Universidade Federal de Viçosa

About: Universidade Federal de Viçosa is a education organization based out in Viçosa, Brazil. It is known for research contribution in the topics: Population & Dry matter. The organization has 16012 authors who have published 26711 publications receiving 353416 citations.

Influência de herbicidas e de sistemas de semeadura de Brachiaria brizantha consorciada com milho

Abstract: The aim of this study was to evaluate the occurrence of weeds, nutritional state and yield of maize - B. brizantha intercrop under different layouts of Brachiaria pasture sowing treated with the herbicide mixture nicosulfuron + atrazine and atrazine. In the plots, the treatments consisted in maize and B. brizantha sowing in single crops, besides four forms of establishing B. brizantha by sowing one and two rows of B. brizantha in-between the maize rows; sowing along the same row as maize; and sowing the forage scattered in-between the maize rows. In the subplots, the two secondary treatments consisted in using the herbicide mixture nicosulfuron + atrazine (8 + 1,500 g ha-1) and atrazine (1,500 g ha-1) applied 30 days after emergence (DAE). Dry biomass of the macronutrient levels, grain yield and the weight of a thousand maize kernels, as well as the total dry matter yield and macronutrients accumulated by the pasture were evaluated. The weed species Brachiaria plantaginea, Brachiaria decumbens, and Sorghum arundinaceum were controlled by the mixture nicosulfuron + atrazine; the species Digitaria horizontalis, Cyperus rotundus, and Artemisia verlotorum were not controlled by the herbicide mixture. Lower levels of total chlorophyll and N leaf contents in maize were observed when two rows of B. brizantha were cultivated in-between the maize rows. When the herbicide mixture nicosulfuron + atrazine was used, highest levels of total chlorophyll, N, P, and K, grain yield, and weight of a thousand kernels were observed in maize compared to the treatments without product application. When two rows of B. brizantha were cultivated in-between the maize rows, a greater occupation of soil by the cultivated species, greater yield forage and greater amount of nutrients incorporated of this biomass were observed, without significantly affecting maize yield grain.

Selectiveeffectsof natural and synthetic insecticideson mortality of Spodopterafrugiperda(Lepidoptera: Noctuidae) and its predator Eriopis connexa(Coleoptera: Coccinellidae)

Abstract: SpodopterafrugiperdaSmith(Lepidoptera: Noctuidae) is a serious pest of com in severalAmericancountries. It is mainlycontrolled with synthetic insecticides. The objectives of this study were to evaluate the effects of the natural products, neem oil and pyroligneous extract, and the synthetic insectieide,lufenuron, at 2.5OmLwater (0.25 %) on the mortality of 2-,4- and 6-day-old eaterpillars of S.frugiperda, and their selectivitiesagainst fourth instar larvae of Eriopis connnexaGermar (Coleoptera: Coccinellidae).Four- and 6-day-old S.frugiperda caterpillars showed higher mortality after exposure to neem oil (83.33::1:0.83 and 89.58::1:0.90 %, respectively) and lufenuron (95.83::1:0.96 and 85.41 ::I:0.83 %), compared to pyroligneous extraet (68.75 ::I:0.69 and 31.25 ::I:0.31 %). The deleterious effect of pyroligneous extract was higher in 2- (83.33 :I: 0.83 % mortality) and 4-day-old (68.75:1: 0.69 %) S.frugiperda caterpillars than in 6-day-oldcaterpillars (31.25:I:0.31%). Larvalmortality of the predator E.connexawaslowerwithneemoil and pyroligneous extraet (25.00:I:0.33 %) than with lufenuron (91.66:I: 1.22%). Neem oil is thus recommendedfor control of S.frugiperda because of its high toxicity, combined with its relatively low toxicity to larvae of the natural enemy E. eonnexa.

Extracellular biosynthesis of silver nanoparticles using the cell-free filtrate of nematophagous fungus Duddingtonia flagrans

Abstract: The biosynthesis of metallic nanoparticles (NPs) using biological systems such as fungi has evolved to become an important area of nanobiotechnology. Herein, we report for the first time the extracellular synthesis of highly stable silver NPs (AgNPs) using the nematophagous fungus Duddingtonia flagrans (AC001). The fungal cell-free filtrate was analyzed by the Bradford method and 3,5-dinitrosalicylic acid assay and used to synthesize the AgNPs in the presence of a 1 mM AgNO3 solution. They have been characterized by UV-Vis spectroscopy, X-ray diffraction, transmission electron microscopy, dynamic light scattering, Zeta potential measurements, Fourier-transform infrared, and Raman spectroscopes. UV-Vis spectroscopy confirmed bioreduction, while X-ray diffractometry established the crystalline nature of the AgNPs. Dynamic light scattering and transmission electron microscopy images showed approximately 11, 38 nm monodisperse and quasispherical AgNPs. Zeta potential analysis was able to show a considerable stability of AgNPs. The N-H stretches in Fourier-transform infrared spectroscopy indicate the presence of protein molecules. The Raman bands suggest that chitinase was involved in the growth and stabilization of AgNPs, through the coating of the particles. Our results show that the NPs we synthesized have good stability, high yield, and monodispersion.