Repositório RCAAP

 The water index used in this study (ETr/ET0) is the relation from the real evapotranspiration to the potencial or referential evapotranspiration, for a given subperiod of the sunflower cycle. For the study of the relation between the sunflower grain production and the water index above referred, were avaliatedVcrop data, involving yield and phenology, obtained from 53 experiments of cultivars evaluation; meteorological daily data of solar radiation, air temperature, rainfall, air relative humidity, and wind velocity; sou data related to the storage of available water; and the definition of the four subperiods of sunflower development, crop establishment, vegetative, reproductive, and grain physiological maturity. The results showed a high assotiation betweenn grain yield and the water index in the reproductive subperiod, followed by the vegetative, and the final filling grain until physiological maturity subperiod.

Pathogens establish complex interactions pattems with plants, which can be compatible or not. Considering the different plants which daily supply human needs, and all diseases caused by viroses, bacteria, fungi and nematodes which can cause damage to these plants, the number of host/pathogen combinations is immense. Besides that, the exchange of plants between different regions and the intensivo system of agriculture helped the dissemination and evolution of these combinations. Tissue culture techniques, which provide a efficient control of the environment conditions, and tum possible to analyze a wide number of genetic material in restrict space, can help the study of host/pathogen interactions, and breeding programs on the development of disease-resistant plants. 

This research was carried out at Taquari Experimental Station, in order to study the influence of ten rootstocks and three scions of orange in the incidence of the citrus rust mite. The scions of orange cultivars [Citurs sinensis (L.) Osbeck] were 'Valência', 'Hamlin' and 'Seleta Franck'.The rootstocks were: 'Troyer', 'C-20', 'C-65' and 'C-41' citranges [P. trifoliata (L.) Raf. x sinensis (L.) Osbeck]; 'Cleopatra' mandarin (C. reshni); 'Volkameriana' (C. volkameriana); 'Florida' and 'Naci onal' rough lemon (C. jambhiri); 'Taquari' rangpur lemon (C. limonia) and 'Caipira' sweet orange [C. sinensis (L.) Osbeck]. The estimate of the population was made at 15 days of interval. The sampling was based in ten leaves per plant, in five areas with one centimeter of diameter, in each leave. The results support the conclusion that the highest incidence of citrus rust mite occurred in plants with the rootstock ‘Troyer' citrange; the scion of 'Seleta Franck'sweet orange was more infested; between scions of 'Valência' and “Hamlin' sweet orange wasn't difference.

The State of Rio Grande do Sul is the main grain producer in Brazil, responsable for 25% of national grain production. On average, the State has had losses in 3 of every 10 harvest, especially due to droughts and floods. Previous studies have shown a good relationship ' between the variability of rainfall and ENSO. The objective of this study is to evaluate the influence of ENSO over rainfall and maize yield in the State of Rio Grande do Sul. We analysed the relationship between rainfall, maize yield, Southem Oscilation Index (I0S) and Sea Surface Temperature (SST) from Pacific Ocean. The results showed that the variability of rainfall in the State of Rio Grande do Sul is associated with ENSO phenomena, and this variability has influence over the variability of maize yields in the State. These information can be incorporated in yield si mulation models in order to identify strategies to mitigate the impacts of the climate variability over maize production. 

The growth of sunflower was evaluated during two growing seasons (1991/92 and 1992/93) in Taquari-RS. The study involved cultivars, fertilization leveis and date of seeding, under non limiting water conditions. Growth rate and net assimilation were strongly associated with air temperature. Leaf Area Index (LAI) showed a strong relationship with the Degree days. The low temparatures determined elongation of subperiods and on the duration of growth cycle. There was no response to photoperiod. The later cultivar showed a higher biological yield than the early cultivars evaluated. The fertilization leveis evaluated did not show any differences on the sunflower development and this was dueto the high fertility levei of the local soil. 

