Within-Plant Distribution and Sampling of Single and Mixed Infestations of Bemisia tabaci and Trialeurodes vaporariorum (Homoptera: Aleyrodidae) in Winter Tomato Crops

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Abstract:

In several areas of Spain, the greenhouse whitefly, Trialeurodes vaporariorum (Westwood), and the sweet potato whitefly, Bemisia tabaci (Gennadius), coexist in tomato, Lycopersicon esculentum Miller. For integrated pest management decision-making, it is important to know the abundance of each species, because they exhibit different abilities to transmit viruses, are susceptible to different biological control agents, and have different responses to insecticides. This study was conducted to provide information on the vertical distribution of T. vaporariorum and B. tabaci in tomato plants grown in greenhouses in winter and to determine the optimal sampling unit and the sample size for estimating egg and nymphal densities of both whitefly species. Eggs of T. vaporariorum were mainly located on the top stratum of the plant, whereas B. tabaci eggs were mainly found on the middle stratum. Nymphs of both species mainly concentrated in the bottom stratum of the plant. When pest abundance and low relative variation were considered, the bottom stratum was selected as the most convenient for sampling nymphs of both whitefly species. Conversely, the same two criteria indicated that either the top or the middle strata could be used when sampling T. vaporariorum and B. tabaci eggs. Several different sampling units were compared to optimize the estimation of nymphal and egg densities in terms of cost efficiency. One disk (1.15 cm in diameter) per leaflet collected from the top stratum of the tomato plant was the most efficient sampling unit for simultaneously estimating the egg densities of the two whitefly species.



RESUMEN En diferentes zonas de España, las moscas blancas Trialeurodes vaporariorum (Westwood) y Bemisia tabaci (Gennadius) coexisten en los cultivos de tomate, Lycopersicon esculentum Miller. Para tomar decisiones en los programas de control integrado de plagas, es importante conocer la abundancia de cada especie ya que tienen distinta capacidad de transmitir virus, son susceptibles a diferentes agentes de control biológico y tienen diferente respuesta a los insecticidas. Este estudio se realizó para obtener información sobre la distribución vertical de T. vaporariorum y B. tabaci en plantas de tomate de cultivos de invierno bajo invernadero, y para determinar la unidad de muestreo óptima y el tamaño de muestra necesario para estimar las densidades de huevos y larvas de estas dos moscas blancas. Los huevos de T. vaporariorum se localizaron mayoritariamente en el estrato superior de la planta, mientras que los de B. tabaci se encontraron principalmente en el estrato medio. Las larvas de ambas especies se concentraron mayoritariamente en el estrato inferior. El estrato inferior de la planta resultó idóneo para el muestreo de larvas de ambas especies de mosca blanca mientras que el muestreo de huevos de T. vaporariorum y B. tabaci podrían hacerse tanto en el estrato superior como el medio. Al comparar las diferentes unidades de muestreo para optimizar la estimación de las densidades de huevos y larvas teniendo en cuenta la relación coste-eficiencia, concluimos que un disco cortado de un foliolo del estrato superior es la mejor unidad de muestreo para estimar simultáneamente las densidades de huevos de ambas especies de mosca blanca.



Bemisia tabaci, Trialeurodes vaporariorum, within-plant distribution, sampling, tomato

Document Type: Research Article

DOI: http://dx.doi.org/10.1603/0022-0493-99.2.331

Publication date: April 1, 2006

More about this publication?
  • Journal of Economic Entomology is published bimonthly in February, April, June, August, October, and December. The journal publishes articles on the economic significance of insects and is divided into the following sections: apiculture & social insects; arthropods in relation to plant disease; forum; insecticide resistance and resistance management; ecotoxicology; biological and microbial control; ecology and behavior; sampling and biostatistics; household and structural insects; medical entomology; molecular entomology; veterinary entomology; forest entomology; horticultural entomology; field and forage crops, and small grains; stored-product; commodity treatment and quarantine entomology; and plant resistance. In addition to research papers, Journal of Economic Entomology publishes Letters to the Editor, interpretive articles in a Forum section, Short Communications, Rapid Communications, and Book Reviews.
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