Entomopathogenic nematology in Latin America: A brief history, current research and future prospects

Since the 1980s, research into entomopathogenic nematodes (EPNs) in Latin America has produced many remarkable discoveries. In fact, 16 out of the 117 recognized species of EPNs have been recovered and described in the subcontinent, with many more endemic species and/or strains remaining to be discovered and identified. In addition, from an applied perspective, numerous technological innovations have been accomplished in relation to their implementation in biocontrol. EPNs have been evaluated against over 170 species of agricultural and urban insects, mites, and plant-parasitic nematodes under laboratory and field conditions. While much success has been recorded, many accomplishments remain obscure, due to their publication in non-English journals, thesis dissertations, conference proceedings, and other non-readily available sources. The present review provides a brief history of EPNs in Latin America, including current findings and future perspectives.Fil: San Blas, Ernesto. Instituto Venezolano de Investigaciones Científicas; VenezuelaFil: Campos Herrera, Raquel. Consejo Superior de Investigaciones Científicas; EspañaFil: Dolinski, Claudia. Universidade Estadual Do Norte Fluminense Darcy Ribeiro; BrasilFil: Monteiro, Caio. Universidade Federal de Goiás; BrasilFil: Andaló, Vanessa. Universidade Federal de Uberlandia; BrasilFil: Leite, Luis Garrigós. Universidade Estadual de Campinas; BrasilFil: Rodríguez, Mayra G.. Centro Nacional de Sanidad Agropecuaria; CubaFil: Morales Montero, Patricia. Instituto Venezolano de Investigaciones Científicas; VenezuelaFil: Sáenz Aponte, Adriana. Pontificia Universidad Javeriana; ColombiaFil: Cedano, Carolina. Universidad Nacional de Trujillo; PerúFil: López Nuñez, Juan Carlos. Centro Nacional de Investigaciones del Café; ColombiaFil: del Valle, Eleodoro Eduardo. Universidad Nacional del Litoral; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Doucet, Marcelo Edmundo. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Zoología Aplicada; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Diversidad y Ecología Animal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto de Diversidad y Ecología Animal; ArgentinaFil: Lax, Paola. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Zoología Aplicada; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Diversidad y Ecología Animal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto de Diversidad y Ecología Animal; ArgentinaFil: Navarro, Patricia D.. Instituto de Investigaciones Agropecuarias; ChileFil: Báez, Francisco. Instituto Nacional Autonomo de Investigaciones Agropecuarias; EcuadorFil: Llumiquinga, Pablo. Instituto Nacional Autonomo de Investigaciones Agropecuarias; EcuadorFil: Ruiz Vega, Jaime. Instituto Politécnico Nacional ; MéxicoFil: Guerra Moreno, Abby. Laboratorio de Biotecnología; PanamáFil: Stock, S. Patricia. University of Arizona; Estados Unido

Study of some factors that affect the epizootic of Zoophthora radicans ano utilization of the fungus to control Empoasca sp.

