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Enumerative and Binomial Sampling Plans for Citrus Mealybug (Homoptera: Pseudococcidae) in Citrus Groves

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The spatial distribution of the citrus mealybug, Planococcus citri (Risso) (Homoptera: Pseudococcidae), was studied in citrus groves in northeastern Spain. Constant precision sampling plans were designed for all developmental stages of citrus mealybug under the fruit calyx, for late stages on fruit, and for females on trunks and main branches; more than 66, 286, and 101 data sets, respectively, were collected from nine commercial fields during 1992–1998. Dispersion parameters were determined using Taylor’s power law, giving aggregated spatial patterns for citrus mealybug populations in three locations of the tree sampled. A significant relationship between the number of insects per organ and the percentage of occupied organs was established using either Wilson and Room’s binomial model or Kono and Sugino’s empirical formula. Constant precision (E = 0.25) sampling plans (i.e., enumerative plans) for estimating mean densities were developed using Green’s equation and the two binomial models. For making management decisions, enumerative counts may be less labor-intensive than binomial sampling. Therefore, we recommend enumerative sampling plans for the use in an integrated pest management program in citrus. Required sample sizes for the range of population densities near current management thresholds, in the three plant locations calyx, fruit, and trunk were 50, 110–330, and 30, respectively. Binomial sampling, especially the empirical model, required a higher sample size to achieve equivalent levels of precision.

RESUMEN Se estudió la distribución espacial de Planococcus citri (Risso) (Homoptera: Pseudococcidae) en huertos de cítricos en el noreste de España. Se desarrollaron planes de muestreo con precisión constante para todos los estados dedesarrollo situados debajo del cáliz de los frutos recién cuajados, para los estados desarrollados sobre los frutos y para hembras en el tronco y ramas principales del árbol, mediante 66 muestreos, 286 y 101 muestreos respectivamente, realizados en nueve huertos comerciales durante el periodo comprendido entre los años 1992 y 1998. La dispersión se estudió utilizando la ley potencial de Taylor, dando como resultado que la población de P. citri se distribuye de forma agregada en los tres lugares del árbol muestreados. Utilizando el modelo binomial de Wilson y Room y la fórmula empírica de Kono y Sugino se estableció una relación significativa entre el número de insectos por órgano y el porcentaje de órganos ocupados por algún insecto. Se desarrollaron planes de muestreo para una precisión constante (E = 0.25) para estimar la densidad media de la población utilizando la ecuación de Green y los dos modelos binomiales. Para muestreos de toma de decisión, losmuestreos enumerativos siempre dieron menor tamaño de muestra que los muestreos binomials. Por lo tanto, recomendamos el uso de métodos de muestreo enumerativos para programas de manejo integrado de plagas en cítricos. Los tamaños de muestra requeridos para estimar medias en el rango de densidad de población establecido actualmente como umbral de manejo, para cáliz, fruto y tronco, fueron de 50, 110–330, y 30, respectivamente. Los métodos de muestreo binomiales, especialmente para el modelo empírico, requirieron tamaños de muestra mayores para alcanzar la misma precisión.

Keywords: Planococcus citri; Taylor’s power law; binomial sampling; enumerative sampling

Document Type: Research Article

DOI: http://dx.doi.org/10.1603/0022-0493-99.3.993

Publication date: June 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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