 A field experiment was carried out on a plinthosol at the Agronomic Experimental Station, Federal University of Rio Grande do Sul, located in Eldorado do Sul (30 ° 05' 52" 5, 51' 39 08" W), from October 1993 to July 1994, to evaluate eleven herbicides on weed control and herbicide selectivity to alfalfa. The herbicides were tested when alfalfa was at the seedling establishment stage. Two control treatments were included: with and weed-free plots. A randomized complete block design with four replications was used. Treatment effects were evaluated in terms of alfalfa seedling number after germination, alfalfa early growth and herbicide injury, control of pigweed (Amaranthus deflexus L.) and Brazil pusley (Richardia brasiliensis Gomez). Alfalfa and weed dry matter yields after four harvests were also considered. EPTC (4000 gai/ha) preplant incorporated (PPI), trifluralin (2400 gailha) preemergence (PRE) and imazethapyr (100 galha) postemergence (POST) showed the best overall performance when selectivity, weed control and alfalfa DM yield are considered as a set of relevant agronomic parameters to the alfalfa crops. The herbicides linuron and exadiazon were very toxic to alfalfa. 

Growth and maximum yield (Ym) of sunflower was modeled based on the effective temperature (degree-day s) and photosyntheticaly active radiation absorved and accumulated (PARaa) under well watered conditions. Experimentawere performed on a field site at Taquari (RS) during two growth seasons (1991/92, 1992/93). The results showed that theleaf ares index (LAI) can be stimated from the sum of the efective temperature. The absortion of PAR is very closelyassociated with the LAI and the canopy structure, that is represented by the extinction coeficient (K).

Products formulated from plants have a range of active compounds, which may have proven insecticidal effects and can be attractive or repellent to insects, thus serving as an alternative in the control of populations of insect pests. The present study aimed to investigate the potential insecticidal activity of essential oils and methods of application on Sitophilus spp. in beans (Phaseolus vulgaris) under controlled atmosphere. The bioassays were conducted at the Laboratory of Entomology of the Agronomy Department of the Southern University of Santa Catarina (UNISUL). The essential oils used were: Cymbopogon citratus (citronella), Cymbopogon nardus (lemon grass) and Pimenta racemose (peppercorn), which were applied in two methods on bean grains. An insecticidal effect on Sitophilus spp due to the application of essential oils in bean grains. Greater insecticidal effect was obtained especially in the treatment with peppermint essential oil, and the second highest average mortality was presented by lemon grass oil. These results show that these two oils are efficient for handling Sitophilus spp. within 72 hours after application.

The above ground biomass production and maximum yield (Ym) of sunflower were modeled based on theeffective temperature (Degree-Days) and photosyntheticaly active radiation absorved and accumulated (PARaa), under wellwatered conditions. Experiments were performed at a field sita at Taquari-RS, during two growth seasons 1991/92 and 1992/93. The energetic efficiency of sunflower was 2.457 grams of above ground dry manar per megajoule of PARaa during theperiod from emergence to the end of anthesis. The results also showed that the maximum yield of sunflower can be estimatedbased on the climatic normals of solar radiation and temperature for a given region.

Phenoxy compounds have been utilized as herbicides in wheat crop for almost five decades. Compouds with different modes of action, like bentazon, diclofop, and pendimethalin, have more recent use. The objective of this research was to evaluate wheat tolerante to these herbicides under field and weed-free conditions. It was found that the herbicides affected negatively the wheat cultivar tested, being the hormone like herbicides and their mixtures those that caused the greatest injury. Regarding grain yield, 2,4-D formulations amine and ester were equivalents. Wheat characteristics more affected were: plant height, test weight, and grain yield. Among the hormone type products, MCPA proved to be the most tolerated by wheat crop. For the majority of variables evaluated, diclofop, pendimethalin, and bentazon were the compounds better tolerated by wheat, nevertheless the last reduced its grain yield. 

