Folgarait, P. J. y Goffré, D.

Frontiers in Fungal Biology. Special issue on Ant-Fungi Interactions  –  2023

Abstract: Pest ants are known for their damage to biodiversity, harm to agriculture, and negative impact on human welfare. Ants thrive when environmental opportunities arise, becoming pests and/or invading non-native areas. As social insects, they are extremely difficult to control using sustainable methods like biological control. The latter, although safer to the environment, acts slowly allowing the ants to use their individual and social defenses. Among biocontrol agents, fungal pathogens were proposed as promising, however, it is difficult to ascertain their success when the bibliography has not been reviewed and condensed. Therefore, this paper is the first in performing such task by analyzing publications mainly from 2000 to 2022 about the control of pest ants by fungi. From 85 publications selected, 77% corresponded to laboratory studies. Beauveria and Metarhizium were the genera most used in laboratory and field studies. Most of them included Acromyrmex and Atta leaf-cutter ants (LCA), and Solenopsis fire ants. From laboratory experiments, we evaluated how ant net mortality was affected by ant and fungal species, and also by origin, concentration, and inoculation technique of the fungal strains tested. Beauveria bassiana and Metarhizium anisopliae produced the greatest mortality, along with the inoculation spray technique and fungal strains collected from ants. There was a positive relationship between ant mortality and fungal concentration only for those studies which evaluated more than one concentration. Twenty field experimental studies were found, covering 13 pest species, mainly LCA and Solenopsis invicta. Only B. bassiana was tested on Solenopsis, M. anisopliae was mostly used for Acromyrmex, and M. anisopliae or Trichoderma were mainly used with Atta species. The median control field efficiency varied from 20% to 85% for different fungi and ant genera. When grouping all fungal species together, the median control efficiency seemed to be better for Acromyrmex (67%) than for Atta and Solenopsis (both 43%). Our review shows that, at this stage of knowledge, it is very difficult to extrapolate any result. We offer suggestions to improve and standardize laboratory and field experimental studies in order to advance more efficiently in the fungal control of pest ants.

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Goffré, D. y Folgarait, P. J.

Neotropical Entomology 52(4):731-741  –  2023

Abstract: Purpureocillium lilacinum (Hypocreales: Ophiocordycipitaceae) is a cosmopolitan fungus not only pathogenic to insect and nematode hosts but also to other fungi. Although having one organism with multiple effects would be desirable in a biocontrol strategy, few studies have looked at the multiple roles one strain could play. This work shows how three strains of P. lilacinum, previously proven to be entomopathogenic to leaf-cutter ants (LCA), could degrade several strains of Leucoagaricus sp., the fungus cultivated by LCA as their food source. We isolated four strains of Leucoagaricus sp. from Acromyrmex and Atta LCA species, and we determined their species molecularly, as well as their clade identity (Leucoagaricus gongylophorus, clade-A). We observed the effects on growth rates on Petri dishes and the interaction of microscopic structures of both fungi on slides. All three P. lilacinum strains inhibited the growth of L. gongylophorus. They also degraded all L. gongylophorus isolated from the Acromyrmex species, causing hyphae expansion and degradation of the cell wall. However, only one of them succeeded in degrading the L. gongylophorus strain isolated from the Atta species. The results confirm the damage to the hyphae of ant cultivars and highlight the need for future studies that reveal whether such behavior is due to P. lilacinum’s mycoparasitic behavior. Using a single P. lilacinum strain with a dual function that includes the degradation of the cultivar of LCA of both genera would be a very promising strategy for the biocontrol of one of the worst herbivore pests in the Neotropics.

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Folgarait, P.J. y Goffré, D.

Journal of Invertebrate Pathology 186 DOI 10.1016/j.jip.2021.107685.  –  2021

Abstract. Conidiobolus lunulus is a recently described entomophthoralean species isolated from leaf-cutter ants. This fungus discharges not only primary but also secondary conidia and microconidia of different shapes. Because nothing was known about the biology of the fungus, and its interactions with hosts, we first evaluated if its pathogenicity against leaf-cutter ants changes with the fungal age (time grown in vitro), and if it is related to the conidial structures produced. Afterwards, we tested its virulence at three combinations of temperature and relative humidity. In addition, we noted all visible causes of death by recovering different microorganisms from the dead, non-sterilized, ants to evaluate C. lunulus virulence when pathogens carried naturally by the ants were present. Finally, we used the conditions that lead to the highest mortality to evaluate fungal virulence to other host species, including non-leaf-cutter ants. Results indicated that C. lunulus was pathogenic from a culture age of 1 to 5 days, with a peak at 2-days-old, from which we registered median lethal times of 1–2 days and 85% of the cadavers with fungal conidiation. Our results suggest that primary conidia and moon-shaped microconidia were infective. Evaluations of mortality using 2-days-old cultures on several leaf-cutter ant colonies showed 1) significantly faster mortality of C. lunulus inoculated ants in comparison to controls, 2) significantly greater and faster mortality at 23.7 °C than at 21.2 °C, 3) significantly higher and faster mortality at 88% than at 57% RH, and 4) a significant reduction of other pathogens in C. lunulus inoculated ants in comparison to controls. C. lunulus was highly specific to leaf-cutter ants, as hardly any increase in mortality was observed on inoculated ants, and no conidia were recorded on cadavers of the other three non-leaf-cutter ant species tested. Our results highlight that C. lunulus is a very promising biological control agent against leaf-cutter ants.

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Folgarait, P.J. y Goffré, D.

Entomologia Experimentalis et Applicata DOI: 10.1111/eea.13078  –  2021

Abstract: The alternative use of biological control agents (BCAs) against leaf-cutter ants (LCAs) is in increasingly high demand due to the negative consequences of traditional pesticides. Regarding LCAs, BCAs include entomopathogens that infect them, and mycopathogens that kill the fungi cultivated by these ants. The simultaneous use of multiple BCAs requires that the agents do not negatively affect each other. To test this hypothesis, we set up laboratory assays to evaluate in vitro interactions among an entomopathogen [Beauveria bassiana (Bals.-Criv.) Vuill.], a mycopathogen [Trichoderma virens (JH Mill., Giddens & AA Foster) Arx], and the LCA-cultivated symbiotic fungus Leucoagaricus sp. We also tested the BCAs in the field by offering them in three types of bait to Acromyrmex lundii Guérin-Méneville (Hymenoptera: Formicidae), in order to evaluate: (1) the control efficiency of these BCAs on LCA field colonies, and (2) whether there was delayed rejection of baits placed sequentially. Our in vitro results showed that T. virens was not affected by Leucoagaricus sp. or by B. bassiana, whereas B. bassiana was negatively affected by the mycopathogen and the cultivated fungus, probably due to substrate competition. Leucoagaricus sp. was not affected by B. bassiana but it was negatively affected by T. virens, as predicted, destroying the cell walls of the cultivated fungus. The field study showed 62.5% control of LCA after applying the three types of bait on three occasions throughout 27 weeks, without detecting any delayed rejection effect. Due to the variability registered in colony inactivity, we propose a continued inactivity of 13 weeks as a criterion for A. lundii control. We discuss the importance of continuous long-term assessments of BCAs on LCA control.

