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Studies on the Larval Spatial Pattern of Distribution and Sequential Sampling Technique for Cotton Bollworm in Seed Plots of Flue-cured Tobacco

Hua Baozhen; Yuan Feng; Hu Xiaoping(Dept. of plant protection, Northwestern Agricultural University)  
The cotton bollworm, Helicoverpa armigera (HUbner), is a serious pest in the seed plots of flue-cured tobacco in Bac n, Shaanxi province. It damages the flower and capsule,and cause yield loss. The investigation in the early September 1993 shows that the larval spatial patterns of distribution fits both poisson and Negative Binomial, and changes with its mean density. But they all conform to Taylor's power law,S2 = 1. 07523m0. 9931If the economic threshold (m0) is given as 0. 15 larva per plant, the Iwao's sequential sampling technique would be with the maximum sampling size of 16 plants. Having compared the different fixed-sample-size techniques, we conclude that the parallel lines technique is among the best.
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