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Search Results: 1 - 10 of 165509 matches for " Francisco F. Laranjeira "
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Comparative epidemiology of citrus tristeza in Cuba and citrus sudden death in Brazil
Batista, Lochy;Bassanezi, Renato B.;Laranjeira, Francisco F.;
Tropical Plant Pathology , 2008, DOI: 10.1590/S1982-56762008000500002
Abstract: citrus sudden death (csd) is a disease of unknown etiology, reported only in brazil. due to similarities between the epidemiology of csd in brazil and citrus tristeza (ct) in other countries, this work aimed to compare csd and ct in cuba. besides testing the hypothesis of shared epidemiological patterns, the data generated can be used to carry out control strategies if csd breaks out in cuba. seven epidemic data sets were statistically compared for each disease by analyzing their progress in time and the dependence among symptomatic or infected plants at two levels of spatial scale. csd and ct epidemics could not be differentiated based on mean progress rate, area under disease progress curves, proportion of aggregated sequences (ordinary runs test), index of dispersion (d) or both parameters, log (a) and b, of the binary power law model. the progress rate of both diseases varied from low (0.0003/month) to very high (0.045/month). the proportion of aggregated sequences was low (<0.16) and d, log(a) and b values indicated aggregation in groups of 4 to 16 plants for both diseases. these results suggest that measures currently used for ct eradication and management in cuba may be applied in case of an eventual introduction of csd in that country.
Dinamica temporal da Clorose Variegada dos Citros em três regi es do Estado de S o Paulo
Laranjeira Francisco F.,Bergamin Filho Armando,Amorim Lilian,Berger Richard
Fitopatologia Brasileira , 2003,
Abstract: Este trabalho objetivou esclarecer se o progresso da Clorose Variegada dos Citros (CVC) diferia entre três regi es de S o Paulo, distintas quanto à incidência da CVC em citrus (Citrus spp.). Foram avaliadas três áreas, Noroeste, Centro e Sul de S o Paulo, durante dois anos, em avalia es quinzenais, quando eram mapeadas as plantas sintomáticas. Tentou-se o ajuste de nove modelos ao progresso da doen a, além do ajuste de três modelos a segmentos das curvas originais. Foram estimadas também as diferenciais e as diferenciais secundárias de cada curva de progresso. Apenas quando as curvas foram divididas é que foram obtidos bons ajustes aos modelos de progresso. A diferencial (velocidade da doen a) e diferencial secundária (acelera o do aparecimento de novas plantas doentes) apresentaram diversos picos ao longo do tempo. Esses picos ocorreram em meses de Primavera e Ver o. Levanta-se aqui a hipótese de que os picos de diferencial - incomuns na quantidade encontrada - estejam relacionados a determinados picos de emiss o de brota es, já que as novas brota es s o o local preferido de alimenta o dos vetores de Xylella fastidiosa.
Dinamica espacial da clorose variegada dos citros em três regi?es do Estado de S?o Paulo
Laranjeira, Francisco F;Bergamin Filho, Armando;Amorim, Lilian;Gottwald, Tim R;
Fitopatologia Brasileira , 2004, DOI: 10.1590/S0100-41582004000100009
Abstract: cvc is considered the most important disease of brazilian citrus industry but many aspects of its epidemiology are still unknown. this work aimed to characterize the spatial pattern of cvc affected trees in three regions (northwest, center and south) of s?o paulo state, brazil. three orchards of pêra sweet orange (citrus sinensis) grafted on rangpur lime (citrus limonia) were evaluated twice a month by visual assessments from july 1998 to december 2000. for each evaluation all plants were inspected and assigned as diseased or healthy and cumulative maps were produced. the following analyses were performed: ordinary runs, isopath areas, taylor law, dispersion index and foci structure and dynamics analysis. ordinary runs indicated a trend to randomness. isopath areas analysis showed few compact foci and a trend to uniform incidence in all areas. the other analysis showed few if any differences between regions and results that could classify cvc pattern as slightly aggregated.