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Goffre D,  A. B. Jensen , C. C. Lopez Lastra , R. A. Humber & P. J. Folgarait

Mycologia, DOI: 10.1080/00275514.2020.1816387 –  2020

Abstract: Entomophthoralean fungi with pathogenic abilities to infect social insects are rare. Here, we describe a fungus isolated from leafcutter ants. Morphologically, the fungus has spherical primary conidia and two types of microconidia: one with the same shape as the primary conidia and another with an elliptical to half-moon shape. The fungus also produces villose conidia known previously only from Conidiobolus coronatus. A multilocus phylogenetic analysis was performed with nuc rDNA sequences from three regions (28S, 18S, and internal transcribed spacer [ITS]). Our isolates are distinguished as a new species, described here as Conidiobolus lunulus, and is more closely related to C. brefeldianus than to C. coronatus, despite the greater morphological resemblance to the latter. Morphological differences, unique phylogenetic placement, and isolation from an altogether new host support this finding. This is the first record of an entomophthoralean species isolated from leafcutter ants.

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P.J. Folgarait, D. Goffré y A. Giraldo Osorio.

Biocontrol Science & Technology 30: 996-1005 –  2020

Abstract: Leafcutter ants are a serious pest for forestry plantations and crops in Latin America. They have been traditionally controlled using chemical synthetic pesticides, which are known to have many negative effects to non-target organisms and the environment. Therefore, there is an urgent need for the development of alternative strategies of control, among which the biological control using fungal pathogens is a promising one. We evaluated in laboratory 3 strains of Beauveria bassiana (B5, B6, B7) against workers from 4 to 7 field colonies from 5 species of Acromyrmex leafcutter ant species which are considered pests in the region. Our results showed that all strains were pathogenic, although there are some ant species that turned out to be more susceptible either due to their intrinsic immunity or the natural load of pathogens they carried. The three strains were similarly effective for 3 of the 5 species, A. ambiguus, A. crassispinus, and A. lundii, being responsible for more than 80% of their mortality overriding the effect of their natural pathogens. Only strain B6 was able to kill a similar percentage of ants of A. heyeri, and strain B7 half of them. B5 in A. heyeri, as well as all three strains in A. lobicornis, were responsible for up to 30% of the mortality, but with the additive effect of the pathogens naturally brought by these ants accounted for a 70% of their mortality. We recommend using B6 to test the control of Acromyrmex leaf-cutting ants in the field.

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P.J. Folgarait, D. Goffré y A. Giraldo Osorio.

Bulletin of International Organization for Biological and Integrated Control 150:9-15. –  2020

Abstract: Leaf-cutter ants are a serious pest to forestry plantations and crops in Latin America. They have been traditionally controlled using chemical synthetic pesticides, which are known to have many negative effects to non-target organisms and the environment overall. Therefore, there is an urgent need for the development of alternative strategies of control among which the biological control using fungal pathogens is a promising one. In this study we evaluated 3 strains of Beauveria bassiana against 5 species of Acromyrmex leaf-cutter ant species which are considered pests. Our results showed that all strains were pathogenic, although there are some ant species that turned out to be more resistant or more susceptible. Each of the strains exhibited different efficiency for two of the ant species, but for the other three they were equally effective with high percentages of recovery (more than 80%). Considering several aspects of the hygienic behaviours of this group of ants, and the characteristics of an inundative biological control strategy, several applications of different biological agents will be needed to control them. Then, taking into account our results, our recommendation is to use the three strains in a sequential fashion in order to avoid the lack of efficiency of any of the strains against one particular ant species.

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P.J. Folgarait, R.M. Plowes, C. Gomila, y L E. Gilbert. 

Florida Entomologist, 103(1): 9-15 –  2020

Abstract: The high diversity within a guild of Pseudacteon Coquillet (Diptera: Phoridae) parasitoid flies hosted by the red imported fire ant, Solenopsis invicta Buren (Hymenoptera: Formicidae), may be based on several niche axes, including host size specialization, host location cues, climatic responses, and tolerances. The recently described species, Pseudacteon obtusitus Plowes, Folgarait, and Gilbert (Diptera: Phoridae), is one of the smallest species in this group (with a thorax width of only 0.3 mm), and appears to locate ant hosts on foraging trails as well as at nest disturbances. Here we examine the ecology, phenology, and development of this parasitoid at sites in Corrientes, Argentina. Pseudacteon obtusitus has 2 seasons of peak abundance, and exhibits low tolerance for cold temperatures or extended cold periods. It preys on the smallest ant workers (typically 0.6 mm head width) independent of the ant size offered, and has a male biased sex ratio (mean 2.78:1). Developmental times ranged from 35 d at 27 °C to 44 d at 22 °C. This species holds interest for inclusion among the multi-species assemblage of parasitoid flies considered for biological control of S. invicta in its invasive range in North America. La gran diversidad dentro del gremio de moscas parasitoides del género Pseudacteon Coquillet (Diptera: Phoridae), específicas de las hormigas de fuego, Solenopsis invicta Buren (Hymenoptera: Formicidae), puede estar basada en varios ejes de nicho incluyendo una especialización por el tamaño del huésped, claves de localización del huésped y respuestas climáticas o tolerancias. La especie recientemente descripta, Pseudacteon obtusitus Plowes, Folgarait, Gilbert (Diptera: Phoridae), es una de las más pequeñas de este grupo con un ancho de tórax de 0.3 mm y parece localizar a las hormigas huésped en los caminos de forrajeo así como en nidos disturbados. En este trabajo se examina la ecología, fenología y desarrollo de esta especie en sitios de Corrientes, Argentina. Pseudacteon obtusitus tiene 2 picos de abundancia y posee poca tolerancia a las temperaturas bajas o períodos largos de frío. Esta especie ataca a las obreras más pequeñas (típicamente de 0.6 mm de ancho de cabeza) independientemente del tamaño de huésped ofrecido, y tiene una relación de sexos sesgada hacia los machos (promedio 2.78:1). Los tiempos de desarrollo varían de 35 días a 27 °C hasta 44 días a 28 °C. Esta especie es interesante para incluirla en el ensamble multi-específico de moscas parasitoides consideradas para el control biológico de Solenopsis invicta en su rango de invasión en América del Norte.

