Control of phytonematodes is very hard and requires a combination of techniques to succeed. Alternative control through plant extracts may result in the discovery of nematicide substances. Research aimed at evaluating the effect of 33 plants submitted to aqueous extraction against Panagrellus redivivus in vitro. Concentrations were prepared at 1.25, 2.5, 5, 10, and 20%. Monitoring happened at 0, 6, 12, 24 and 30 hours after preparation. Counting considered dead nematodes subtracted from alive ones. Juveniles were also counted, and extract efficiency was expressed in percentage of control or stimuli. Data were submitted to variance analysis. Significant results got with the Scott-Knott test (5%), and multiple linear regression analysis. Extracts were observed acting as controllers, but also as stimulators to nematode reproduction. The best controlling performance was set by Carica papaya (-66% at 20%; -33.7% at 10%), Euphorbia milii (-37% at 20%), Psychotria carthagenensis (-25.5% at 2.5%), Clusia variegate (-22% at 20%), and Zamioculcas zamiifolia (-21.5% at 20%). Stimulator extracts were Mentha villosa at 10% (+148%) and 2.5% (+131.5%), followed by Aloe vera (+123% at 5%), Schinus molle (+112.5% at 10%), Schefflera arboricola (+93.5% at 5%), C. variegate (+89% at 5%), and S. molle (+88% at 5%). Some extracts kept population stable throughout the experiment, presenting lower control indexes. Besides an additive effect, there was an individual influence of concentration or time on control.

Acromyrmex leaf-cutting ants use the antibiotics produced by ectosymbionts (Actinobacteria) to suppress the growth of Escovopsis spp., which are the specialized parasites of attine fungus gardens. However, the spectrum of activity of these bacteria and their interactions with insect immune systems have not been thoroughly studied. The objective of this study was to evaluate whether the presence of symbiotic actinobacteria covering the entire cuticle of Acromyrmex subterraneus subterraneus (Forel) (Hymenoptera: Formicidae) workers provides protection against two fungus species, Metarhizium anisopliae (Metschn.) Sorokin (Hypocreales), a persistent entomopathogenic, and Aspergillus ochraceus G. Wilh. (Eurotiales), an opportunistic insect pathogen. We assessed the mortality rates of three groups of Ac. subterraneus subterraneus workers inoculated with a suspension of one of the two pathogens: external workers (EXT), internal workers with actinomycetes covering the whole body (INB), and internal workers without actinomycetes covering the whole body (INØ). We also assessed the encapsulation response, which is a parameter of innate immunity, to determine whether the pathogens affect immune responses in the ant. All bioassays were conducted on workers from seven laboratory colonies of Ac. subterraneus subterraneus. Mortality tests showed that actinomycetes do protect the workers of group INB against M. anisopliae, but not against A. ochraceus. Regarding the encapsulation response, INB ants treated with A. ochraceus conidia exhibited immunosuppression due to this pathogen. All three groups of workers that received M. anisopliae conidia presented some degree of immunosuppression after pathogen exposure. These results indicate that workers without visible bacteria cover, specially the external workers (EXT), are more resistant to entomopathogenic fungi. Nevertheless, bacterial actinomycetes present in young workers are important in protecting them from ubiquitous entomopathogenic fungi.

No abstract

O conhecimento dos efeitos de fenômenos climáticos extremos, como as geadas em diversas culturas é de grande importância para o zoneamento climático visando à otimização dos resultados de produção. As fontes de energias alternativas e a utilização de biodisel vêm abrindo um mercado promissor para as culturas energéticas como Pinhão manso, Girassol, Eucalipto e outras, portanto se faz necessário estabelecer relações entre as culturas e os efeitos fisiológicos que as geadas podem causar a estas. Deste modo, o presente trabalho objetiva trazer informações técnico-científicas sobre o assunto, levando em consideração a falta de estudos nesta área.

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