Spatial distribution pattern of onion thrips, Thrips tabaci on asparagus (Asparagus officinalis L.) and sample sizes necessary for estimating its population density
2004
Asai, M. (Hiroshima-ken. Agricultural Experiment Station, Higashihiroshima (Japan)) | Hoshino, S.
1 . The spatial distribution pattern of adults and larvae of T. tabaci on Asparagus were analyzed by applying Iwao's m-m regression method (1968), which is highly concentrated on either plants or spears on Asparagus. 2 . Sample sizes necessary for estimating the thrips density were calculated from the relationship between crowding and mean density by applying Iwao and Kuno's method (1971). 1) Plants a) Adult: N1 =6.00+24.00/X1 (N1: the necessary number of plants was required to estimate the mean density of adult with a precision in term of D=0.3 (D : magnitude of standard error relative to mean density), X1: the mean density of adults on plant) b) Larva: N2=3.67+14.00/X2 (N2: the necessary number of plants was required to estimate the mean density of larva with a precision in term of D=0.3, X2: the mean density of larvae on plant) 2 ) Spears a) Adult: N3=5.00+8.78/X3 (N3: the necessary number of spears was required to estimate the mean density of adult with a precision in term of D=0.3, X3: the mean density of adults on spear) b) Larva: N4=7.22+2.22/X4 (N4: the necessary number of spears required to estimate the mean density of larva with a precision in term of D=0.3, X4: the mean density of larvae on spear) 3 . In the case of low infestation such as 2 adults per plant, the necessary sample size were concluded to be 18.
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