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Goffré, D. y Folgarait, P. J.

Entomologia Experimentalis Et Applicata 167: 939-949 –  2019

Abstract: Phorid flies (Diptera: Phoridae, Metopinini) are natural enemies of leafcutter ants (Hymenoptera: Formicidae, Attini), which are among the most important pests in the Neotropical region. These parasitoids lay their eggs inside worker ants, causing the death of the parasitized ants, and the oviposition attacks on foraging workers interfere with the collection of vegetal material used in fungal gardens, thereby affecting the whole colony. However, because of the large number of ants per colony, more than one type of biological control agent is needed to have a significant impact. We collected parasitized leafcutter ants Acromyrmex lundii (Guérin-Méneville), Acromyrmex heyeri (Forel), and Acromyrmex ambiguus (Emery) from various places in Argentina and reared their parasitoids. We recorded developmental times, host and phorid sizes, and other aspects of the biology of the phorids Apocephalus neivai Borgmeier, Apocephalus noetingerorum Brown & Disney, Myrmosicarius gracilipes Borgmeier, Myrmosicarius catharinensis Borgmeier, Myrmosicarius crudelis Borgmeier, and Myrmosicarius cristobalensis Disney et al. This is the first record of A. ambiguus, an important pest of pine plantations, being a host of phorids. We found the first cases of gregarious parasitoidism of a parasitoid with no-free pupae: M. catharinensis on A. lundii ants. We also evaluated the effect on pupal survival of two cosmopolitan fungi, Beauveria bassiana (Balsamo) Vuill. and Trichoderma lentiforme (Rehm) Chaverri et al., which are also considered as potential biological control agents of leafcutter ants. Suspensions of conidia were tested on Myrmosicarius and Apocephalus parasitoid pupae of different ages. No negative effect on pupal survival was found under either fungal treatment. Therefore, the use of both natural enemies separately but simultaneously, or the introduction of fungi-inoculated pupae in the pest habitats, seems to be a promising strategy for the multiple biological control of leafcutter ants.

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Folgarait P.J., Guillade A.

En Hormigas de Colombia. Editor Fernandez F, Guerrero R, Delsinne T. Universidad Nacional de Colombia, Bogotá, Colombia, pp: 255-318.

Abstract: Las hormigas son uno de los grupos de insectos más comunes en los ecosistemas terrestres del planeta, importantes agentes de la dinámica y estructura de bosques, agrosistemas e incluso ambientes antrópicos. En el mundo Colombia ocupa un lugar destacado en diversidad, con 11 subfamilias, 105 géneros y unas 1200 especies descritas. El propósito del libro es ofrecer información actualizada en aspectos de sistemática, filogenia, morfología, métodos de captura y estudio y biología de las hormigas en general. Así como sinopsis de las especies conocidas del país, con claves y diagnosis para las subfamilias y géneros, incluso para las especies esperadas; esta incluye distribución por departamentos. El presente libro es el resultado de 30 años de investigación, con 37 capítulos escritos por 64 autores de 7 países; la mayoría de ellos autoridades mundiales en sus campos de acción.

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Marfetán, A., Romero, A., Cafaro M. y Folgarait P. J.

Mycotaxon, 133: 569-589 –  2019

Abstract: Escovopsis atlas, E. catenulata, E. longivesica, E. primorosea, and E. pseudoweberi spp. nov. are described from fungal gardens of higher attine ants in Argentina. All these species possess clear diagnostic features: E. atlas characterized by subglobose vesicles; E. catenulata by the presence of claviform vesicles forming short chains; E. longivesica by longer vesicles than the rest of the species; E. primorosea by pink coloration of colony in mCYA medium; and E. pseudoweberi by the smallest conidia known in the genus.

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Elizalde L., Guillade A. C., y Folgarait P. J.

Acta Oecologica; 93: 21-29. –  2018

Abstract: Resource segregation by species is a cornerstone ecological concept that may result from several processes such as interspecific competition, and can help structuring communities, in particular parasitoid communities. Phorid parasitoid flies that use ants as hosts usually employ one host per individual parasitoid, and thus the pressure for segregating the host resource should be high. At a particular community, these parasitoids might segregate resources by temporal differences in activity patterns, using different host species or nests from those available. Even if parasitoid species coexist on the same nest, they can take advantage of worker polymorphism and task division, searching for ants performing different tasks at different microsites of the same nest. Here we evaluated the segregation of parasitoid species in these hypothesized axes using leaf-cutting ant phorid parasitoids as a model system. We analyzed temporal data collected at two localities with contrasting host species richness; and compared parasitoid co-occurrence at the different niche axis. For most of the hypothesized niche axes tested we found either no departures from random expectations or significantly more niche overlap than expected by chance, ruling out the existence of biologically relevant host resource segregation in this system. However, there was evidence of segregation for some species, since one parasitoid species was only found in winter and another species showed a negative correlation of its abundance over nests with other two species. Furthermore, we found that several species were flexible in host use; Atta phorids varied in average host sizes preferred, whereas Acromyrmex phorids that were generalists were able to use different host species or microsites for host location. From an applied perspective, these results are encouraging when selecting species for the control of leaf-cutting ants because parasitoids coexistence seems to be unaffected by their overlap in niche dimensions.

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Elizalde L., Patrock R., Disney H. y Folgarait P. J.

Ecological Entomology; 43: 114-125 –  2018

Abstract:

1. Parasitoid–host interactions are important components of ecological communities. Although parasitoid–host interactions are strongly shaped by evolutionary history, the abundance of both the parasitoid and the host may have a role in determining the nature of the interaction once phylogenetic relationships are considered.

2. Leafcutter ants are hosts of phorid parasitoids and represent a well-defined and specialised module within a larger network of ant–symbiont interactions. A low specificity host taxa and a positive association between host abundance and parasitoid interaction frequency were expected due to the close phylogenetic relatedness of the hosts.

3. The interactions among all species of leafcutter ants and their parasitoids were quantified in two localities with different species richness. This study also characterised the spatial-temporal variability of these interactions, determined the patterns of parasitoid specificity and host selection, and tested for an association between host abundance and parasitoid interaction frequency.

4. Contrary to expectation, most parasitoid species were highly specialised and interaction frequency for parasitoid species was not related to host abundance. All host ant species were attacked by more than one phorid species. Some phorid species used more than one host species and showed preference for the same species over space and time, suggesting that there are physiological and/or behavioural restrictions on host use.

