Rogério Faria Vieira

Espectro de gotas de bicos de pulverização hidráulicos de jato plano e de jato cônico vazio

A escolha e o uso adequado de bicos de pulverizacao sao essenciais para a correta aplicacao de agrotoxicos. Este trabalho teve como objetivo avaliar o espectro de gotas de bicos de pulverizacao hidraulicos de jato plano padrao e de jato conico vazio, com diferentes vazoes nominais. Em ambiente controlado, avaliou-se o espectro de gotas por meio de um analisador a laser de gotas em tempo real, nas faixas de pressao de 200 a 400 kPa para os bicos de jato plano, e de 400 a 600 kPa para os bicos de jato conico vazio. Realizou-se tambem um estudo teorico sobre a distância horizontal percorrida por gotas de tamanho conhecido. Os bicos de jato conico vazio apresentaram gotas de menor tamanho em relacao aos de jato plano e, por isso, proporcionaram maior densidade de gotas depositadas sobre a superficie-alvo. Todos os bicos apresentaram densidade de gotas superior a 110 gotas cm-2. No entanto, o potencial de deriva foi alto, principalmente o dos bicos de jato conico, requerendo estrategias para sua reducao. E possivel estimar a distância horizontal percorrida por gotas de tamanho conhecido.

Deposição e deriva de calda fungicida aplicada em feijoeiro, em função de bico de pulverização e de volume de calda

The fungicide application technology should provide efficient control of vegetable diseases. The objective of this study was to evaluate the deposition and the drift of fungicide sprayed in a common bean crop with different nozzles and two volumes of application. A completely randomized block design with four replications was used, in a factorial model 2 x 2: two spray nozzles (standard flat fan and hollow cone) and two spray volumes (125 and 250 L ha-1). The study of deposition was made by a tracer analysis in different positions of the crop, using spectrophotometer. The drift was evaluated using artificial targets placed outside the application area. The fungicide, with the tracer was applied three times, using a CO2 - pressurized sprayer. The results allowed the following conclusions: the flat fan and hollow cone nozzles provided similar cover of the bean leaves, both in the superior and the inferior position of the crop; the application volume of 250 L ha-1 provided higher retention of fungicide in the leaves and higher uniformity of coverage of the plants than the volume of 125 L ha-1; the droplets formed in the application with hollow cone nozzles were more favorable to the drift than the ones produced with flat fan nozzles, specially when low application volume was used; and the applications, in general, provided low deposition uniformity and high drift potential.

White mold intensity on common bean in response to plant density, irrigation frequency, grass mulching, Trichoderma spp., and fungicide

The purpose of this study was to evaluate the efficiency of integrated managements on white mold control on common bean. Initially, in vitro testing was made to assess the antagonism of 11 Trichoderma isolates against Sclerotinia sclerotiorum and to investigate fungicides (fluazinam and procymidone) inhibitory effects on those fungi. In two field experiments the following combinations were tested: irrigation frequencies (seven or 14 days), plant densities (six or 12 plants per meter), and three disease controls (untreated control, fungicide or Trichoderma spp.). In a third experiment plant densities were replaced by grass mulching treatments (with or without mulching). Fluazinam was applied at 45 and 55 days after emergence (DAE). The antagonists T. harzianum (experiments 1 and 3) and T. stromatica (experiment 2) were applied through sprinkler irrigation at 10 and 25 DAE, respectively. Most of the Trichoderma spp. were effective against the pathogen in vitro. Fluazinam was more toxic than procymidone to both the pathogen and the antagonist. Fungicide applications increased yield between 32 % and 41 %. In field one application of Trichoderma spp. did not reduce disease intensity and did not increase yield. The reduction from 12 to six plants per meter did not decrease yield, and disease severity diminished in one of the two experiments. It is concluded that of the strategies for white mold control just reduction of plant density and applications of fungicide were efficient.

Characterization of genetic variability among common bean genotypes by morphological descriptors

The purpose of this study was to characterize the genetic variability in 100 genotypes of the Active Germplasm Bank of common bean of the Federal University of Vicosa, by morphological descriptors, classify them in groups of genetic similarity and to identify the degree of relevance of descriptors of genetic divergence. The genotypes were evaluated based on 22 quantitative and qualitative morphological descriptors. The high-yielding genotypes V 7936, Gold Gate, LM 95103904, 1829 S 349 Venezuela, and PF 9029975, CNFC 9454 and Fe 732015, with upright growth, have potential for use as parents in common bean breeding programs. By genetic divergence analysis, the genotypes were clustered in eight groups of genetic dissimilarity. By methods of principal components, 9 of the 22 descriptors were eliminated, for being redundant or little variable, suggesting that 10-20 morphological descriptors can be used in studies of characterization of genetic variation.

Avaliação de pontas de pulverização hidráulicas na aplicação de fungicida em feijoeiro

The spray nozzles are one of the most important components of pesticide hydraulic sprayer because they affect the characteristics of the emitted spray. The objective of this study was to evaluate three hydraulic spray nozzles (standard flat fan, low drift flat fan and hollow cone) for bean diseases control upon application of the fungicide chlorothalonil applied at 20, 30, 40 and 50 days after emergency (DAE) in a water volume of 125 L ha -1 . For comparison, a non-treated plot was used. A randomized complete-block design with four replications was used. The first symptoms of anthracnose, angular leaf spot and rust were observed at 20 DAE. The droplet density obtained with the three spray nozzles was above 60 droplets cm -2 . The fungicide applied with the three nozzles provided satisfactory control of the diseases and there were no differences among nozzles. On average, bean yield increased 76% due to the fungicide applications.