Foram analisados e comparados os processos de germinação e habilidade de infecção dos isolados ARS-1590, ARS-1261 e ARS-1229 de Zoophthora radicans sobre ninfas do 5° instar de Empoasca kraemeri a 20°C e 100% de umidade relativa (UR). A germinação dos conídios primário dos isolados sobre o inseto iniciou-se dentro do período de 2 horas após a inoculação. A produção total de tubos germinativos tendeu a se igualar à de capiloconídios sobre o corpo do hospedeiro, 12 horas após a inoculação. A proporção de conídios secundários, dentro das formas geradas pelos conídios primários germinados sobre o inseto, não uItrapassou 25% em qualquer das regiões do corpo. A formação de apressório e penetração dos isolados iniciaram dentro do período de 6 horas após a inoculação. As penetrações dos isolados ocorreram em maior proporção no abdome seguido do tórax e cabeça do inseto tendo sido mais frequente nas membranas do corpo do que nos escleritos. Foram analisados e comparados os comportamentos dos três isolados sobre ninfas do 5° instar de E. kraemeri a 20ºC e 100% de UR. Os isolados ARS-1590 e ARS-1261 foram os mais indicados para o controle de Empoasca sp.. O isolado ARS-1590 apresentou menor DL50 (0,7 condídios por mm2) e menor tempo para iniciar a conídiogênese (9,1 horas) após a morte do inseto. O isolado ARS-1261 apresentou menores tempos médios de incubação para matar o inseto, variáveis de 65,0 a 75,0 horas, e maior produção de conídios (4,3 x 104 por inseto). Os tempos médios de incubação dos isolados para matar o inseto foram indiretamente proporcionais às doses de inoculação. Foi analisada a coni- diogênese do isolado ARS-1590 sobre diferentes instares do inseto a 20°C e 100% de UR, e sobre ninfas do 5º instar a diferentes temperaturas e 100% de UR. A produção de conídios foi diretamente proporcional à idade do hospedeiro. A faixa ótima de temperatura para o patógeno foi de 20 a 25°C, enquanto que a faixa de 15 a 20ºC foi favorável. Avaliou-se a estratégia da introdução inoculativa, pela aplicação de diferentes doses de micélio seco do fungo (isolado ARS-2282) em campo de feijão infestado com Empoasca sp.. A dose de 1 g/m2 do fungo foi a mais viável para a formação de focos primários da doença e indução da epizootia. O desenvolvimento epizoótico do fungo sobre a população do inseto foi dependente do período de orvalho e da densidade de cadáveres do inseto atacados pelo patógeno, sendo que, em condições subótimas de umidade o inóculo, foi dependente também da densidade populacional do hospedeiro. O fungo, aplicado na fase de crescimento vegetativo da cultura, reduziu a alta infestação da praga e possibilitou a recuperação das plantas.The germination and penetration hability of ARS-1590, ARS-1261 and ARS-1229 isolates of Zoophthora radicans on fifth instar Empoasca kraemeri nymphs, at 20°C and 100% relative humidity (RH), were investigated and compared. The primary conidia on the insect germinated within the 2 hr. after the inoculation, for all isolates. The secondary conidia proportion, among the forms produced by the primary conidia on the insect, did not exceed 25% in all body regions. The apressorium formation and isolate penetration began within the 6 hr. after inoculation. The penetration occured in greater proportion on the abdomen, followed by the thorax and head, more often through membrames than sclerites. The behaviour of the three isolates on fifth-instar E. kraemeri nymphs, at 20°C and 100% RH, were investigated and compared. The ARS-1590 and ARS-1229 isolates were the most indicated to Empoasca sp. control. The ARS- 1590 showed the lower LD50 (0,7 conidias per mm2), and lower time to start the esporulat.ion (9,1 hr.) after insect death. The ARS-1261 race showed the smaller mean incubation times, variable from 65,0 to 75,0 hr., and larger conidial production (4.3 x 104 per insect). The mean incubation times were indirectly related with the inoculation doses, for all isolates. Sporulation of the ARS-1590 isolate on leafhoppers of different ages, at 20°C and 100% RH, and on fifth-instar E. kraemeri, at different t.emperatures and 100% RH, were investigated. The conidial production was directly related with the leafhopper age. The optimal temperature to Z. radicans ranged from 20 to 25°C, although adequate sporulation also occurred from 15 to 20°C. The inoculative introduction strategy by application of different doses of dry micelia was investigated for the isolate ARS-2282 in a bean field infested with Empoasca sp. The most viable dose of the fungus was 1 g/m2 to attain a primary focus formation of the disease and epizootic induction. The epizootic on leafhopper populations was dependent upon the dew period and density of fungus-infected cadavers. At suboptimal conditions of humidity and inocule, the fungus was dependent on the host population density. Application of the fungus so as to coincide with the vegetative growing phase of the bean plants resulted in lower pest decreased infestation, allowing plant recovery

Study of some factors that affect the epizootic of Zoophthora radicans ano utilization of the fungus to control Empoasca sp.

