Walter Boller

Avaliação de diferentes manejos de solo e métodos de semeadura em área sob sistema de plantio direto

Aiming to evaluate the response of corn to different soil tillage systems and seeding methods under no tillage, a field trial was conducted at the Faculdade de Agronomia da Universidade de Passo Fundo, RS, in 1993-94. Four treatments (no tillage system; disk plow + disking; chisel plow + disking and prototype chisel plow) and two seeding types (hoe type planter and offset double disk) were used. Grain yield of com and soil density were evaluated after corn harvesting. Corn yield was significantly affected by hoe type planter, mainly for the no till treatment. The soil density results showed more compaction on the surface layers on the no tillage treatment, howewer no difference among treatments was observed for deeper soil layers. It was concluded that narrow knife used on the planter eliminates soil compaction problems, proportioning better rooting of plante.

Quantificação de propágulos de Gibberella zeae no ar e infecção de anteras em trigo

Devido ao aumento da ocorrencia e da intensidade de epidemias nos ultimos anos, a giberela tem sido apontada como uma das doencas que mais danos causa em cereais de inverno. O principal inoculo do fungo patogeno (Giberella zeae) sao os ascosporos produzidos em peritecios sobre os restos culturais da maioria das especies cultivadas. Os esporos sao transportados a longas distâncias pelo vento e depositados sobre as anteras causando infeccao. Os objetivos do presente trabalho foram quantificar a densidade de esporos no ar, a incidencia da infeccao em anteras de trigo (Triticum aestivum), a intensidade da doenca no campo e elucidar o papel das anteras no processo infeccioso. Durante o periodo correspondente a antese do trigo, foram coletados, em media, 6,6 esporos/10 cm 2 /dia, em 1999 e 13,5 esporos/10 cm 2

Quantificação de danos causados pela giberela em cereais de inverno, na safra 2000, em Passo Fundo, RS

one of triticale (Triticum x secale ), three of barley (Hordeum vulgare), and six of wheat (Triticum aestivum). Spikes were sampled from 75m 2

Efeito da época, do número de aplicações e de doses de fungicida no controle da giberela em trigo

Head blight is one of the most damaging wheat (Triticum aestivum) diseases, causing reduction of grain yield, grain quality, flour protein levels, seed germination and vigor, and production of micotoxins. Head blight is considered a floral disease because the fungus enters the host plant through the anthers during anthesis. Occurrence of head blight is conditioned by temperatures above 20 °C and wetness periods longer than 72 h. This research aimed at studying the timing during anthesis for fungicidal sprays, the effect of rates of fungicide and number of sprays on head blight control and on grain yield and quality. Uneven anthesis is the main cause for the low efficacy of fungicides in the field. Even six and seven sprays during anthesis did not eradicate the disease (maximum control of 91%). Two and three applications improved the disease control over one spray. On average, the fungicidal sprays controlled head blight by 67% and increased grain yield by 32%. These results showed that chemical control of head blight is useful and would be practical at full anthesis, with no rate reduction recommended.

Técnicas de aplicação de fungicida em trigo para o controle de Giberela (Gibberella zeae)

For many years, the head blight of winter cereal crops, caused by the fungus Gibberella zeae, was considered a disease of secondary importance. However, the increased frequency and yield losses associated with head blight in Southern Brazil have turned this disease into a major problem. Gibberella zeae enters the host plants through the anthers. To avoid infection, the fungicides need to protect the anthers from the fungus, which requires improved spray techniques. The role of two types of spray nozzles (single jet and twin jet), different nozzle arrangements, and two spray volumes on head blight control and grain yield were evaluated. The experiments conducted at the field, during the year 2000, showed that the fungicidal applications reduced disease incidence, the number of infected spikelets, and disease severity significantly. The grain yield was increased as well. The spray nozzles, nozzle arrangements, and spray volumes did not influence disease control and grain yield. The differences in grain yield between treated and non-treated plots made chemical control worthy, despite its low efficacy. Fungicidal sprays to control head blight should use nozzles that deliver medium to fine droplets, at a volume of 200 L.ha-1.

Efeito da pressão de trabalho e de modelos de pontas de pulverização sobre a eficiência de herbicida de contato em soja

In recent years, contact herbicides have been sprayed, with reduced spray volumes, using spray nozzles that work at low pressures. To evaluate the flat fan spray nozzles of Teejet series XR, DG, TT and AI operated at different pressures, it was conducted an experiment for hairy beggar ticks (Bidens spp.) control. The experiment was carried out in Passo Fundo Municipality (Brazil), using bentazon contact herbicide in a soybean culture. The XR 110015, DG 110015 and TT 110015 nozzles were operated with pressure levels of 100; 200 and 300 kPa, and the AI 110015 nozzle with pressures of 200; 300 and 400 kPa. It was evaluated the hairy beggar ticks control at 7; 14 and 21 days after treatment and the grain yield of soybean. The AI 110015 nozzle showed inappropriate for this herbicide application in all evaluated pressures. Pressure of 100 kPa for the series XR, DG and TT, nozzles, were inadequate to use for contact post emergence herbicide application. All evaluated nozzles showed improved efficiency with the increase of pressure.

