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1.
Exp Appl Acarol ; 66(4): 491-508, 2015 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-26021609

RESUMO

Brevipalpus phoenicis (Geijskes) is a cosmopolitan and polyphagous mite that transmits important phytoviruses, such as coffee ringspot virus, passion fruit green spot virus and Citrus leprosis virus C. To characterise the dynamics of the probability and the rate of B. phoenicis infestation in response to edaphic and climatic factors, monthly inspections were performed in nine orchards in a citrus region of the State of Bahia, Brazil, for 35 months. Three fruits per plant were examined using a magnifying glass (10×) on 21 plants distributed along a "W"-shaped path in each orchard. Meteorological data were collected from a conventional station. To determine the correlations among the climatic variables, the data were analysed using Spearman correlations. Variables were selected by principal component analysis, and those that contributed the most to differentiate the groups were evaluated via a Mann-Whitney test. Using the quantile-quantile method, the limit values for the following climatic variables were determined: temperature (24.5 °C), photoperiod (12 h), relative humidity (83%), evapotranspiration (71 mm) and rainy days (14 days). The combination of longer days, higher temperatures, lower relative humidity levels and lower evapotranspiration increased the probability of B. phoenicis infestation, whereas successive rain events decreased that risk. Infestation rates were negatively affected by relative humidity levels above 83% and were positively affected by a decreasing available soil-water fraction and increasing insolation and photoperiod.


Assuntos
Ácaros e Carrapatos/fisiologia , Clima , Solo/química , Animais , Brasil , Citrus/crescimento & desenvolvimento , Cadeia Alimentar , Dinâmica Populacional
2.
Ciênc. rural ; 39(3): 896-899, maio-jun. 2009. ilus, tab
Artigo em Português | LILACS | ID: lil-514095

RESUMO

O Recôncavo da Bahia é uma região de clima propício à mancha graxa dos citros (Mycosphaerella citri), doença nunca antes estudada no Brasil. Os objetivos deste trabalho foram definir o tamanho mínimo de amostra para quantificar a incidência, caracterizar os sintomas da doença e elaborar uma escala diagramática para a avaliação de sua severidade. A partir de uma amostragem piloto realizada por avaliação de cinco folhas por quadrante, quatro quadrantes por planta e 30 plantas em cada um dos 10 pomares visitados no município de Cruz das Almas, foi determinado que o tamanho mínimo da amostra em quadrantes e folhas seria de quatro e 16 plantas, respectivamente. De 320 folhas coletadas de diferentes plantas em 11 pomares, foi constatada uma grande quantidade de lesões (média de 131) por folha sintomática, em sua maioria diminutas (média de 0,014cm²). A severidade variou de 0,15 por cento a 35,85 por cento, com média de 7,3 por cento. Com base na severidade real em campo, foi elaborada uma escala diagramática com seis níveis: 1 por cento, 2 por cento, 5 por cento, 9 por cento, 18 por cento e 36 por cento de área foliar lesionada. Cinqüenta imagens de folhas foram submetidas a avaliadores por duas vezes, os quais estimaram a severidade com e sem a utilização da escala, constatando-se um discreto benefício no grau de precisão e de acurácia das estimativas com o uso da escala.


Weather conditions make the Recôncavo Region in the State of Bahia, a favorable region to the occurrence of citrus greasy spot (Mycosphaerella citri), a disease that hadn't been studied before in Brazil. Thus, this research aimed to develop a sampling method to quantify its incidence, to characterize its symptoms, and to develop a diagrammatic scale for assessing disease severity. The minimum sample size to estimate greasy spot incidence in leaves (16 plants) was calculated based on a prospective sampling of five leaves per quadrant, four quadrants per tree, and 30 trees per grove, in ten groves. From 320 mature leaves collected in different plants of 11 groves, it was observed a high number of lesions per symptomatic leaf (mean of 131±102), most of them small (mean of 0.014±.,011cm²). Greasy spot severity varied from 0,15 percent to 35,85 percent, with a mean of 7,3 percent. Based on those severity values, a six level (1 percent, 2 percent, 5 percent, 9 percent, 18 percent e 36 percent of lesioned leaf area) diagrammatic scale was developed. 50 images of symptomatic leaves were showed to evaluators, which estimated the severity with and without the use of the scale. The diagrammatic scale use, slightly increased the estimates accuracy and precision.

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