Foram analisados e comparados os processos de germinação e habilidade de infecção dos isolados ARS-1590, ARS-1261 e ARS-1229 de Zoophthora radicans sobre ninfas do 5° instar de Empoasca kraemeri a 20°C e 100% de umidade relativa (UR). A germinação dos conídios primário dos isolados sobre o inseto iniciou-se dentro do período de 2 horas após a inoculação. A produção total de tubos germinativos tendeu a se igualar à de capiloconídios sobre o corpo do hospedeiro, 12 horas após a inoculação. A proporção de conídios secundários, dentro das formas geradas pelos conídios primários germinados sobre o inseto, não uItrapassou 25% em qualquer das regiões do corpo. A formação de apressório e penetração dos isolados iniciaram dentro do período de 6 horas após a inoculação. As penetrações dos isolados ocorreram em maior proporção no abdome seguido do tórax e cabeça do inseto tendo sido mais frequente nas membranas do corpo do que nos escleritos. Foram analisados e comparados os comportamentos dos três isolados sobre ninfas do 5° instar de E. kraemeri a 20ºC e 100% de UR. Os isolados ARS-1590 e ARS-1261 foram os mais indicados para o controle de Empoasca sp.. O isolado ARS-1590 apresentou menor DL50 (0,7 condídios por mm2) e menor tempo para iniciar a conídiogênese (9,1 horas) após a morte do inseto. O isolado ARS-1261 apresentou menores tempos médios de incubação para matar o inseto, variáveis de 65,0 a 75,0 horas, e maior produção de conídios (4,3 x 104 por inseto). Os tempos médios de incubação dos isolados para matar o inseto foram indiretamente proporcionais às doses de inoculação. Foi analisada a coni- diogênese do isolado ARS-1590 sobre diferentes instares do inseto a 20°C e 100% de UR, e sobre ninfas do 5º instar a diferentes temperaturas e 100% de UR. A produção de conídios foi diretamente proporcional à idade do hospedeiro. A faixa ótima de temperatura para o patógeno foi de 20 a 25°C, enquanto que a faixa de 15 a 20ºC foi favorável. Avaliou-se a estratégia da introdução inoculativa, pela aplicação de diferentes doses de micélio seco do fungo (isolado ARS-2282) em campo de feijão infestado com Empoasca sp.. A dose de 1 g/m2 do fungo foi a mais viável para a formação de focos primários da doença e indução da epizootia. O desenvolvimento epizoótico do fungo sobre a população do inseto foi dependente do período de orvalho e da densidade de cadáveres do inseto atacados pelo patógeno, sendo que, em condições subótimas de umidade o inóculo, foi dependente também da densidade populacional do hospedeiro. O fungo, aplicado na fase de crescimento vegetativo da cultura, reduziu a alta infestação da praga e possibilitou a recuperação das plantas.The germination and penetration hability of ARS-1590, ARS-1261 and ARS-1229 isolates of Zoophthora radicans on fifth instar Empoasca kraemeri nymphs, at 20°C and 100% relative humidity (RH), were investigated and compared. The primary conidia on the insect germinated within the 2 hr. after the inoculation, for all isolates. The secondary conidia proportion, among the forms produced by the primary conidia on the insect, did not exceed 25% in all body regions. The apressorium formation and isolate penetration began within the 6 hr. after inoculation. The penetration occured in greater proportion on the abdomen, followed by the thorax and head, more often through membrames than sclerites. The behaviour of the three isolates on fifth-instar E. kraemeri nymphs, at 20°C and 100% RH, were investigated and compared. The ARS-1590 and ARS-1229 isolates were the most indicated to Empoasca sp. control. The ARS- 1590 showed the lower LD50 (0,7 conidias per mm2), and lower time to start the esporulat.ion (9,1 hr.) after insect death. The ARS-1261 race showed the smaller mean incubation times, variable from 65,0 to 75,0 hr., and larger conidial production (4.3 x 104 per insect). The mean incubation times were indirectly related with the inoculation doses, for all isolates. Sporulation of the ARS-1590 isolate on leafhoppers of different ages, at 20°C and 100% RH, and on fifth-instar E. kraemeri, at different t.emperatures and 100% RH, were investigated. The conidial production was directly related with the leafhopper age. The optimal temperature to Z. radicans ranged from 20 to 25°C, although adequate sporulation also occurred from 15 to 20°C. The inoculative introduction strategy by application of different doses of dry micelia was investigated for the isolate ARS-2282 in a bean field infested with Empoasca sp. The most viable dose of the fungus was 1 g/m2 to attain a primary focus formation of the disease and epizootic induction. The epizootic on leafhopper populations was dependent upon the dew period and density of fungus-infected cadavers. At suboptimal conditions of humidity and inocule, the fungus was dependent on the host population density. Application of the fungus so as to coincide with the vegetative growing phase of the bean plants resulted in lower pest decreased infestation, allowing plant recovery

