No abstract

Alternative methods of pest control can and should be encouraged, especially those that consider the reality of smallholder family farmers. Here, we evaluated the potential of Agave americana (agave) extracts for the control of the aphid Brevicoryne brassicae in cabbage (Brassica oleracea L. var acephala) in the field and laboratory. The field experiments consisted of the evaluation of the proportion of dead aphids on cabbage plants after application of agave extracts. In the field, agave mixed with cow milk caused mortality above 80% and was the most effective extract. Agave mixed with water and agave mixed with ethanol elicited mortality above 60%. In the laboratory, we evaluated the mortality of aphids after the application of different concentrations of aqueous agave extracts; the commercial insecticide deltamethrin was included as positive control. Evaluation took place at 3, 6, 12, 24, 48 and 72 hr after applying the treatment. As expected, deltamethrin was the most effective treatment. However, agave extract at concentrations of 0.750 and 0.500 g/mL caused >70% mortality 3 hr after application. We conclude that A. americana extracts decreased aphid populations and is a promising alternative to the commercial insecticide against aphids in cabbage. K E Y W O R D S agave, aphids, biopesticides, horticulture, plant extracts

O objetivo do trabalho foi avaliar o efeito dos extratos aquosos de hortelã e melissa na germinação e vigor de sementes de tanchagem. O experimento foi conduzido no Departamento de Fitotecnia da Universidade Federal de Viçosa, no mês de abril de 2011. O delineamento utilizado foi o inteiramente casualizado com cinco tratamentos (testemunha, 25%, 50%, 75% e 100 % do extrato aquoso de hortelã e melissa) e quatro repetições. Os extratos foram preparados utilizando a parte aérea das plantas, na proporção de 100g de planta para 1 L de água destilada. Foram utilizadas 50 sementes de tanchagem em cada caixa gerbox, previamente umedecido com os extratos aquosos (correspondentes aos tratamentos), estas foram levadas para germinar em câmara de germinação, em temperatura de 20°C, fotoperíodo de 16 horas luz e 8 horas escuro, por 14 dias. Durante esse tempo foram feitas às contagens diárias das sementes germinadas para calcular o índice de velocidade de germinação e ao final dos 14 dias foi calculada a porcentagem de germinação. Sementes de tanchagem não submetidas aos extratos aquosos de melissa e hortelã apresentaram-se mais vigorosas quando comparado com as concentrações, evidenciando o potencial alelopático de melissa e hortelã sobre a sua qualidade fisiológica.

We investigated the effects of Fe-mining tailings of the Fundão dam on water quality, concerning physical and chemical parameters, aiming to infer the recovery process of the affected areas, and prospects of water quality in the coming years. Water quality data from the Gualaxo do Norte and Carmo rivers were evaluated in three moments: (i) before the dam rupture (1999–2000); (ii) one year after the rupture of the Fundão dam (2016); and (iii) after the implementation of recover mitigation activities (2017–2019). Concerning the variables evaluated, the mean concentrations of Fe and Mn were higher in the dry period, and increasing turbidity was detected in the rainy season. The turbidity, even after the recovery measures, peaked at 300 and 400 NTU in 2017 and 2019, respectively. The concentrations of dissolved Fe, Mn and Cr, closely related to the tailings, decreased with rainfall by a dilution mechanism. Conversely, the concentrations of Cd, Al, Zn, and Cu increased in the rainy season, probably by greater erosion. The implementation of the recovery actions at the Gualaxo do Norte headwaters are helping to reduce the Mn and Fe concentrations and turbidity downriver, all associated with the Fe-mining tailings.

Resumo: A construção do conhecimento tradicional na agricultura ocorreu a partir de relações sociais baseadas no intercâmbio de conhecimento, na troca de sementes e no desenvolvimento de relações tecnológicas mais