Water deficit is the main factor responsible for reductions in maize production at Rio Grande do Sul State,Brazil. Therefore, quantifying the relationship between water availability and grain yield will give to us important informationsto help improve production in thc state. In this study, we looked at the relationships between grain yield and water availabilityusing a multiple regression models and Jensen model, which relates productivity to relative water use (ETr/ETm) at differentstages during the crop cycic. The data on grain yield and phenology were obtained from experiments conducted at Taquari,São Borja, Santo Augusto and Veranópolis experimental stations, during the periods from 1975/76 to 1989/90. The analisyswas performed for two maturity groups separately (early and normal), with a total of 89 data points for each of the groups.Based on the available data, both models were good estimators of com yield. Comparing the models results to the actual data,we notice a strong relationship between the relative yield observed and estimated with correlation coefficient varying from0.893 to 0.946.

In order to control blue mold on apple the following fungicides were tested with dosage of a.i./h1: Methyl tiofanate— 0,07; dicloran — 0,125; methyl tiofanate + dicloran — 0,07 + 0,100; triflumizole — 0,03; diniconazole — 0,0025 and thiabendazole-0,09. The fruits were inoculated with Pencillium expansum. Dicloran and triflumizole were superior to other treatments but no total control of blue mold were observed. 

This study was conducted with the objective of identifying the main forros by which the organic N occur in ten soils of Rio Grande do Sul-Brazil as determined by two methods of successive hydrolysis. Among the methods the fractions was extracted from soils by applying different acid concentration and hydrolysis periods, to obtain hydrolyzed of IN HC1/3h (H1), 3N HC 1/3h (112), 6N HC1/4h (113) and 6N HCl/20h (I14). For methods differentiation, a second hydrolysis was performed in these hydrolyzed with propionic and perchloric concentrated acids for the estimation of the a-anino-N fraction. The method with only one hydrolysis was inefficient for characterizing the a-amino-N fraction, whereas the method modification proposes by the same authors enhances the extraction of thus fraction with a consequent decrease of the nonidentified-N fraction. A methodological simplification was applied in the foir described hidrolyzate stages with the objective of reducing then to half, obtaining, in this way, only Hl and H2 data, and estimating by equations the total of four stages. This simplification underestimated the values of the N-organic fractions. As a result new equations were adjusted, showing a better estimation of the different fractions. About 63% of the hydrolyzed-N was recovered during the first two stages of the successive hydrolysis (H1 and 112), the remaining being a more recalcitrant fraction present in the last two stages (113 and 114). 

The results of bacteriological studies of 102 milk samples from cows in a herd with ligh prevalence ofclinicai and subclinical mastitis yelding 36 isolates of the yest Candida albicans are described.The relationship between the aetiological agent of yeast intramammary infection and some epidemiological espoeis of theherd, associated with the failure of the long term antibacterial therapy is analysed.

Performance of Fluazuron, a tick development inhibitor was evaluated against the cattle tick Boophilusmicroplus al dosages of 1 mg/kg and 2 mg/kgthrought pour-on formulation on caule kept in field conditions, and experimentallyinfested. Results were compared with a bovine group treated with Cypermethrin and a control group. Adult females collectedin the days +2 and +4 after treatment (a. t.) did not show any morphological changes or inhibition in the development, butfemales between +7 and +35 days a. t. showed alterations in the size, form and aspect, beeing easily ruptured duringmanipulation. The majority did not lay eggs during this period. From the day +14 a. t. there was a marked difference betweenthe average number of ticks in the groups treated with Fluazuron and the control. In the day +58 a. t. there was no differencein the group treated with Fluazuron (1 mg/kg), Cypermethrin and the control but the group with 2 mg/kg showed a lowernumber of ticks. The group treated with 2 mg/kg showed a slighty low number of ticks between the days +7 and +58 a. t. incomparison with 1 mg/kg and in the day +25 there was no tick in this group. In all the groups there were ticks surviving in theear surrounding region.

 Serologic tests were performed in 1545 serum samples collected from pigs in 83 farms of the State of Rio Grande do Sul, Brazil, in the period of April, 1994 to April, 1995. Part of the farms had a history of reproductive disorders (31 herds, 654 samples), while the remaining sem derived from farms free of reproductive abnormalities (52 herds, 891 samples). Results of microscopic agglutination tests showed 121 (13.58%) positive reactors (titer equal or greater than 1:100) in the free herds. In the herds with history of reproductive disorders, 276 (42.9%) of the sera were positive. Positive titers for L. bratislava (57.2%) and L. icterohaemorrhagiae (13.76%) were more preválent in farms with reproductive problems. There was also cross reaction to these serovars.

