Distribution patterns of the bamboo shoot borer, cyrtotrachelus dichrous fairmaire (Coleoptera: Curculionidae)

Attajarusit, J.; Morakote, R.; Nanta, P. . Inst. of Agricultural Technology

Distribution patterns of the bamboo shoot borer, cyrtotrachelus dichrous fairmaire (Coleoptera: Curculionidae)

1997

Attajarusit, J. | Morakote, R. | Nanta, P. (Suranaree University of Technology, Nakhon Ratchasima (Thailand). Inst. of Agricultural Technology)

Study was carried out in 5 years old bamboo (dendrocalamus asper) orchards during the outbreak periods i.e., rainy season (Aug.-Oct.) 1992 and 1993 in Amphoe Pob Phra, Mae Sot and Mae Ramad of Tak Province, Thailand to determine the distribution patterns of bamboo shoot borer (Cytotrachelus dichrous Fairmaire). Determination of a suitable sample size was firstly studied and it was found that at CV (mean) = 20 percent at plant spacing of 6*8 m, a minimum of 80 shoot clumps per experimental plot was the most appropriate sample unit. There were 19 experimental plots, each of 100 shoot clumps or within the area of 92*50 m, use for the counts and records of the undamaged and damaged shoots (i.e. with eggs or with larvae). The counts were done in all young individual shoots of all rows aged during 7-14 days of emergence. There were three distribution patterns tested i.e. the negative binomial (k values), the Poisson (X*[2) values) and binomial (X*[2) values). The result showed that there were 63.2 percent of the total plots were with negative binomial distribution with k values at 95 percent level range of 3.318-0.0012 with 95 percent probability values range of 0.9999-0.0250. There were 26.3 percent and 10.5 percent of the total plots were of Poisson and binomial distributions with the X*[2) values ranges of 8.5249-0.043 (with 95 percent probability values ranged 0.9987-0.17811) and 0.000001-7.8573 (with 95 percent probability values ranged 0.9199-0.0627), respectively. the desired distribution patterns were designated by the highest probability values at 95 percent statistically confident levels. The indicated patterns agreed with the general observation that in early outbreak period (Aug.) most population was of Poisson distribution and when the outbreak was severe (in Sept.), the distribution changed to negative binomial.

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