5. These results show that there is a tendency for specialisation even when hosts are highly similar in their ecology. From a biological control perspective, these parasitoids may be effective candidates, due to the high specificity of some species and little host-use variation through time.

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Goffré D., Cavallo E., Cavalitto S. F. y Folgarait, P. J.

Biocontrol Science and Technology; doi /10.1080/09583157.2018.1479730. –  2018

Abstract: Leaf cutter ants are one of the most important pests to agriculture and forestry in the Neotropics. One environmentally friendly solution to control them is biological control with the use of conidia of some fungi, such as Beauveria bassiana. We tested several isolates of this fungus (obtained from leaf cutter ants) by inoculating ants from seven colonies of Acromyrmex lundii with 5 × 10⁶ conidia ml⁻¹ suspensions. All the isolates proved to be good controllers, but isolate 5 (B5) was found to be the best performing option, because it caused the death of 92.3% of the ants in 4–5 days. Isolate 7 (B7) was the second-best option and used for comparative purposes. Further assays were performed with the isolate B5 to optimise yield production. Three types of rice (brown, parboiled and white rice), soybean hull and yerba mate (Ilex paraguariensis leaves) were tested as substrates, and following that, different conditions of solid-state fermentation (SSF) were changed so as to select the most productive combination. Among treatments, we selected brown rice as substrate and a temperature of 28°C and 75–85% relative humidity in the SSF chamber because this allowed a production of 6.4 × 10⁸ and 1.2 × 10⁹ conidia of B5 and B7 per gram of final substrate with a 98% and 97.5% of germination, in 10 days, respectively. The differences in yield obtained under the same conditions for both isolates show that yield is isolate-dependent. A description of the customised design of the SSF chamber used is included.

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Goffre D. y Folgarait P. J.

Insectes Sociaux; 65: 103-115. –  2017

Abstract: To our knowledge, this work is the first large-scaled, systematic survey of potential entomopathogens associated with worker ants of several Acromyrmex species. The study was performed at nine sites located in five Phytogeographical Provinces across Argentina. We recorded 28 species of fungi with entomopathogenic behaviour, which infected 24.3% of the 4737 collected ants from 94 colonies. Fusarium oxysporum and F. solani were the most widely distributed, followed by Purpureocillium lilacinum and Beauveria bassiana. The occurrence of species across nests within the same site varied from null to 98%. We did not detect any systematic association between fungi and site, Phytogeographical Province or ant species. Instead the microhabitats that surround each nest appear to play an important role in defining entomopathogen communities. We found that climatic variables like maximum temperature, dew point, and relative humidity helped to account for the distribution of these fungi at the site scale. Besides, colonies from undisturbed sites showed higher abundance of infections with entomopathogens than those from disturbed ones. These results greatly improve the knowledge of the ecology of the filamentous fungi associated with leaf-cutting ants. In addition, we proposed that the combination of the entomopathogen virulence and the resistance of ant colonies may be an important but overlooked effect influencing the diversity of entomopathogens.

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Guillade. A, Goffré D. y Folgarait P. J.

Revista de la Sociedad Entomológica Argentina; 76: 50-54.  –  2017

Abstract: Leafcutter ants are one of the most important crop pests in the Neotropics.
In the present study, several specimens were collected from four provinces in Argentina
in order to determine the species of phorid flies parasitizing them. We report our
findings on seven phorid species, Apocephalus neivai Borgmeier, Ap. noetingerorum
Disney, Neodohrniphora unichaeta Disney, Myrmosicarius catharinensis Borgmeier, M.
cristobalensis Disney, M. crudelis Borgmeier and M. gracilipes Borgmeier, over the
leafcutter ants Acromyrmex ambiguus Emery, Ac. crassispinus Forel, Ac. heyeri Forel, Ac.
lobicornis Emery and Ac. lundii Guérin. All the known hosts and geographic ranges for
these seven phorids in Argentina are provided. e seven phorid species represent new
records for all the provinces studied, expanding their geographical ranges; furthermore,
we establish a total of eleven new host-parasitoid interactions. Our data expand the
knowledge of this little studied system and provide important considerations for the
potential use of these parasitoids as biological control candidates of the leafcutter ants.

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Armando N. G., Marfetán J. A. y Folgarait, P. J.

Darwiniana, nueva serie, 5: 72-82. –  2017

Abstract: The aim of this work is the morphological and molecular identification of five species of Trichoderma associated with leaf-cutting ant nests of the genera Acromyrmex present in Argentina. The species identified were T. lentiforme, T. inhamatum, T. virens, T. koningiopsis and T. aff.neotropicale resulting in the first record of T. lentiforme and T. inhamatum associated with leaf-cutting Acromyrmex ants, in particular with Acromyrmex lobicornis and Acromyrmex lundii for the first one and with A. lobicornis for the second one. Moreover, T. lentiforme represents the first record for Argentina. In this work we extend the measurements of the conidia and the conidiophore and contribute with additional of the distribution of the species of Trichoderma in this country. Photographs illustrating conidiophores, conidiogenous cells, conidia, and colony phenotype are provided for each species.

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Marfetán J. A. y Folgarait P. J.

Ecología Austral, 27: 449-461. –  2017

Abstract: Attine ants are a monophyletic group comprising more than 230 species, distributed exclusively in the New World. All higher Attini ants depend on the cultivation of fungus gardens for food, and those gardens are continuously exposed to alien microorganisms. The present work describes, for the first time, the composition, relative frequency and the richness of the fungal species comprising the mycobiota from the garden of the most abundant Acromyrmex species from different regions of Argentina. We also compared, using a multivariate approach, the mycobiota composition with the purpose of testing two hypotheses: 1) whether mycobiota is defined by the ant species, or 2) whether mycobiota is determined by the geographical region. We found that each fungal community had a particular composition and abundance: the species that were highly frequent in a community or site, could be rare or altogether absent in another community or site. Species richness, as well as the theoretical maximum richness, also changed with locations. Furthermore, we found that different ant species at the same site had similar mycobiotas, whereas the same ant species in distant locations had only a few fungal species in common. Therefore, we concluded that mycobiota composition changed considerably with geographical site and was not dependent on the ant species. Our results provide an additional understanding of the leaf cutting-ants system, confirming that the garden of leaf cutting ants nests is a complex and dynamic fungal community which is dependent on the site where it was located.

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Elizalde, L., M. A. Fernández, A. C. Guillade, y P. J. Folgarait.