Fungicidas, doses e volumes de calda no controle químico da ferrugem da folha da aveia (Puccinia coronata f. sp. avenae)

Crown rust (Puccinia coronata f. sp. avenae) is the most important disease of oats in Brazil. In susceptible oat cultivars, fungicides are needed to control the disease efficiently. However, spray at low volumes may reduce fungicide performance significantly. A field experiment with the oat cultivar UPFA-20 was carried out at the FAMV/UPF to evaluate the influence of fungicides, rates, and spray volumes on the efficacy of the chemical control for crown rust. The tested treatments combined two fungicides (tebuconazole, Folicur, 0,75 L ha-1; epoxiconazole + pyraclostrobin, Opera, 0,5 L ha-1), four rates (40; 60; 80 and 100% of the commercial rate), and two spray volumes (100 and 200 L ha-1). The field plots were arranged according to a factorial block design (2´4´2) with four replicates. The assessments included the disease severity, disease control, grain quality and grain yield. The net profit of each treatment was also determined based upon the application costs and the sale price of oats at the harvest. At the same rate, for both fungicides, the volume of 200 L ha-1 provided better disease control. At this volume, the 50% rate controlled crown rust as good as the full (100%) rate with 100 L ha-1. The net profit differed between fungicides but not for spray volumes. The rate effects were fungicide dependent.

In vitro Determination of Fungicide Inhibitory Concentration for Phakopsora pachyrhizi isolates

In vitro assays were preformed to obtain the IC50 of eight fungicides against Phakopsora pachyrhizi isolates from Passo Fundo, RS, Ponta Grossa, PR, and Primavera do Leste, MT. Different concentrations of the fungicides were added to Petri dishes containing soybean leaf extract agar medium. One milliliter of P. pachyrhizi uredospore suspension at the concentration of 3.0 x 104 uredospores/mL was added to each dish for subsequent viability quantification. Only pyraclostrobin and the mixture trifloxystrobin + prothioconazole showed IC50 values inferior to 1.0 mg/L for all tested isolates, demonstrating high fungitoxicity. There was not loss of sensitivity to any of the tested fungicides.

Modificação de uma barra de pulverização para a aplicação de fungicida em trigo visando ao controle de giberela

The increased frequency and yield losses in wheat, associated with head blight in Winter cereal crops in Southern Brazil, caused by the fungus Gibberella zeae, have turned this disease into a major problem. Gibberella zeae enters the host plants through the anthers. To avoid infection, the fungicides need to protect the anthers from the fungus, which requires improved spray techniques. The role of different spray nozzles (flat fan, twin flat fan, and hollow cone), different nozzles arrangements, and two spray volumes on head blight control and grain yield were evaluated. In two experiments conducted in the field, at the year 1999, the fungicidal applications reduced significantly the disease incidence, the number of infected spikelets, and disease severity. The grain yield increased as well. The spray nozzles, nozzle arrangements, and spray volumes did not influence disease control and grain yield. The differences in grain yield between treated and non-treated plots made chemical control worthy, despite its low efficacy. Fungicidal sprays to control head blight should use nozzles that deliver medium to fine droplets, at a volume of 200 L ha-1.

AVALIAÇÃO DA DEPOSIÇÃO DE CALDA EM ANTERAS DE TRIGO, PARA O ESTUDO DO CONTROLE QUÍMICO DE GIBERELA (Gibberella zeae) 1

RESUMO: A giberela, causada pelo fungo Gibberella zeae (Fusarium graminearum), e uma importante doenca de infeccao floral do trigo. Para controlar essa doenca, o fungicida deve ser aplicado durante a antese, de modo a proteger as anteras. Os objetivos do presente trabalho foram de construir uma barra de pulverizacao que permitiu utilizar bicos em diferentes arranjos e quantificar a presenca de corante nas anteras quando aplicado com diferentes pontas de pulverizacao, direcoes dos bicos na barra e com diferentes volumes de calda. Utilizaram-se pontas de jato plano (XR-11002), jato plano duplo (110DB2) e jato conico vazio (JA-2), espacadas em 0,50 m, em uma barra tradicional e numa barra modificada. Na barra modificada, foram utilizados corpos duplos giratorios, posicionandose os bicos na vertical, 30o ou 45o para frente e para tras em relacao a vertical. Os resultados mostraram que a utilizacao de dois bicos no mesmo ponto da barra aumentou significativamente o numero de anteras que receberam o fungicida. As tres pontas de pulverizacao comportaram-se de maneira semelhante. Dois bicos formando ângulo de 30o em relacao a vertical proporcionaram a mesma quantidade de anteras cobertas com corante do que dois bicos posicionados na vertical. A angulacao dos bicos em 45o com a vertical proporcionou maior numero de anteras atingidas pela calda. PALAVRAS-CHAVE: barras de pulverizacao, pontas de pulverizacao, anteras soltas e presas.