ABSTRACT
The determination of the spatial distribution of a pest is the first step in the establishment of a sampling plan, as sampling methods are contingent upon the type of spatial distribution of the specific pest studied, varying according to the number and size of samples in the area. This work aimed to study the spatial distribution of soybean plants infested with Bemisia tabaci, under field conditions, through the determination of the aggregation indices and the chi-square test of fitness to the main types of theoretical frequency distributions. The average percentage of whitefly (B. tabaci) infestation increasing after the V1 stage, reaching the maximum infestation of 60.3% in the R1 stage. At the R2 stage, the percentage of infestation ranged from 20 to 40%. According to the models of theoretical distributions studied, the Poisson distribution best defines the distribution of the whitefly.(AU)
A determinação do arranjo espacial da praga torna-se o primeiro passo para o estabelecimento de um plano de amostragem, pois, conforme o tipo de distribuição espacial da praga específica estudada, será necessário utilizar diferentes métodos de amostragem, variando o número e o tamanho da amostra na área. O presente trabalho objetivou estudar a distribuição espacial das plantas infestadas por Bemisia tabaci em condições de campo, na cultura da soja, por meio da determinação dos índices de agregação e dos testes de qui-quadrado de aderência para os principais tipos de distribuições teóricas de frequência. Os resultados mostraram que a porcentagem média de infestação da mosca-branca (B. tabaci) foi aumentando a partir do estádio V1, atingindo a máxima infestação de 60,3% no estádio R1. A partir do estádio R2, a porcentagem de infestação variou entre 20% e 40%. Os modelos de distribuições teóricas estudados indicam que o modelo poisson é o que melhor define a distribuição da mosca-branca.(AU)
Subject(s)
Glycine max , Agricultural Pests , Hemiptera , Residence CharacteristicsABSTRACT
The specimen distribution pattern of a species can be used to characterise a population of interest and also provides area-specific guidance for pest management and control. In the municipality of Dracena, in the state of São Paulo, we analysed 5,889 Lutzomyia longipalpis specimens collected from the peridomiciles of 14 houses in a sector where American visceral leishmaniasis (AVL) is transmitted to humans and dogs. The goal was to analyse the dispersion and a theoretical fitting of the species occurrence probability. From January-December 2005, samples were collected once per week using CDC light traps that operated for 12-h periods. Each collection was considered a sub-sample and was evaluated monthly. The standardised Morisita index was used as a measure of dispersion. Adherence tests were performed for the log-series distribution. The number of traps was used to adjust the octave plots. The quantity of Lu. longipalpis in the sector was highly aggregated for each month of the year, adhering to a log-series distribution for 11 of the 12 months analysed. A sex-stratified analysis demonstrated a pattern of aggregated dispersion adjusted for each month of the year. The classes and frequencies of the traps in octaves can be employed as indicators for entomological surveillance and AVL control.
Subject(s)
Animals , Dogs , Female , Humans , Male , Mice , Dog Diseases/transmission , Insect Vectors/classification , Leishmaniasis, Visceral/transmission , Psychodidae/classification , Brazil/epidemiology , Dog Diseases/epidemiology , Leishmaniasis, Visceral/epidemiology , Leishmaniasis, Visceral/veterinary , Mice, Inbred CBA , Population Density , Population Dynamics , SeasonsABSTRACT
In order to refine the measure of karyotype asymmetry a new chromosomal parameter of dispersion index is proposed that has the potential to decipher even the minor karyotypic variations, thus permitting further evolutionary gradations to the karyotype asymmetry classes of Stebbins. The higher the dispersion index, the more specialized would be the karyotype. The dispersion index takes into account the variance lor gradual change in chromosome size within a complement vis-a-vis variance for the position of centromere in a karyotypic totality. The dispersion index is calculated as the proportionate measure of centromeric gradient to the coefficient of variation for chromosome length; wherin centromeric gradient = length of median short arm – length of median chromosome. Thus, the three most important karyotypic criteria viz., differences in: absolute chromosome size, position of centromere and relative chromosome size, are all covered in the proposed parameter. The effectiveness of dispersion index has been tested on a plant taxa, Papaver L., where karyomorphological details, nuclear DNA content, and morphotaxonomic parameters have been amply elucidated from an evolutionary stand point. It is hoped that dispersion index would find immense utility in delimiting species interrelationships particularly in the closely related taxa, when applied in conjunction with other systematic parameters.