J. Pest Science 89: 403-411. –  2016

Abstract: The damage to plantations by pests is often determined by perceptions rather than objective data, resulting in excessive use of pesticides. Leafcutter ants are considered important pests to plantations in America. We evaluated the difference in Pinus taeda biomass consumption by four Acromyrmex leafcutter ant species which co-inhabit plantations of this pine species. These ants exhibit morphological and behavioral differences, i.e., Ac. heyeri has mandibles adapted to cut monocots, while the other species cut dicots, which may result in differences in their consumption of pine. We collected the plant biomass that ants carried into their nests and recorded the foraging activity in different seasons throughout a year. The P. taeda biomass carried into leafcutter nests was less than 20 % compared to total plant biomass. Colonies with greater foraging activity carried a greater amount of total biomass, but they did not carry more pine biomass. The leafcutter ant species studied differed in their use of pine biomass, but not of total biomass. Acromyrmex ambiguus and Ac. crassispinus were the species carrying the greatest amount of pine biomass and with more colonies using pine, whereas very little amounts of pine were carried by Ac. heyeri and by very few colonies. Thus, leafcutter ant species do not cause the same damage to pine plantations. Our results also highlight the importance of pest management strategies based on a thorough knowledge of the biology of the species, including those characteristics which can predict the use that each species will make of the plantation.

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D. Goffré y P.J. Folgarait.

Journal of Invertebrate Pathology 130: 107–115. – 2015

Abstract: Many leaf-cutter ant species are well known pests in Latin America, including species of the genera Acromyrmex and Atta. An environmentally friendly strategy to reduce the number of leafcutter ants and avoid indiscriminate use of chemical pesticides is biological control. In this work we evaluated the effectiveness of a strain of the entomopathogen Purpureocillium lilacinum, against worker ants from six Acromyrmex lundii field colonies, after immersions in pure suspensions at a concentration of 1 × 10⁶ conidia ml⁻¹. Survival of ants treated with P. lilacinum was significantly lower than that recorded in controls, and median lethal time (LT₅₀) was 6–7 days. P. lilacinum was responsible for 85.6% (80.6–89.7) of the mortality in inoculated ants, in which we found that the percentage of other entomopathogens that naturally infected ants decreased also, suggesting a good competitive capability of the fungus. Horizontal transmission to non-inoculated ants was also evidenced, given that 58.5% (41.9–64.2) of them died because of P. lilacinum. Moreover, we tested pathogenicity for three concentrations of this strain (1.0 × 10⁴, 10⁶ and 10⁸ conidia ml⁻¹) and found a significantly faster mortality of ants and greater median percentage of infection at 10⁸ conidia ml⁻¹ of P. lilacinum. CL₅₀ value was 2.8 × 10⁵ conidia ml⁻¹. We thus propose the use of P. lilacinum as a biological control agent of leafcutter ants in crops and plantations.

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Marfetán, Ariel; Romero A. y Folgarait, P. J

Fungal Ecology 17:52-61 – 2015

Abstract: Attini are the only ants that use fresh plant material to cultivate species of Leucoagaricus, which are their source of nutrition. Escovopsis species are specialized mycoparasites of Leucoagaricus sp. and Escovopsis parasitism has a negative impact on the health of the ants’ colonies. The goals of this work were: to test if the virulence of different isolates of Escovopsis weberi were the same across Leucoagaricus sp. and to analyze if structural mechanisms were related to variation in the virulence of E. weberi isolates. All E. weberi isolates were able to parasitize isolates of Leucoagaricus spp. but with striking differences in virulence, and it was shown that the contact between hyphae of both fungi was the main process that generates the degradation of Leucoagaricus isolates. Additionally, the two most virulent isolates produced hook-like protuberances, increasing the damage caused to its target. Finally, E. weberi was re-classified as a destructive biotrophic parasite.

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Guillade A.C. y Folgarait, P. J.

Agricultural and Forest Entomology17: 113-119. – 2014

Abstract: 

1. Leafcutter ants are considered the most important herbivores in the Neotropics. Atta vollenweideri is a rangeland pest that competes with cattle for grass, reducing the carrying capacity of pastures.
2. However, there is much controversy regarding their degree of herbivory, pest status and competition with cattle. Furthermore, their economic injury level (EIL) has not been determined.
3. We studied A. vollenweideri in competition with cattle in a natural pasture in Argentina, quantifying primary productivity, as well as herbivory by ants alone and together with cattle. Productivity and herbivory by ants were contrasted with cattle dietary requirements under two grazing regimes. We estimated the first EIL for leaf-cutting ants in rangelands.
4. Productivity was highly variable throughout the seasons. Competition between ants and cattle was evident during the low productivity periods, with evidence of ants being more affected by cattle unless ants store food during the productivity peak in summer and autumn.
5. The EIL was 0.29 ant nests per hectare, although it likely overestimates the importance of these ants as pests. We discuss the shortcomings of a classic EIL formula for estimating the damage potential of social insects.

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Guillade A. C. y Folgarait P. J.

Entomologia Experimentalis et Applicata. 154: 53-61 – 2014

Abstract: Leafcutter ants in the genus Atta (Hymenoptera: Formicidae: Attini) are considered major pests of agriculture and forestry in the Neotropics. Phorid flies (Diptera: Phoridae) have been proposed as viable candidates for biological control of ants because of the importance of their trait-mediated effects on their hosts. However, the impact of different densities of phorid flies has never been assessed in the field. Experiments were conducted by isolating 3-m sections of Atta vollenweideri Forel foraging trails with tunnels, and sampling ants in trails with 0, 1, or 4 Eibesfeldtphora trilobata Disney female parasitoid flies. Samples were collected every 30 min from these trails. We also collected a sample before introducing the parasitoids and another one 30 min after removing them from the trail. We measured traffic of ants on the trails, weight and type of plant material transported, and the proportion and size of the workers collected. The presence of phorids on the trails reduced the ant traffic and amount of plant material transported into the nests and decreased the proportion of workers on the trails in the size range preferred as hosts by the flies. The effect on worker size, as well as the lag effect recorded after phorids were removed from the tunnels, was more pronounced with four phorids. The presence of phorids also affected the weight of monocotyledon and dicotyledon material transported. Even at the minimum density possible, phorids significantly influenced a key aspect of the colony life, the food intake through foraging. From an applied point of view, our results show that releases of these phorids into the field should not necessarily involve many individuals to reduce foraging by A. vollenweideri, making them potentially useful candidates for biological control of these ants.

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Guillade A. C. y Folgarait, P. J.