Dinamica temporal da popula??o do ácaro Brevipalpus phoenicis e da leprose dos citros sob condi??es naturais de epidemia
Czermainski, Ana B.C.;Bassanezi, Renato B.;Laranjeira, Francisco F.;Amorim, Lilian;
Fitopatologia Brasileira , 2007, DOI: 10.1590/S0100-41582007000400003
Abstract: the density of mite brevipalpus phoenicis, vector of citrus leprosis virus (cilv), is determinant for decisions on control measures for citrus leprosis. little information on the progress of incidence of trees with citrus leprosis has been compiled, either separately or together with the mite population. this study aimed to characterize the temporal growth of b. phoenicis populations and leprosis incidence on citrus trees and the relationship with these populations, under natural conditions. two sweet orange groves, one with 'valencia' and the other with 'natal', were monitored from 2002 to 2004, every 22 days. the increase in disease incidence was slow and estimates of disease growth rate were quite low, varying from 0.0126 to 0.0448 for 'valencia' and from 0.0044 to 0.0525 for 'natal'. the initial inoculum quantity on the branches increased significantly from one cycle to the next. after the three years of observation, the incidence reached 32% in valencia and 6.8% in natal trees. although not systemic, citrus leprosis has a polyetic performance, building up inoculum year after year, especially on the branches. the incidence was not correlated with the mite density on the trees in previous data collections, but presented a significant positive correlation (p<0.001) with the disease incidence reported earlier. this indicates that the presence of symptoms, rather than only the mites, must be taken into consideration in sampling aiming at disease control.
Distribui??o espacial da meleira do mamoeiro em zonas de trópico úmido e trópico semi-árido
Vidal, Carlos A.;Laranjeira, Francisco F.;Nascimento, Ant?nio S.;Habibe, Tuffi C.;
Fitopatologia Brasileira , 2004, DOI: 10.1590/S0100-41582004000300006
Abstract: papaya sticky disease (psd) is caused by a whitefly-borne virus and is one of the most important problems of the papaya (carica papaya) industry in brazil, causing yield losses of up to 100%. in order to better understand its epidemiology and generate data for studies on influence of cultural practices and bioecological features on disease dynamics, 15 papaya orchards were evaluated in eunápolis, bahia (rain forest region) and petrolina, pernambuco (semi arid tropics) between january 2000 and march 2001. the areas were mapped taking into consideration the row or column position of each plant and its disease status. a given plant was considered diseased when it's fruits showed latex exudation, fluid latex and latex spots. the maps were analised by ordinary runs, dispersion index, taylor law fitting and isopath areas. results showed greater aggregation within rows than across rows which can be the consequence of a vector limited movement, with a trend to colonizing nearest plants; the dispersion index indicated a medium to strong aggregation within sub areas and this result was confirmed by taylor law fitting. in most of the areas, higher disease incidence was detected at orchard edges. this may indicate that vector migration can assume important role in psd virus dissemination. in some cases it was possible to detect the presence of isolated foci inside orchards, an indication of vector colony formation and plant to plant transmission from secondary inoculum. significant differences were not observed between rain forest and semi-arid regions.
Dinamica temporal da Clorose Variegada dos Citros em três regi?es do Estado de S?o Paulo
Laranjeira, Francisco F.;Bergamin Filho, Armando;Amorim, Lilian;Berger, Richard;Gottwald, Tim R.;
Fitopatologia Brasileira , 2003, DOI: 10.1590/S0100-41582003000500003
Abstract: this study aimed to discover if the incidence differences between three regions in the state of s?o paulo, brazil could be related to different dynamics of citrus variegated chlorosis (cvc) progress. three areas of the state (northwest, center and south) were evaluated by visual assessments performed two times a month for two years. for each evaluation all plants were inspected and designated as diseased or healthy. nine models were fit to each cvc progress curve, and three were fit to segments of original curves. also, first and second derivatives were estimated for each curve. a good fit was obtained for segments of original curves. first and second derivatives showed many peaks over time. most of those peaks occurred during the spring and summer months. our hypothesis is that derivative peaks are related to flush emission peaks, considering that new sprouts are the preferred feed sites of xylella fastidiosa vectors.
