorus blandus (a batch of insects was collected in March 2004 and taken to the quarantine facility in Gainesville, Fl.), and an unidentified eriphyoid mite. More recently, other organisms were found. The research is now focused on the Gracillariidae blotch leaf miner and the moth Tecmessa elegans (Lepidoptera: Notodontidae). T. elegans showed a wide host range within the Anacardiaceae species.

A new species of leaf miner moth, possibly Stigmella sp. (Nepticulidae) and an unidentified Gelechiidae leaf miner were found mining leaves of BP and BP and L. molleoides respectively.

Annual Report 2007 
     Annual Report 2008

FOR MORE INFORMATION CONTACT FERNANDO MC KAY fmckay@speedy.com.ar

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Egeria densa

Guillermo Cabrera

Cooperator: Ray Carruthers and Lars Anderson, USDA-ARS-Exotic & Invasive Weed Research Unit, Albany and Davis, CA, USA.
EIWRU, California

Egeria, commonly called Brazilian waterweed, is a South American genus of rooted, perennial, submerged plants in the family Hydorcharitaceae. The genus has two species, E. densa Planchon and E. najas Planchon, both amply distributed in all southern South America where they are not considered weeds, and therefore they have not been studied extensively. Consequently, little is known about their ecology and natural enemies. Egeria densa has weed status in North America, where it invades fresh water courses, forming dense patches that hinder navigation, fishing and other recreational water uses, and presents a severe ecological threat due to its invasiveness.

Surveys conducted in northern and central Argentina revealed that E. najas is more abundant than E. densa, at least in the northern regions. In samples of E. densa from Entre Ríos province, we found larvae of a pyralid (Lepidoptera), probably Paraponyx sp., mining the terminal shoots; several stem mines of Chironomidae; and of a species of shore fly in the genus Hydrellia (Diptera: Ephydridae). Apart from these species, many midge larvae, caddisflies, gastropods, and aquatic beetles were recovered. However, these are mostly probably saprophages or generalists of little interest from the biocontrol standpoint.

Current research is concentrated in Hydrellia nv. sp., found to attack Egeria throughout its distribution in Argentina. The fly was reared successfully in the laboratory, and tested for damage levels and host specificity. It can achieve heavy defoliation of the plant, both in the laboratory and in the field in its native range. Results indicate Hydrellia nv. sp. is a good candidate for the biocontrol of E. densa.

Annual Report 2007 
Annual Report 2008

FOR MORE INFORMATION CONTACT GUILLERMO CABRERA                                 gcabrera@speedy.com.ar   

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    Water primrose

Ludwigia hexapetala 

M. Cristina Hernández
Guillermo Cabrera
Gerardo Elsesser

Cooperator: Ray Carruthers and Brenda Grewell, USDA-ARS-Exotic & Invasive Weed Research Unit, Albany and Davis, CA, USA.
EIWRU, California

The genus Ludwigia includes 82 species, 20 of which are known to occur in Argentina. They are predominantly tropical herbs or shrubs. L. hexapetala, commonly called water primrose, is an aquatic perennial herb, formerly included in the L. uruguayensis group. Genetic variability within the genus was reported and the following two species are recognized:  L. grandiflora (hexaploid) and L. hexapetala (decaploid). L. hexapetala is native to southern South America, where it is widely distributed. It is also common in California. L. grandiflora is considered a nuisance in south-eastern U.S., and there is research underway for biological controls.

Preliminary surveys on Ludwigia spp. were conducted and the following species were collected and preserved: L. hexapetala, L. peploides peploides, L. peploides near glabrescens, L. elegans (Cambess.) Hara, L. bonariensis (Micheli) Hara, L. longifolia (DC) Hara, L. caparrosa (Cambess.) Hara, L. leptocarpa (Nutt.) Hara, L. octovalvis (Jacqs.) Raven, L. peruviana (L.) Hara, L. neograndiflora (Munz) Hara, and L. sericea (Cambess.) Hara.

Larvae found feeding on L. hexapetala, and on both subspecies of L. peploides were sampled and the adults obtained. Although the taxonomic identification is pending, the adults belong to the following taxa: 1) Coleoptera: Curculionidae: Auleutes sp.; Tyloderma sp.; Chrysomelidae: Lysathia sp., 2) Homoptera: Fulgoridae, 3) Thysanoptera, 4) Lepidoptera: Sphingidae, Pterophoridae, Tortricidae, and Pyralidae, 5) Hymenoptera: Pergidae: Lagideus sp., (Identification in progress by David Smith, Smithsonian Institution).  