Environmental Entomology 43:458-466 – 2014

Abstract: Phorid flies have been considered viable options for biological control of leaf-cutter ants because they are highly specific to these hosts, producing direct mortality and also affecting the normal functioning of colonies. Designing protocols for mass rearing of these insects requires knowing the temperature and humidity conditions that optimize their development in terms of duration, survivorship and longevity of adults. We reared Apocephalus setitarsus Brown, Eibesfeldtphora trilobata Disney, and Myrmosicarius brandaoi Disney, which are specific leaf-cutter ant parasitoids of Atta vollenweideri Forel, and Apocephalus neivai Borgmeier and Myrmosicarius catharinensis Borgmeier, which are parasitoids of Acromyrmex lundii Guérin-Méneville. Phorids were maintained under one of five different rearing conditions, 20°C high humidity (20HH), 24°C low and high humidity (24LH and 24HH), and 28°C low and high humidity (28LH and 28HH). Flies from all species could complete their development under all the conditions tested. As expected, the 20HH treatment significantly lengthened all developmental periods in all species, whereas the shortest duration was achieved under 28HH. Although pupal survivorship was highest at 24HH, the greatest longevity of adults was achieved at 20HH. Percentage of pupae obtained and pupal survivorship also exhibited the highest values at 24HH. The rearing efficiency index was highest for all species at 24HH. Therefore, we suggest this temperature and humidity combination as the most suitable for rearing these species, whereas the 20HH treatment is ideal for maintaining adults for longer periods, which would be advantageous for synchronizing matings and mass releases of adults in the field.

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Guillade A. C. y Folgarait, P. J.

Journal of Economic Entomology.107:105-114 – 2014

Abstract: In southern South America, Atta vollenweideri Forel (Hymenoptera: Formicidae) is a significant pest of several crops and forestry, also considered to reduce the carrying capacity of pastures. The most usual control method used in Latin America is the application of synthetic pesticides, mainly chlorpyrifos and fipronil. However, no studies have assessed the effects of these agrochemicals on natural enemies of ants. We aimed to evaluate the efficiency of these pesticides on leaf-cutter ants’ control and to test their effect on phorid fly parasitoids. Chlorpyrifos failed to exert complete control over ant colonies in the field and was gravely detrimental to specific parasitoids, reducing their percentage of parasitism, pupal survivorship, and adult longevity. Fipronil, however, exerted complete control over the treated colonies. Laboratory tests using both pesticides, either on ants from foraging trails or on pupariae, showed that chlorpyrifos and fipronil decreased larval and pupal survivorship, as well as adult longevity of parasitoids, in comparison to controls. In conclusion, these pesticides will likely affect parasitoids with regard to their reproductive capacity, leading to the decreased levels of natural parasitism observed in the field after treatments. We discuss why neither pesticide should be taken into account for integrated pest management programs.

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Folgarait, P. J.

Psyche. Article ID 539780, 10 pages. – 2013

Abstract: This review updates and summarizes the current knowledge about the interaction of leaf-cutter ants and their parasitoids by
providing comparable data for Acromyrmex and Atta ants. First, an overview of the relevant aspects of the biology and taxonomy of
leaf cutters and of their parasitoids is provided. Second, I show the peculiarities of the parasitoids attacking behaviors towards their
host as well as the responses or ant defenses against the phorids exhibited by their hosts. Third, I discuss relevant aspects of the
interactions between hosts and parasitoids. Finally, the review ends demonstrating why these phorids could be promising biological
control agents of leaf-cutter pests and suggests priority lines of research for the future.

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Elizalde, L. y Folgarait, P. J. 

Journal of Insects Science 12:1-26 – 2012

Abstract: Host-searching and oviposition behaviors of parasitoids, and defensive responses of the hosts, are fundamental in shaping the ecology of host-parasitoid interactions. In order to uncover key behavioral features for the little known interactions between phorid parasitoids (Diptera: Phoridae) and their leaf-cutting ant hosts (Formicidae: Attini), host-related behavioral strategies (i.e., host searching and oviposition) for 13 phorid species, and host defensive responses (i.e., hitchhikers and particular body postures) for 11 ant species, were studied. Data was collected at 14 localities, one of them characterized by its high species richness for this host-parasitoid system. Phorid species showed both great variation and specificity in attacking behaviors. Some chose their hosts using either an ambush or an actively searching strategy, while some species attacked ants on different body parts, and specialized on ants performing different tasks, such as when ants were foraging, removing wastes to refuse piles, or repairing the nest. Combining all the behaviors recorded, most phorid species differed in performance in at least one, making it possible to recognize species in the field through their behavior. Phorid species that attacked hosts with greater activity levels showed overall higher attack rates, although there was no significant correlation between attack rates by most phorid species and ant activity outside the nest while parasitoids were attacking. The presence of phorids was a significant determinant for the presence of defensive behaviors by the ants. Although ant species varied in the incidence levels of these defensive behaviors, most ant species reacted against different phorids by utilizing similar behaviors, in contrast to what parasitoids do. General features of the observed phorid-ant interactions were parasitoid specialization and corresponding high interspecific variation in their behaviors, while their hosts showed generalized responses to attacks with high intraspecific variation. Behavioral patterns as well as specific features of these ant-parasitoid interactions are described, and their ecological importance discussed.

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Elizalde, L. y Folgarait, P. J.

Journal of Natural History 45: 2701-2723. – 2011

Abstract: Little is known about the natural history of phorid parasitoids of leaf-cutting ants, an important pest in the Neotropics. This is particularly so for phorids attacking Acromyrmex species. We searched for phorids ovipositing and reared them from ants collected in the field. We found that these phorids formed a guild. Acromyrmex phorids selected ants from all sizes available outside the nests, whereas Atta phorids did not parasitize the smallest workers and soldiers. Maximum parasitism by phorids was 12% for Acromyrmex and 35% for Atta hosts, percentages higher than any reported previously. Some phorid species coexisting in a site showed differences in developmental times. Only 1.1% of phorids collected over hosts were males; however, as the male : female ratios from parasitoid rearing did not differ from one, mating is suspected to occur elsewhere. Our results helped to increase the knowledge of the phorids of leaf-cutters, and highlighted their potential use for the biocontrol of these ants.

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Folgarait, P. J.; Gorosito, N. Poulsen, M. Currie, C.

