991 resultados para Seasonal migration
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Thrips can be important pests of capsicum and chilli crops, causing damage through their feeding and by vectoring viral diseases. As different species vary in their ability to transmit viruses and in their susceptibility to insecticides, it is important to know which species are present in a crop. The seasonal occurrence of thrips in capsicum and chilli crops in the Bundaberg district of south-east Queensland was investigated from July 2002 to June 2003. Fifty flowers were collected weekly from crops on seven farms and the adult thrips extracted and identified. Thrips palmi Karny and Frankliniella occidentalis (Pergande) were collected in the greatest numbers, with T. palmi predominant in autumn crops (March to July) and F. occidentalis predominant in spring crops (August to November). Pseudanaphothrips achaetus (Bagnall) was common, while Thrips tabaci Lindeman, Thrips imaginis Bagnall and Frankliniella schultzei (Trybom) were collected in low numbers.
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Alternaria leaf blotch and fruit spot caused by Alternaria spp. cause annual losses to the Australian apple industry. Control options are limited, mainly due to a lack of understanding of the disease cycle. Therefore, this study aimed to determine potential sources of Alternaria spp. inoculum in the orchard and examine their relative contribution throughout the production season. Leaf residue from the orchard floor, canopy leaves, twigs and buds were collected monthly from three apple orchards for two years and examined for the number of spores on their surface. In addition, the effects of climatic factors on spore production dynamics in each plant part were examined. Although all four plant parts tested contributed to the Alternaria inoculum in the orchard, significant higher numbers of spores were obtained from leaf residue than the other plant parts supporting the hypothesis that overwintering of Alternaria spp. occurred mainly in leaf residue and minimally on twigs and buds. The most significant period of spore production on leaf residue occurred from dormancy until bloom and on canopy leaves and twigs during the fruit growth stage. Temperature was the single most significant factor influencing the amount of Alternaria inoculum and rainfall and relative humidity showed strong associations with temperature influencing the spore production dynamics in Australian orchards. The practical implications of this study include the eradication of leaf residue from the orchard floor and sanitation of the canopy after harvest to remove residual spores from the trees.
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Obverse: Emblem of the Israel Government and Medals Corporation. Reverse: A Jerusalem panorama, inscription.
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Obverse: Within a circle (a symbol of the sun) an inscription. Reverse: The emblem of the Israel Government Coins and Medals Corporation, inscription.
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Obverse: Stylized Star of David. Reverse: Emblem of the Israel Government Coins and Medals Corporation.
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Obverse: Emblem of the 25th Anniversary of the State of Israel, menorah and number 25 created by ribbon. Reverse: Emblem of the Israel Government Coins and Medals Corporation.
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Obverse: Stylized Desing of an Israeli Navy ship with rocket coming out of the canon. Reverse: Emblem of the Israel Government coins and Medals Corporation.
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Obverse: In the center stylized number 26. Reverse: The emblem of the Israel Government Coins and Medals Corporation.
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Obverse: In the center stylized inscription. Reverse: Emblem of the Israel Government Coins and Medals Corporation.
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Zoonoses from wildlife threaten global public health. Hendra virus is one of several zoonotic viral diseases that have recently emerged from Pteropus species fruit-bats (flying-foxes). Most hypotheses regarding persistence of Hendra virus within flying-fox populations emphasize horizontal transmission within local populations (colonies) via urine and other secretions, and transmission among colonies via migration. As an alternative hypothesis, we explore the role of recrudescence in persistence of Hendra virus in flying-fox populations via computer simulation using a model that integrates published information on the ecology of flying-foxes, and the ecology and epidemiology of Hendra virus. Simulated infection patterns agree with infection patterns observed in the field and suggest that Hendra virus could be maintained in an isolated flying-fox population indefinitely via periodic recrudescence in a manner indistinguishable from maintenance via periodic immigration of infected individuals. Further, post-recrudescence pulses of infectious flying-foxes provide a plausible basis for the observed seasonal clustering of equine cases. Correct understanding of the infection dynamics of Hendra virus in flying-foxes is fundamental to effectively managing risk of infection in horses and humans. Given the lack of clear empirical evidence on how the virus is maintained within populations, the role of recrudescence merits increased attention.
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Obverse: Emblem of the Israel Government Coins and Medal Corporation. Reverse: Stylized design of the Western Wall and the Mount above.
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Obverse: Emblem of the Israel Government Coins and Medal Corporation. Reverse: The monument to Jewish soldiers erected at the Jewish Martyrs Memorial Institute of Yad Vashem in Jerusalem.
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Obverse: Emblem of the Israel Government Coins and Medal Corporation. Reverse: Stylized menorah, inscription.
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Obverse: emblem of the Israel Government Coins and Medal Corporation. Reverse: Dove with spread wings.