Alcides Moino Junior

Stimulation of the Salicylic Acid Pathway Aboveground Recruits Entomopathogenic Nematodes Belowground

Plant defense pathways play a critical role in mediating tritrophic interactions between plants, herbivores, and natural enemies. While the impact of plant defense pathway stimulation on natural enemies has been extensively explored aboveground, belowground ramifications of plant defense pathway stimulation are equally important in regulating subterranean pests and still require more attention. Here we investigate the effect of aboveground stimulation of the salicylic acid pathway through foliar application of the elicitor methyl salicylate on belowground recruitment of the entomopathogenic nematode, Steinernema diaprepesi. Also, we implicate a specific root-derived volatile that attracts S. diaprepesi belowground following aboveground plant stimulation by an elicitor. In four-choice olfactometer assays, citrus plants treated with foliar applications of methyl salicylate recruited S. diaprepesi in the absence of weevil feeding as compared with negative controls. Additionally, analysis of root volatile profiles of citrus plants receiving foliar application of methyl salicylate revealed production of d-limonene, which was absent in negative controls. The entomopathogenic nematode S. diaprepesi was recruited to d-limonene in two-choice olfactometer trials. These results reinforce the critical role of plant defense pathways in mediating tritrophic interactions, suggest a broad role for plant defense pathway signaling belowground, and hint at sophisticated plant responses to pest complexes.

Evaluation of entomopathogenic nematodes under laboratory and greenhouses conditions for the control of Spodoptera frugiperda

The increased corn planting grown in the late season crop and the use of a notillage planting system benefits the development of Spodoptera frugiperda, the main pest of corn crop. Thus, this study aimed to select entomopathogenic nematodes based on the mortality of S. frugiperda, and to adjust the nematode concentrations in the laboratory and evaluate the action of these organisms in greenhouse conditions. Seventeen nematode populations were tested at concentrations of 100, 250, and 500 infective juveniles (IJ)/larvae. The obtained data were submitted to the polynomial regression test. In the greenhouse, corn sowing was performed in plastic buckets with soil, corn straw, and water. After 7 days, Steinernema arenarium or Heterorhabditis sp. RSC02, and the larvae were added (40 larvae, one larvae/repetition). The data were submitted to the variance analysis and the Scott-Knott test (P<0.05). In the laboratory, tests with S. arenarium and Heterorhabditis sp. RSC02 caused mortality of 85 and 90%, respectively, being selected for the concentrations test. Concentrations of 150, 200, 250, 300, and 350IJ larvae-1 were tested. At a concentration of 200IJ larvae-1, S. arenarium and Heterorhabditis sp. RSC02 caused 100 and 97.6% mortality in laboratory, respectively, and in the greenhouse caused 77.5 and 87.5% mortality, respectively, when compared to the control (7.5%).

Virulence of entomopathogenic nematodes (Rhabditida: Steinernematidae and Heterorhabditidae) for the control of Diabrotica speciosa germar (coleoptera: chrysomelidae)

Os nematoides entomopatogenicos sao utilizados no controle biologico de pragas de solo, e sao promissores para o controle de D. speciosa. Neste trabalho, objetivou-se avaliar o potencial de especies nativas e exoticas de isolados de nematoides entomopatogenicos para o controle de D. speciosa, em condicoes de laboratorio e de casa de vegetacao. Verificou-se que todos os nematoides causaram mortalidade larval. Os mais virulentos foram Heterorhabditis sp. RSC01 (94%), Steinernema glaseri (84%), Heterorhabditis sp. JPM04 (82%) e Heterorhabditis amazonensis RSC05 (78%). Nao houve efeito dos isolados Heterorhabditis sp. RSC01 e S. glaseri em ovos. A mortalidade maxima de larvas de D. speciosa por Heterorhabditis sp. RSC01 foi observada na concentracao de 300 JI / inseto, enquanto para S. glaseri a maior mortalidade foi obervada na concentracao de 200 JI/ inseto. O isolado Heterorhabditis sp. RSC01 causou mais de 80% de mortalidade de pupas na concentracao de 250 IJ/ inseto. A virulencia de Heterorhabditis sp. RSC01 e S. glaseri foi afetada pela temperatura. O isolado Heterorhabditis sp. RSC01 causou reducao na sobrevivencia da larvas em casa de vegetacao em todas as concentracoes de juvenis infectantes testadas e nao houve diferenca na mortalidade entre os diferentes tratamentos.

Eliciting maize defense pathways aboveground attracts belowground biocontrol agents

Plant defense pathways mediate multitrophic interactions above and belowground. Understanding the effects of these pathways on pests and natural enemies above and belowground holds great potential for designing effective control strategies. Here we investigate the effects of aboveground stimulation of plant defense pathways on the interactions between corn, the aboveground herbivore adult Diabrotica speciosa, the belowground herbivore larval D. speciosa, and the subterranean ento-mopathogenic nematode natural enemy Heterorhabditis amazonensis. We show that adult D. speciosa recruit to aboveground herbivory and methyl salicylate treatment, that larval D. speciosa are relatively indiscriminate, and that H. amazonensis en-tomopathogenic nematodes recruit to corn fed upon by adult D. speciosa. These results suggest that entomopathogenicnematodes belowground can be highly attuned to changes in the aboveground parts of plants and that biological control can be enhanced with induced plant defense in this and similar systems.