Current Microbiology 63: 250-258. – 2011

Abstract: Leaf-cutting ants are one of the main herbivores of the Neotropics, where they represent an important agricultural pest. These ants are particularly difficult to control because of the complex network of microbial symbionts. Leaf-cutting ants have traditionally been controlled through pesticide application, but there is a need for alternative, more environmentally friendly, control methods such as biological control. Potential promising biocontrol candidates include the microfungi Escovopsis spp. (anamorphic Hypocreales), which are specialized pathogens of the fungi the ants cultivate for food. These pathogens are suppressed through ant behaviors and ant-associated antibiotic-producing Actinobacteria. In order to be an effective biocontrol agent, Escovopsis has to overcome these defenses. Here, we evaluate, using microbial in vitro assays, whether defenses in the ant-cultivated fungus strain (Leucoagaricus sp.) and Actinobacteria from the ant pest Acromyrmex lundii have the potential to limit the use of Escovopsis in biocontrol. We also explore, for the first time, possible synergistic biocontrol between Escovopsis and the entomopathogenic fungus Lecanicillium lecanii. All strains of Escovopsis proved to overgrow A.lundii cultivar in less than 7 days, with the Escovopsis strain isolated from a different leaf-cutting ant species being the most efficient. Escovopsis challenged with a Streptomyces strain isolated from A. lundii did not exhibit significant growth inhibition. Both results are encouraging for the use of Escovopsis as a biocontrol agent. Although we found that L. lecanii can suppress the growth of the cultivar, it also had a negative impact on Escovopsis, making the success of simultaneous use of these two fungi for biocontrol of A. lundii questionable.

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Guillade, A. y Folgarait, P. J.

Journal of Economic Entomology 104: 32-40. – 2011

Abstract: Leaf-cutting ants in the genus Atta F. (Formicidae, Attini) are among the most important pest arthropods in Central and South America, consuming more vegetation than any other animal group. Among the organisms attacking ants in nature, flies of the family Phoridae have been proposed as the most promising biocontrol agents for pest ants. Four phorid species, Apocephalus setitarsus Brown, Myrmosicarius brandaoi Disney, Myrmosicarius gonzalezae Disney, and Eibesfeldtphora trilobata Disney, were reared from ants collected at Atta vollenweideri Forel nests and off foraging trails in Santa Fe province in Argentina. E. trilobata attacked larger ants and had bigger adults than the other species, also exhibiting the longest developmental time. Correlations between size of hosts and size of adults, as well as between size of adults and developmental times, could be established only in some cases. No differences were found between the sizes of the hosts from which males and females emerged. The natural percentage of parasitism varied throughout the seasons and seemed to be influenced by the extreme drought affecting the study site. We discuss why all four species would be suitable candidates for integrating an assemblage of biocontrol agents against A. vollenweideri.

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Folgarait, P.J., Marfetán, J. A. y Cafaro, M.

Environmental Entomology 40: 342-349 – 2011

Abstract: Leaf-cutter ants (Acromyrmex and Atta spp.) exhibit ancient and complex interactions with the symbiotic fungus Leucoagaricus (Basidiomycetes: Agaricales) from which they feed, and with the virulent and specific fungus Escovopsis weberi J.J. Muchovej & Della Lucia (Ascomycetes: Hypocreales) that attacks the ants’ fungal gardens. This system offers a unique opportunity to study possible avenues for replacing polluting pesticides with a biological control agent against the ants. We isolated both Leucoagaricus sp. and E. weberi from the gardens of Acromyrmex lundii Guérin-Méneville colonies and confronted them with each other by growing Leucoagaricus on petri dishes and placing inoculated pieces of agar inoculated with E. weberi at the edges. Here we present growth curves of Leucoagaricus sp. and E. weberi in the absence of each other, as a baseline to which we compare the effect of the fungi on each other. As expected, we found a negative effect of E. weberi on the ant cultivar from different colonies of A. lundii. E. weberi increased its growth rate, as well as the levels of conidiation, in the presence of the ant cultivar. We determined that a soluble and diffusible compound, released by the cultivar, triggered, was responsible for, or did both for the increased levels of conidiation in E. weberi, and that this response was reversible. We discuss why our results are encouraging from a biological control perspective.

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Elizalde, L. y Folgarait, P. J.

Journal of Biogeography 37: 2305- 2316. – 2010

Abstract:

• Aim Because of the obligatory relationship between endoparasitoids and their hosts, we presume that hosts exert strong selection pressure on parasitoids. One prediction is a positive relationship between host diversity and parasitoid richness. This relationship could be the product of resource availability which could lead to more opportunities for speciation, or could represent shared responses to the environment by both groups.
• Location Argentina and Paraguay.
• Methods We sampled a 1800-km transect to test for a correlation between the richness of leaf-cutting ant hosts and their phorid parasitoids. Regression models were used to assess if host and environmental variables could explain phorid species richness at nest, hectare and locality spatial scales. We used canonical correspondence analysis (CCA) to explore if there were similar responses of phorid species to particular host and environmental variables at different spatial scales, and partial CCA to separate the relative importance of both groups of variables.
• Results Phorid richness was positively correlated with host richness. Host richness/abundance accounted for 20–53% of the variation in parasitoid richness at the hectare and locality scales of analysis, with most of the variation accounted for by ant abundance. We were not able to assess the prediction at the nest scale as only one phorid species was found at most nests. Climatic variables did not explain phorid species richness once host variables were in the models. Partial CCA showed that host-related variables accounted for most of the variance associated with phorid species ordination at the nest and hectare scales, but not at the largest grain, the locality, where climatic variables were more important. However, most phorid species did not show particular positions along the climatic gradient.
• Main conclusions The association between parasitoid richness and host richness and abundance, and the overall weak associations with environmental variables, suggest that these host variables are key factors influencing parasitoid speciation.

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Brown, B., Disney, H., Elizalde, L. and Folgarait, P.J.

Sociobiology55 (1B): 165-190 – 2010

Abstract: The following new species of Apocephalus ant-parasitizing flies are described: Apocephalus exlobicornis Brown & Disney, A. exstriatus Brown & Disney, A. flavitenuipes Brown & Disney, A. intermedius Brown & Disney, A. longisetarum Brown & Disney, A. necdivergens Brown & Disney, A. noetingerorum Brown & Disney, A. penicillatus Brown & Disney, and A. philhispidus Brown & Disney. Host records are reported for each species, as well as new host records for the previously described A. mucronatus Borgmeier, A. neivai Borgmeier, A. setitarsus Brown, A. velutinus Borgmeier, A. viscosae Disney, and for one further unnamed species.

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Disney, H. L., Elizalde, L. & Folgarait, P. J.

Sociobiology 54: 601-632. – 2009

Abstract: The subgenus Eibesfeldtphora, of the genus Neodohrniphora, is raised to the rank of genus. Cremersia is synonymised with Neodohrniphora and N. zikani is restored to its original status as a species. New keys to the known males of Myrmosicarius and to all the females of Neodohrniphora are provided. The following new species from Argentina are described, Dacnophora cumatta Disney, Eibesfeldtphora cumsaltensis Disney and E. trilobata Disney, Neodohrniphora setifemur Disney from Ecuador, N. unichaeta Disney from Argentina and Pseudacteon confusus Disney from Ecuador.