Comportamento sazonal da clorose variegada dos citros em três regi?es do Estado de S?o Paulo
Laranjeira, Francisco F.;Bergamin Filho, Armando;Amorim, Lilian;Lopes, Jo?o Roberto S.;
Fitopatologia Brasileira , 2003, DOI: 10.1590/S0100-41582003000600009
Abstract: this work was to characterize the evolution of citrus variegated chlorosis (cvc) related variables in plants of three regions in the state of s?o paulo (northeast, center and south), in order to demonstrate differences in seasonal pattern of the pathogen, xylella fastidiosa, vectors (sharpshooters), host [sweet orange (citrus sinensis) 'pera' grafted on rangpur lime (citrus limonia)] and disease. twenty symptomatic plants were evaluated monthly from december 1998 to december 2000. the following variables were measured: number of new flushes (nf), percentage of symptomatic branches (psb), percentage of infected assymptomatic branches (piab), percentage of infected branches (pib), estimation of bacteria concentration (ebc), lower and higher temperatures, rain fall and number of sharpshooters in yellow traps. the correlations among variables were tested by distributed lag analysis and the comparison between regions and season was performed by kruskal-wallis and friedman anova and nemenyi test (p<0,005). the cvc related variables (psb, piab, pib and ebc) showed seasonal patterns but no statistical differences were detected among seasons. the northeast orchard showed the highest number of new flushes and percentage of symptomatic branches. the south orchard had the higher percentage of assymptomatic infected branches. there were no statistical differences among regions regarding the concentration of xylella.
Perdas causadas pela ferrugem-asiática em cultivares de soja semeadas em diferentes épocas, no Oeste da Bahia Yield loss caused by rust in soybean cultivars sown in different periods in the western region of Bahia, Brazil
Thyane V. da Cruz,Clovis P. Peixoto,M?nica C. Martins,Francisco F. Laranjeira
Tropical Plant Pathology , 2012, DOI: 10.1590/s1982-56762012000400004
Abstract: Este trabalho teve como objetivo quantificar os danos causados pela ferrugem-asiática em três cultivares de soja, semeadas em diferentes épocas, na regi o Oeste da Bahia. Os experimentos foram instalados no município de S o Desidério, BA, nas safras 2007/2008 e 2008/2009. O delineamento experimental foi em blocos casualizados com quatro repeti es, no esquema de parcelas subdivididas no espa o. A parcela foi representada pelos tratamentos de controle da ferrugem (com ou sem aplica o de fungicida) e as subparcelas foram representadas pelas cultivares (Monsoy 8411, BRS Corisco e BRS Barreiras). Avaliou-se a severidade da ferrugem para o cálculo da área abaixo da curva de progresso da doen a padronizada (AACPDp), o número de folhas ao longo do ciclo e a produtividade de gr os. O modelo logístico foi o que melhor se ajustou aos dados da severidade. A varia o temporal do número de folhas foi ajustada pela fun o polinomial exponencial Ln (y) = a + bx1,5 + cx0,5. As médias da AACPDp e a da produtividade foram comparadas pelo teste de Tukey a 5% de probabilidade. Os danos causados pela ferrugem-asiática da soja na regi o foram potencializados na época de semeadura tardia, ocorrendo desfolha antecipada e redu o na produtividade de gr os. The objective of this work was to quantify the yield loss caused by Asian soybean rust in three cultivars sown in different periods in the western region of Bahia. The experiments were installed in S o Desidério, BA, in the growing seasons 2007/2008 and 2008/2009. The experimental design was carried out in random blocks with four replicates and subdivided plot scheme in time. The plot was represented by the rust control treatments (with and without chemical control) and the subplots represented by cultivars (Monsoy 8411, BRS Corisco and BRS Barreiras). The severity, number of leaves throughout the cycle and yield were evaluated. The logistic model was the one that better fitted the severity data whereas the polynominal exponential function Ln (y) = a + bx1, 5 + cx0,5 fitted the temporal variation of number of leaves better. The means of the area under the disease progress curve and yield were compared by Tukey test. Yield loss increased during later sowing periods due to greater inoculum pressure hindering disease control and decreasing grain yield.