This research was carried out at São Sebastião do Caí county, to study the acaricide action of various pesticides against the citrus flat mite, in a 'Valencia' orange orchard. The treatments and quantities of active ingredient, per plant, were: pyridaben 1.0, pyridaben 1.5, pyridaben 2.0, diflubenzuron 0.625, diflubenzuron 1.25, diflubenzuron 1.875, pyridaben 1.0 plus mineral oi137.8, pyridaben 1.0 plus sulfur 20.0, sulfur 40.0, fenbutatin-oxide 3.75, DEB 01283 3.5, DEB 01283 3.5 plus DE 01986 80.0, fenpropathrin 0,75 plus clofentezine 2.5, fenpropathrin 0.75 plus clofentezine 1.25, fenpropathrin 1.5 plus clofentezine 1.25, and check..The estimate of the popúlation was made one day before the pulverization and 3, 23, 36, 53 and 72 days Aer. The sampling was based in 10 leaves and tive fruits per plant. The results support the conclusion that all the products tested were efficient to control the citrus flat mite.

This research was carried out at Taquari Experiment Station, to study the insecticide action of various pesticides against the citrus snow scale, in a 'Valencia' orange orchard. The treatments and quantities of active ingredient, in grams per plant, were: flufenoxuron 0.375, flufenoxuron 0.375 plus mineral oil 40.0, teflubenzuron 0.375, teflubenzuron 0.375 plus mineral oil 40.0, mineral oil 40.0, malathion 0.75 plus mineral oil 40.0, buprofezin 1.25, buprofezin 2.50, buprofezin 1.25 plus mineral oil 37.8, mineral oil 37.8 malathion 0.75, plus mineral oil 37.8, malathion 0.75, and check. The estimate of the population was made 18 and 56 days after the pulverization of the products. On each plant, two arcas of 10 cm' were marked on the infested stems and branches, one day before spraying. From the results obtained, the more .efficient products were malathion plus mineral oil, buprofezin plus mineral oil and malathion. 

This research was carried out at Taquari Experiment Station, in order to study the acaricide action of various pesticides against the citrus rust mite, in a 'Seleta Franck' orange orchard. The treatments and quantities of active ingredient, in grams per plant, were: sulphur 28.8, sulphur 48.0, sulphur 67.2, carbosulfan 1.2, bifenthrin 0.6, fenbutatin-oxide 1.8, and check. The estimate of the population was made one day before and 7, 14, 21, 28, 45 and 60 days after the pulverization of the products. The sampling was based on 10 leaves per plant, collected around the tree. The counting of mites was performed in five points in the upper face of the leaves, with stereoscopic microscope adjusted for 20 x, being three along the middland veio and two on the larger face of the leaf. The results support thc conclusion that sulphur (28.8 g A.I./plant and 48.8 g A.L/plant) and carbosulfan were efficient until 45 days after the pulverization. The more efficient acaricide was fenbutatin-oxide and the less efficient was bifenthrin. 

This study was carried out in 1987, at Centro de Pesquisa e Extensão em Fruticultura Tropical —CEPEX (Research and Extension Centre on Tropical Fruits), located in Porto Lucena,RS, Southem Brazil (27°51'24" S, 55 °01'09" W), to evaluate the effect of six plant spacing on the production and mean fruit weight of Yellow Passion Fruit. Plant spacing used was: 1.25, 2.0, 2.75, 3.5, 4.25 and 5.0 m within the rows which were 2.5 m apart. The statistical analysis showed an increasing linear effect on total plant production and number of fruits per plant as plant spacing increased. Neverthless, there was no effect of plant spacing on the total production and total fruit number per hectare. Results for mean fruit weight showed an oscillating effect, as plant spacing increased. According to this experiment it is suggested that wider plant spacing is more advisable due to an increase on plant production, at a small cost, and no decrease on total production per arca.