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Disney, R. H., Elizalde, L.y Folgarait, P. J.

Sociobiology 51: 95-117. – 2008

Abstract: Lucianaphora folgaraitae Disney n. gen., n. sp., Macrocerides attophilus n. sp. are described, both being collected over leaf-cutter ants and Cremersia crassicostalis n. sp. from females collected over army ants. Some species collected with army ants are given code letters until they are linked up with their unknown sex. Host records for previously known species were all from colonies of army ants, whose myrmecophiles are better documented than those recorded from the colonies of leaf-cutter ants.

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Disney, R. L. H.; Elizalde, L.; Folgarait, P. J.

Sociobiology 47: 771-809 – 2006

Abstract: The genus Myrmosicarius Borgmeier is revised. M. brandaoi n. sp., M. cristobalensis n. sp., M. gonzalezae n. sp. and M. longipapis n. sp. from Argentina, with M. cristobalensis from Paraguay also, are described. M. diabolicus is synonymized with M. crudelis and M. cuspidatus is synonymized with M. catharinensis. A new key to the females is provided and new host records reported.

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Folgarait, P. J., O. Bruzzone y L. Gilbert.

Biological Control 28: 368-378 – 2003

Abstract: We monitored weekly relative abundances of adult female Pseudacteon (Diptera: Phoridae) species between February 1998 and May 2000 in Argentina. Fire ant-phorids were active around mounds of Solenopsis richteri Forel throughout the year. Phorid species richness ranged from six species during the summer-fall, to a single, large species during the winter. Species were classified as winter, summer, or fall-spring species, depending on times of peak mean abundance. We used descriptive multivariate techniques to analyze phorid phenological data (correspondence analysis), climatic data (principal component analysis), and their relationships (canonical correspondence analysis=CCA) at three temporal scales. The long-term mean temperatures, the mean and minimum sampling-time temperature, and the cumulative number of days without rain from the two months preceding each sampling day explained >90% of the variance when the data for sampling dates were averaged across the same months over the two years. Pseudacteon borgmeieri Schmitz, the winter dominant, was associated with lower temperatures and rainfall, whereas Pseudacteon curvatus Borgmeier, the summer dominant, showed the opposite pattern. Among the fall-spring species, Pseudacteon comatus Borgmeier was associated with months of higher maximum temperatures, longer photoperiods, and lower relative humidity. Pseudacteon nudicornis Borgmeier, in contrast, showed the opposite pattern. Pseudacteon tricuspis Borgmeier, was associated with months, typically in fall, having greater rainfall and fewer days with frosts. Implications of these patterns for the process of selecting particular species of S. richteri-attacking Pseudacteon for use in biological control introductions against imported fire ants are discussed in relation to climates of source and release areas.

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Folgarait, P.J., L. A. Dyer, R. Marquis, y H. E. Braker

Entomologia Experimentalis et Applicata 80: 521-530.  –  1996

Abstract: To examine the susceptibility of five Costa Rican tree species to leaf-cutter ants (Atta cephalotes L.: Formicidae, Attini), young and mature leaves from trees that were grown in a plantation under full sun and partial shade were offered to six leaf-cutter colonies located in full sun and six in partial shade. In addition to offering leaf disks to the ants, we offered large pieces of leaves to assess the effect of cutting leaves on food choices. Leaf-cutters responded differently to each plant species, preferring Virola koschyni Warburg (Myristicaceae) and Hyeronima alchorneoides Allemao (Euphorbiaceae) over Stryphnodendrum microstachyum Poeppig & Endlicher (Mimosoideae), Pentaclethra macroloba Willdenow (Fabaceae) and Vochysia ferruginea Martius (Vochysiaceae). In agreement with previous studies, interspecific differences among the tree species in water and saponin content appeared to account for the observed ant preferences among the five tree species: leaf-cutter ants preferred leaves and disks with more water and less saponins and the five tree species varied significantly in these traits. An observed positive correlation between preference and phenolic/nitrogen ratio appears to be spurious, and is instead due to a negative correlation between water content and nitrogen content. For the first time, Atta nest location has been shown to affect consumption: nests located in partial shade removed more leaf material than those from the sun plots. However, nest location had no effect on preference ranking of the tree species tested. Pieces of leaves from all the tree species grown in partial shade were significantly more removed than those trees grown in full sun. Leaf age, toughness, leaf specific weights, ant activity, and colony were not correlated with food choices. Because of the observed preferences, the five tree species should not be considered as equal candidates for plantation purposes. However, complete characterization of the candidate status of tree species for plantations in the neotropics must include information on the ability of such species to tolerate pest attacks in addition to their natural defenses to attack.

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Folgarait, P.J., A. Farji Brener y J. Protomastro

Ecología Austral 4:11-17. –  1994

Abstract: The diet of the leaf-cutter ant Acromyrmex striatus was used as indirect evidence for potential antiherbivore activity by the nectivorous ant Camponotus blandus and by chemical and mechanical plant defenses. Data on ant activity, plant abundance, and foliar material for analyses of chemical and mechanical plant defenses were collected during spring in a subtropical forest in the Argentinean Chaco. We found a negative relationship between the proportion of visits by C. blandus and leaf harvesting of A. striatus for the plant species that offer nectar. However, the most abundant plant species in the forest comprised the greatest part of the leaf-cutter diet. In general, no relationship was found between chemical or mechanical defenses and leaf-cutter diet for all the plant species of the forest. A few plant species with high levels of plant defenses suffered little or no harvesting by leaf-cutter ants. Our findings suggest two main reasons for the absence or low representation of nectar-offering plant species in the diet of A. striatus: nectivorous ant activity and low plant species abundances.

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 A. Farji Brener, Folgarait, P.J., y J. Protomastro

Revista de Biología Tropical 40: 341-344. – 1992

Abstract: The hypothesis that the nectivore ant Campollotus blandus operates as an altemative defense of the shrub Capparis retusa against the leaf-cutting ant Acromyrmex striatus was tested. Data were obtained in a forest reserve of the Argentinean subtropical dry Chaco (250 55′ S, 62005′ W) during the spring of 1986. C. refusa is abundant, but it is not a pan of the leaf-cutting ant diet « 1 %), has a high proportion of nectivore ant visits. and low levels of chemical and physicaldefenses. Shrubs without C. blalldus were intensively harvested by A. striatus, whích suggests that the nectivore ant is an altemative defense for the shrub against the leafccutting ant.

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