Efeito de extratos vegetais aquosos sobre a mosca-das-frutas Ceratitis capitata (Wiedemann) (Diptera: Tephritidae)

O objetivo deste trabalho foi avaliar o efeito de extratos vegetais para o controle de Ceratitis capitata. Os tratamentos foram extratos aquosos preparados com vegetais frescos e secos na proporcao de 20% p/v (peso do vegetal/volume de agua) da folha, do ramo e do fruto de cinamomo, da folha de arruda, do alho e do gengibre. Para a avaliacao sobre a fase imatura, cada repeticao foi constituida de uma placa com 20 larvas ou 20 pupas, as quais foram imersas em 1 mL de extrato durante 30 segundos. Para o extrato preparado com os frutos secos de cinamomo, foram avaliadas as concentracoes de 0, 5, 10, 15, 10 e 25% p/v. As avaliacoes foram realizadas apos cinco dias, contando-se o numero de larvas mortas, de pupas inviaveis e de adultos deformados. Para a fase adulta, foram avaliados apenas os extratos preparados com vegetais secos. Cada repeticao foi constituida de um pote plastico contendo um fruto de ameixa vermelha e um rolete de algodao embebido com 5 mL de extrato. Foram transferidas tres femeas e dois machos de C. capitata para cada pote plastico. Apos dois dias, realizou-se a avaliacao da mortalidade de adultos e a retirada dos frutos, os quais foram individualizados, e apos sete dias contou-se o numero de larvas desenvolvidas. Verificou-se que todos os extratos reduziram o numero de insetos viaveis, com destaque para o de cinamomo, o qual teve efeito tambem sobre a fase adulta. Nas condicoes estudadas, nenhum extrato teve resultado sobre a fecundidade das femeas de C. capitata.

Parameters affecting plant defense pathway mediated recruitment of entomopathogenic nematodes

ABSTRACT Entomopathogenic nematodes are natural enemies and effective biological control agents of subterranean insect herbivores. Interactions between herbivores, plants, and entomopathogenic nematodes are mediated by plant defense pathways. These pathways can induce release of volatiles and recruit entomopathogenic nematodes. Stimulation of these plant defense pathways for induced defense against belowground herbivory may enhance biological control in the field. Knowledge of the factors affecting entomopathogenic nematode behaviour belowground is needed to effectively implement such strategies. To that end, we explore the effect of elicitor, elicitor dose, mechanical damage, and entomopathogenic nematode release distance on recruitment of entomopathogenic nematode infective juveniles to corn seedlings. Increasing doses of methyl jasmonate and methyl salicylate elicitors recruited more entomopathogenic nematodes as did mechanical damage. Recruitment of entomopathogenic nematodes was higher at greater release distances. These results suggest entomopathogenic nematodes are highly tuned to plant status and present a strategy for enhancing biological control using elicitor-stimulated recruitment of entomopathogenic nematodes.

Deslocamento vertical de nematóides entomopatogênicos (Rhabditida: Heterorhabditidae) na busca por Dysmicoccus texensis (Tinsley) (Hemiptera: Pseudococcidae) em laboratório e casa-de-vegetação

Varios fatores devem ser considerados na avaliacao da eficiencia de um entomopatogeno no controle de um inseto-praga. Com relacao aos nematoides entomopatogenicos, alem da patogenicidade e virulencia, e importante conhecer a capacidade de busca, pois quanto maior sua eficiencia, maior a chance de encontro com o hospedeiro. Assim, neste trabalho, objetivou-se avaliar o deslocamento vertical de nematoides entomopatogenicos (Heterorhabditis), visando ao controle da cochonilha-da-raiz-do-cafeeiro Dysmicoccus texensis (Tinsley). Para avaliacao em laboratorio, foi feito teste em coluna de areia de 5 cm (em delineamento inteiramente casualizado) onde os isolados CCA e JPM3 foram aplicados em suspensao aquosa no topo da coluna em tres concentracoes (50, 100 e 500 JIs/inseto), com avaliacao da mortalidade apos 5 dias. No experimento de coluna de solo, foi usada uma coluna de 25 cm, composta por cinco extratos de 5 cm. Foram utilizados dois isolados (CCA e JPM3) e dois metodos de aplicacao: cadaver infectado e suspensao aquosa, ambos avaliados nas diferentes profundidades. O experimento foi conduzido num delineamento fatorial 3x2x5, em condicoes de casa-de-vegetacao. No experimento de coluna de areia, nao houve diferenca entre os isolados avaliados e ambos alcancaram valor de 92% de mortalidade. No experimento de deslocamento em coluna de solo, observou-se que JPM3 foi mais eficiente que CCA, nos dois metodos de aplicacao avaliados. Quanto aos metodos de aplicacao, o de suspensao aquosa apresentou melhores resultados para os dois isolados, e JPM3 aplicado em suspensao aquosa, foi o melhor tratamento em quase todas as profundidades avaliadas.

Host-seeking behavior of the Heterorhabditis amazonensis nematode in response to stimulant sources1

Plants and insects have coexisted for approximately 350 million years and have developed elaborate systems that highlight the tritrophic interplay among plants, insect herbivores and their natural enemies. Just as plants can attract predators and parasitoids, including natural enemies, they can also interact with pathogens (Elliot et al. 2000). The ability to attract natural enemies is referred to ABSTRACT RESUMO