Genetic and molecular studies, combined with traditional morphology and field explorations, are underway in order to clarify this problem and tackle the native fauna with specific knowledge of the group. These studies are partially funded by Dr. Hilda Díaz Soltero, USDA-Invasive Species Coordinator, Washington DC.

Annual Report 2007 
     Annual Report 2008

FOR MORE INFORMATION CONTACT CRISTINA HERNANDEZ crisher@speedy.com.ar

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Cardiospermum grandiflorum, Campuloclinium macrocephalum, Pereskia aculeata, Macfaydena ungis-cati

Fernando Mc Kay
Marina Oleiro

Cooperators: Arne Witt, David Simelane, and Andrew McConnachie, Agricultural Research Council, Plant Protection Research Institute, Pretoria and Hilton, South Africa, and Martin Hill, Rhodes University, South Africa
PPRI, South Africa

As part of a new strategy of targeting weeds at an early stage of invasion, a new agreement for cooperative research has been signed in January 2005 between the Plant Protection Research Institute (PPRI), Pretoria, South Africa and the SABCL. The main objective of this project is to search for and study host specific natural enemies of the emerging weeds (EW) Cardiospermum grandiflorum Sw. (Balloon vine), Campuloclinium macrocephalum (Less.) DC. (Pompom weed), and Pereskia aculeata Mill. (Barbados gooseberry).

Balloon vine (Cardiospermum grandiflorum) is a perennial slightly woody climber of the Soapberry family (Sapindaceae). Original from Tropical and Sub Tropical America (Panamá to Argentina), this tendril-bearing vine also occurs in Australia and Africa (Ferrucci 1991). Some of the organisms found were: Cissoanthonomus tuberculipennis Hustache (Coleoptera: Curculionidae) developing inside fruits; the “hairstreak moth” Chlorostrymon simaethis sarita (Skinner) (Lepidoptera: Lycaenidae), on both Cardiospermum grandiflorum and C. halicacabum (currently in quarantine facilities in Pretoria, South Africa);  a Pyralidae moth destroying the seeds; Gargaphia sp. (Hemiptera: Tingitidae) (was recently shipped to quarantine); the moth Apocera zographica and the fungus Phyllacora rimulosa

Pompom weed (Campuloclinium macrocephalum) is considered a serious invasive weed in South Africa (Henderson 2001). It has showy pink flower heads at the end of green to purplish aerial stems. The plant has a short woody rootstock that ends in thick tuber-like perennial roots, that enables the plant to survive fires, frost and drought conditions. Some of the organisms found on this weed were: the stem-boring, Zeale (=Adesmus) nigromaculatus (Coleoptera: Cerambycidae); Carmenta n. sp. (Lepidoptera: Sesiidae); Liothrips sp. (currently in quarantine facilities in Hilton, South Africa); Gelechiidae and a Pterophoridae moth, the fly Trupanea sp.. More recently, the moths Cochylis sp. and Adaina sp. and the thrips Liothrips tandililensis were shipped to quarantine for specificity testing

Barbados gooseberry (Pereskia aculeata) is a perennial leaf cactus, shrubby to clambering vine native to the West Indies and South America (Argentina and Brazil) (Henderson 2001). The plant has become a weed from garden and cultivation escape in Central America, Florida, Australia and South Africa.  Implementation of biological control program by PPRI researchers led in 1991 to the release of the leaf-feeding flea beetle Phenrica guerini (Coleoptera: Chrysomelidae). Insects are inflicting considerable damage at Port Alfred (Eastern Cape Province), but it has apparently not become established in other areas.

Initial field surveys in Argentina revealed the presence of a fruit-feeding moth (Lepidoptera: Crambidae: Pyraustinae). Considering the destroying capacity of this moth on the fruits of this plant, after confirming its identity, it would be worth evaluating its potential a as biocontrol agent against pereskia in South Africa.

Cat´s claw (Macfaydena unguis-cati) was recently included in the surveys for natural enemies. Current research is based on the weevil Apteromecus notatus and on an unidentified seed-feeding moth.

