Annual Report of The Kansai Plant Protection Society
Online ISSN : 1883-6291
Print ISSN : 0387-1002
ISSN-L : 0387-1002
Original Articles
Methodologies for estimating the density of tea spiny whitefly larvae, Aleurocanthus camelliae Kanmiya and Kasai in tea fields
Akihito OzawaToru UchiyamaYukio KosugiHajime Haga
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JOURNAL FREE ACCESS

2017 Volume 59 Pages 21-26

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Abstract

We developed methodologies for estimating the density of the larvae of tea spiny whitefly, Aleurocanthus camelliae Kanmiya and Kasai, in tea fields. In the period of rising density in 2013, 100 tea leaves were collected from each of 50 commercial tea fields in Shizuoka Prefecture, and the number of larvae and emerged exuviae of A. camelliae on the leaves was counted. Since a high correlation of R2 = 0.98 or 0.99 was consistently found between the true larval density and apparent larval density, including emerged exuviae, from February–July 2013, the apparent larval density was used as a surrogate for true larval density in subsequent analyses. There was a significant correlation between larval density and the frequency of leaves infested by larvae, and this relationship was well described by the Kono and Sugino (1958) formula. Based on the resulting regression equation, we showed that the frequencies of leaves infested by the larvae corresponded to several steps of densities, assuming a standard value of the degree of occurrence of the pest. A significant positive correlation was found between mean density and mean crowding index in each field. The index of basic contagion α = 8.56 and the density-contagiousness coefficient β = 1.66 were obtained from the regression equation. Based on these values, the relationship between larval density and number of samples required to satisfy aimed precision D was simulated according to a study by Iwao and Kuno (1968). Results showed that, if the larval densities are 0.67, 0.33, and 0.16 or more per leaf, the aimed precision D = 0.3 for the survey is satisfied by sampling 50, 100, and 200 leaves, respectively.

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© 2017 The Kansai Plant Protection Society
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