Dinamica espacial da clorose variegada dos citros em três regi es do Estado de S o Paulo
Laranjeira Francisco F,Bergamin Filho Armando,Amorim Lilian,Gottwald Tim R
Fitopatologia Brasileira , 2004,
Abstract: A Clorose Variegada dos Citros (CVC) tem sido considerada a mais importante doen a citrícola no Brasil, mas diversos aspectos de sua epidemiologia ainda n o s o bem conhecidos. O presente trabalho objetivou estudar o arranjo espacial das plantas afetadas, visando caracterizar a dinamica da doen a em três regi es do Estado de S o Paulo (Noroeste, Centro e Sul). Por meio de avalia o de sintomas visuais, foram mapeados, quinzenalmente, três talh es de laranja-doce (Citrus sinensis) Pêra enxertada em lim o Cravo (Citrus limonia), em três regi es do Estado de S o Paulo, desde julho de 1998 até dezembro de 2000. Para o estudo da dinamica espacial, foram aplicadas as seguintes análises: seqüências ordinárias; áreas isópatas; lei de Taylor modificada; índice de dispers o e análise de dinamica e estrutura de focos. As seqüências ordinárias indicaram uma tendência à aleatoriedade na maioria das avalia es, indicando baixa transmiss o a plantas imediatamente vizinhas. A análise de áreas isópatas mostrou pouca forma o de focos compactos, numa tendência à uniformidade da incidência da CVC. As demais análises demonstraram pouca diferen a no padr o espacial da doen a entre as regi es, que pode ser considerado levemente agregado.
Comportamento sazonal da clorose variegada dos citros em três regi es do Estado de S o Paulo
Laranjeira Francisco F.,Bergamin Filho Armando,Amorim Lilian,Lopes Jo?o Roberto S.
Fitopatologia Brasileira , 2003,
Abstract: Caracterizou-se a evolu o de variáveis relacionadas à clorose variegada dos citros em plantas de três regi es do Estado de S o Paulo (Noroeste, Centro e Sul), visando determinar diferen as no padr o sazonal do patógeno, dos vetores, do hospedeiro e da doen a. Foram avaliadas mensalmente 20 plantas sintomáticas em talh es de laranja (Citrus sinensis) 'Pêra' enxertada em lim o (Citrus limonia) 'Cravo', em três regi es do Estado de S o Paulo, no período de dezembro de 1998 a dezembro de 2000, utilizando-se as seguintes variáveis: número de brota es novas (bn); percentagem de ramos sintomáticos (prs); percentagem de ramos assintomáticos infetados (prai); percentagem total de ramos infetados (ptri) e estimativa de concentra o bacteriana (ecb). Em cada regi o foram obtidas as variáveis temperatura mínima, temperatura máxima, precipita o pluviométrica e número de cigarrinhas capturadas em armadilha amarela. Para a determina o de correla o entre variáveis, utilizou-se a análise de Lags Distribuídos e para a compara o de regi es e esta es do ano, a análise de Kruskal-Wallis, Friedman e o teste de Nemenyi (p<0,005). As variáveis relacionadas à doen a (prs, prai, ptri e ecb) apresentaram padr es sazonais, mas n o se observou diferen a estatística entre as esta es do ano. O pomar da Regi o Noroeste apresentou maior quantidade de brota es novas e maior quantidade de ramos sintomáticos. O pomar da Regi o Sul apresentou maior quantidade de ramos com infec o assintomática. N o houve diferen a de concentra o bacteriana entre os pomares das três regi es.
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