Annual Report 2007 
Annual Report 2008

FOR MORE INFORMATION CONTACT FERNANDO MC KAY fmckay@speedy.com.ar

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Solenopsis invicta & S. richteri 

Juan Briano
Luis Calcaterra
Laura Varone
Sonia Cabrera
Mariana Manteca

Cooperators:  Robert Vander Meer, Sanford Porter, David Oi, Steven Valles, Dewayne Shoemaker, USDA-ARS-Center for Medical, Agricultural, and Veterinary Entomology (CMAVE), Gainesville, FL, USA.
CMAVE, Gainesville

The red and black imported fire ants, Solenopsis invicta Buren and S. richteri Forel, respectively, where accidentally introduced into the United States from South America in the early 1900´s. The former infests 320 million acres in 12 southern states from Florida to California, also in Puerto Rico, other Caribean areas and Mexico. In 2001, S. invicta was discovered in Brisbane, Australia, and it has spread. In New Zealand, two incursions were detected in Auckland (2001) and Napier (2004), but apparently further dispersal was controlled. In 2003, S. invicta was detected in Taiwan and in 2005 in mainland China and Hong Kong.

Several organisms are under study for the biological control of the imported fire ants in the United States: the microsporidian pathogens Thelohania solenopsae (Microsporida: Thelohaniidae) and Vairimorpha invictae (Microsporida: Burenellidae), several species of the parasitoid fly Pseudacteon spp. (Diptera: Phoridae), the parasitic ant Solenopsis daguerrei (Hymenoptera: Formicidae), the micro wasps Orasema simplex and O. xanthopus (Hymenoptera: Eucharitidae), Allomermis solenopsii (Nematoda: Mermithidae), and a virus. Thelohania solenopsae, P. tricuspis, P. curvatus, P. litoralis, and P. obtusus  were released in the field in the United States and are being evaluated. The microsporidium V. invictae will be probably released in 2009. The flies P. nocens and P. cultellatus were recently shipped to quarantine in Gainesville and will be eventually field released in the near future.

Ecological interactions of fire ants with competitors ants and phorid flies are being evaluated in different habitats in Argentina. In addition, genetic studies are being conducted at CMAVE with material collected in South America to characterize the populations structure of the parasitic S. daguerrei to match their local populations with their fire ant hosts. Also genetic studies are being performed to detect the source population of the fire ants present in the United States and other countries.

In mid 2008, equipment and supplies were transferred from CMAVE Gainesville to conduct PCR studies and screening of potential fire ant viruses in Argentina. Surveys and assays will start in September 2008.

Annual Report 2007 
     Annual Report 2008
Imported Fire Ant Literature Database 

FOR MORE INFORMATION CONTACT JUAN BRIANO jabriano@speedy.com.ar

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Homalodisca vitripennis

Guillermo Logarzo
Florencia Palottini
Mariel Guala

Cooperators: Jesse de León, Beneficial Insects Research Unit, Weslaco, TX and Serguei Trapitsyn, University of California, Riverside, CA, USA
BIRU, Texas

The glassy-winged sharpshooter, Homalodisca vitripennis Say (Homoptera: Cicadellidae), is native to southeastern United States. Since the early 1990’s, this insect has spread dramatically, resulting in a very serious pest problem in the Central Valley and coastal viticulture regions in southern California. As other xylem feeders, GWSS is an effective vector of the bacterial plant pathogen, Xylella fastidiosa, the causal agent of the Pierce’s disease of grapes, the phoney peach disease in southern United States, the variegated chlorosis of citrus in Brazil, and the oleander leaf scorch in southern California. So far, only one biological control agent has been found, the small egg parasite, Gonatocerus ashmeadi Girault (Hymenoptera: Mymaridae). Although parasitism rates are usually very high (80-100%), suficient numbers of over-wintering adult sharpshooters remain in the field to produce problems the following season. It is clear that natural control has not been suficient to control the pest. More work is needed on GWSS biology, management and biological control, including foreign exploration for biological control agents in California.

In 2000, the SABCL started a survey of egg parasitoids of Tapajosa rubromarginata Signoret (Homoptera: Cicadellidae) and other proconiini sharpshooters related to GWSS in Argentina, Chile and Peru. Eight species of Gonatocerus (Mymaridae), one species of Paracentrobia, 2 species of Oligosita and 2 species of Zagella (Trichogrammatidae) were obtained.

Current research is focused on specificity studies of G. tuberculifemur both in the lab and in the field. Studies have been conducted also on functional response and climatic tolerance; surveys of egg parasitoids are being continued. After recent molecular, biological and morphological studies, results revealed the presence of two cryptic species in the G. tuberculifemur complex. Several species of Gonatocerus were shipped to Mission TX and more recently to Riverside CA for further testing under quarantine conditions. It is the intention to release the parasitoids in California.