Fungicidas aplicados via água de irrigação no controle do mofo-branco no feijoeiro e incidência do patógeno na semente

The effectiveness of four fungicides applied through irrigation water to control white mould of common beans (Phaseolus vulgaris) was evaluated in Vicosa, MG. The trial was installed on April in a naturally infested field with sclerotia of Sclerotinia sclerotiorum. The following fungicides and rates of active ingredient per hectare were tested: benomyl (1.0 kg), iprodione (0.75 kg), procymidone (0.5 kg), and fluazinam (0.5 l). Simulating sprinkler irrigation, fungicides were applied with watering-cans over the plants at 39 and 52 days after emergence (DAE) with water volume of 35,000 l/ha. At these two periods, fluazinam was also applied by a backpack sprayer (667 l/ha) or with watering-cans (35,000 l/ha) between the rows and near the soil surface. The last treatment was to verify the fluazinam effect on white mould control when applied on the soil surface. An untreated plot was also included. After harvest, seed transmission of the pathogen was evaluated. Fluazinam (applied either by backpack sprayer or through irrigation water onto plants), benomyl, and procymidone were the most efficient fungicides for white mould control. Among them, only procymidone did not provide yield higher than that of control. Fluazinam applied only on soil reduced white mould incidence and the amount of sclerotia produced. Yields varied from 1,406 kg/ha (control) to 2,054 kg/ha (fluazinam applied by backpack sprayer). There was no effect of treatments on the pathogen seed transmission, which varied from 0.25% (procymidone) to 1.08% (fluazinam applied only on the soil).

Management of white mold in type III common bean with plant spacing and fungicide

White mold is a yield-limiting disease during the fall-winter season in southeastern Brazil when irrigated type III common beans are generally sown 0.5 m apart with 10 to 12 plants per meter. The aim of this study was to evaluate the efficacy of combining increased row width (RW) and reduced planting density (PD), with or without fungicide, for white mold management. Treatments were arranged as a 23 factorial: RW (0.50 or 0.75 m), PD (6 or 12 plants per meter), and fungicide (sprayed or unsprayed). Two trials were conducted in Vicosa, State of Minas Gerais. In 2002, the average incidence of white mold was 43.2%, the severity index, 31.1%, and the yield, 2513 kg ha-1. In 2003, the values of these variables were 48.0%, 22.6%, and 2159 kg ha-1, respectively. Interactions involving both RW and PD were not significant for either disease intensity or yield in the combined analysis across years. Increasing RW led to reduction in white mold intensity in 2002. The lower PD reduced disease incidence in 2002 and did not affect yield in the combined analysis. In fungicide sprayed plots, wide RW decreased yield in 2002, but RW did not affect yield in 2003. In unsprayed plots, RW did not affect yield in both years. We conclude that increasing RW to 0.75 m combined with low PD is a promising strategy for white mold management when fungicide is not applied. When fungicide is applied, the current row width (0.50 m) combined with low PD maximize the yield.

Foliar application of calcium chloride and calcium silicate decreases white mold intensity on dry beans

White mold (Sclerotinia sclerotiorum) is the most important common bean disease during the fall-winter season in Brazil. Different control strategies are necessary to control this disease and increase bean yield in infested areas. The aim of this research was to evaluate the effect of application of calcium chloride (CaCl 2 ) and calcium silicate (CaSiO 3 ) on white mold control on common bean. The experiment was carried out during the 2006 fall-winter season in Vicosa MG, Brazil, in a field naturally infested with sclerotia . Both CaCl 2 and CaSiO 3 were applied at 45 days after emergence (DAE) (early bloom) over the plants with a hand sprayer (800 L ha -1 ) at the rates of 100, 200, 300 and 400 mg L -1 or at 45 and 55 DAE at 300 mg L -1 . Two additional treatments were used: water (untreated control) and the fungicide fluazinam (0.5 L ha -1 ) applied at 45 and 55 DAE. Both incidence and severity of white mold were significantly reduced with application of CaCl 2 and CaSiO 3 , but there was no effect on yield. Fluazinam reduced significantly the disease incidence and severity by 52% and 73%, respectively, and increased the yield by 31%.

Chemigation with benomyl and fluazinam and their fungicidal effects in soil for white mold control on dry beans

The effectiveness of fungicides in controlling white mold (Sclerotinia sclerotiorum) of dry beans (Phaseolus vulgaris) was evaluated when they were applied through irrigation water directly onto the plants or only to the soil. Two field trials were installed in April 1998 and April 1999 in Vicosa, MG. Trials were conducted as a (2 x 3) + 1 factorial: two fungicides x three application modes + one untreated control. The fungicides were benomyl (1.0 kg a.i. ha-1) and fluazinam (0.5 l a.i. ha-1). The three application modes were: (a) by backpack sprayer (667 l ha-1), (b) by garden watering-cans simulating sprinkler irrigation with 35,000 l ha-1 of water, and (c) by garden watering-cans applying water between the rows and near the soil surface in 35,000 l ha-1 of water. In 1998, fungicides were applied at 43 and 54 days after emergence (DAE); in 1999, at 47 and 61 DAE. Both fungicides were similarly effective on white mold control when applied by either chemigation or backpack sprayer, resulting in yields 21% higher than untreated control. Only fluazinam provided disease control when applications were made only in soil. Chemigation provided white mold control equivalent to that of backpack sprayer in terms of incidence, severity and number of diseased pods. Consequently, yield differences between these application methods were not significant.

BRSMG Madrepérola: common bean cultivar with late-darkening Carioca grain

The cultivar BRSMG Madreperola, recommended for cultivation in Minas Gerais, has the feature of maintaining a light grain color for a longer period than other Carioca grain cultivars. The yield potential is high and the resistance level good to the major anthracnose races in the region.