Entomopathogens Isolated from Invasive Ants and Tests of Their Pathogenicity

Some ant species cause severe ecological and health impact in urban areas. Many attempts have been tested to control such species, although they do not always succeed. Biological control is an alternative to chemical control and has gained great prominence in research, and fungi and nematodes are among the successful organisms controlling insects. This study aimed to clarify some questions regarding the biological control of ants. Invasive ant species in Brazil had their nests evaluated for the presence of entomopathogens. Isolated entomopathogens were later applied in colonies of Monomorium floricola under laboratory conditions to evaluate their effectiveness and the behavior of the ant colonies after treatment. The entomopathogenic nematodes Heterorhabditis sp. and Steinernema sp. and the fungi Beauveria bassiana, Metarhizium anisopliae, and Paecilomyces sp. were isolated from the invasive ant nests. M. floricola colonies treated with Steinernema sp. and Heterorhabditis sp. showed a higher mortality of workers than control. The fungus Beauveria bassiana caused higher mortality of M. floricola workers. However, no colony reduction or elimination was observed in any treatment. The defensive behaviors of ants, such as grooming behavior and colony budding, must be considered when using fungi and nematodes for biological control of ants

Inhibition of symbiote fungus of the leaf cutter ant Atta sexdens by secondary metabolites from the bacterium Xenorhabdus szentirmaii associated with entomopathogenic nematodes

ABSTRACT: Leaf-cutter ants (Hymenoptera: Formicidae) have evolved as dominant herbivores on the American continent. These social insects remove the leaves of economically important plant species to maintain their colony’s food reserves, the symbiotic fungus Leucocoprinus gongylophorus, a basidiomycete. Such fungus can be used for applications of fungicide molecules from metabolites generated by symbiont bacteria (Xenorhabdus and Photorhabdus) from entomopathogenic nematodes (Steinernema and Heterorhabditis). Through isolation and multiplication in tryptic soy broth (TSB) medium of the bacteria Xenorhabdus szentirmaii isolated PAM 25, we conducted laboratorial tests using treatments with 10, 25, and 50% of the metabolites obtained in the sixth day of cultivation. The treatments were centrifuged and filtered to generate a supernatant, which was diluted in potato + dextrose + agar (PDA), to verify the consequences of exposure to the fungus L. gongylophorus in Petri dishes. To confirm metabolite efficiency, the control treatments in PDA only and mixed (PDA+TSB) media were conducted simultaneously for 14 days. We observed total inhibition of the symbiont fungus in both the 25 and 50% dilutions during the first days of the tests. Our results support that these metabolites have inhibitory effect on the development of symbiont fungus of leaf-cutter ants

Entomopathogenic nematodes in agricultural areas in Brazil

Entomopathogenic nematodes (EPNs) (Steinernematidae and Heterorhabditidae) can control pests due to the mutualistic association with bacteria that kill the host by septicemia and make the environment favorable for EPNs development and reproduction. The diversity of EPNs in Brazilian soils requires further study. The identification of EPNs, adapted to environmental and climatic conditions of cultivated areas is important for sustainable pest suppression in integrated management programs in agricultural areas of Brazil. The objective was to identify EPNs isolated from agricultural soils with annual, fruit and forest crops in Brazil. Soil samples were collected and stored in 250 ml glass vials. The nematodes were isolated from these samples with live bait traps ([Galleria mellonella L. (Lepidoptera: Pyralidae) larvae]. Infective juveniles were collected with White traps and identified by DNA barcoding procedures by sequencing the D2/D3 expansion of the 28S rDNA region by PCR. EPNs identified in agricultural areas in Brazil were Heterorhabditis amazonensis, Metarhabditis rainai, Oscheios tipulae and Steinernema rarum. These species should be considered pest biocontrol agents in Brazilian agricultural areas