Annual Report 2007 
     Annual Report 2008

FOR MORE INFORMATION CONTACT GUILLERMO LOGARZO glogarzo@speedy.com.ar

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Diabrotica spp. 

Guillermo Cabrera

Cooperators: Don Weber, Mike Athanas, USDA-ARS-Insect Biocontrol Laboratory, Beltsville, MD, USA.
IBL, Beltsville

The genus Diabrotica (corn rootworms and cucumber beetles) includes some of the most important row crop and vegetable pests of the Americas. In South America, the most common and problematic species are Diabrotica speciosa (Germar), that causes important damage in maize, cucurbits, potatoes, soybeans, and damage to the tender parts of almost every crop; Diabrotica viridula (F.), a pest of corn; and several species akin to the North American striped cucumber beetle (Acalymma vittatum (F.)), Acalymma albidovittata (Baly), Acalymma bivittula (Kirsch), and Acalymma bruchii (Bowditch), which cause significant damage to cucurbits.

The parasitoid Centistes gasseni Shaw has been collected in southern Brazil, eastern Paraguay, and northeast Argentina, in three Diabrotica species. The parasitoid Celatoria bosqi Blanchard was the first parasitoid described in Diabrotica spp. in South America, and large natural infestations have been observed. C. bosqi has been collected throughout the South American distribution area of its main host, Diabrotica speciosa (Germar), in an area that includes temperate and tropical lowlands, and semiarid to humid highlands. Both parasitoids thrive in subtropical to temperate climates similar to many parts of the U.S.A., suggesting they could be released as biocontrol agents only in those areas.

Cucurbitacins (Cucs) are triterpenoids, that are almost exclusive of the Cucurbitaceae. They serve the plant as chemical defense against phytophagy owing to their extreme bitterness and toxicity. However, they have been known for several years to have a strong feeding stimulant effect on Diabroticina. So they can be used combining them with toxicants in relatively small quantities, thus drastically cutting the overall quantity of pesticides incorporated to the crop system. At the SABCL we worked on sources of B Cucs; several potential sources of B Cucs were identified and tested and the most important were: Cayaponia spp., Cucurbita andreana, and Apodanthera sp.

We recently evaluated the effect of cucurbitacin rich extracts at different scales, from single release points to 1-ha applications. This evaluation required the implementation of a mark-release-recapture method, which demanded the evaluation of different marking techniques. The most suitable techniques were the use of fluorescent pigments dusted on the insects or added to the diet.

Annual Report 2007 

FOR MORE INFORMATION CONTACT GUILLERMO CABRERA gcabrera@speedy.com.ar

 

Cactoblastis cactorum 

Guillermo Logarzo
Laura Varone
Juan Briano
Florencia Palottini
Mariel Guala
Mariana Manteca

Cooperators: Stephen Hight, USDA-ARS-Insect Behavior and Biocontrol Research Unit, Tallahassee, FL, USA.
IBBRU, Florida

In late 2007, a project was started on biological control of the cactus moth, Cactoblastis cactorum. The objective is to identify host specific natural enemies in its native range of northern Argentina.  Cactoblastis cactorum is invading the southeastern US and attacking species of prickly pear cactus (Opuntia spp.). 

 Life table studies are being conducted in northern Argentina and comparisons of natural enemies of C. cactorum will be made between different habitats. Potential candidates include host specific egg parasitoids, egg-larval parasitoids, larval parasitoids, larval-pupal tachinids that have planidial larvae, which attack neonates before they enter pads, hymenopteran pupal parasitoids, and various larval pathogens.

General surveys for arthropods and pathogens attacking C. cactorum are being conducted in areas not used in the life history analysis. So far, the most frequent agents were the larval parasitoid Apanteles alexanderi (Hymenoptera: Braconidae) and the egg parasitoid Trichogramma pretiosum (Hymenoptera: Trichogrammatidae). In July 2008, a few locations were found infected with Nosema-like pathogens.

 Opuntia spp. attacked by cactus moths will be evaluated in various habitats, such as road sides, natural areas, ornamental plantings, empty lots, and/or abandoned plantations. 

Annual Report 2008

FOR MORE INFORMATION CONTACT GUILLERMO LOGARZO glogarzo@speedy.com.ar

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