Spatial Distribution Pattern of Cotton Leafhopper, Amrasca biguttula (Ishida) (Homoptera: Cicadellidae)

The spatial distribution pattern of cotton leafhopper, Amrasca biguttula (Ishida) was studied under field conditions during 2000 and 2001 at Suwan Farm, Pak Chong, Nakon Ratchasima, Northeastern Thailand. The cotton varieties/lines: Sri Samrong 60 (the recommended variety), Sarid1 and new mutant lines AP1 and AP2 were used in the experiments employing Randomized Complete Block design with 4 replications. The results of both seasons showed that the distribution of A. biguttula was clumped for all varieties/lines and degree of aggregation considerably changed during the generations, as indicated by the values of variance to mean ratio (s 2/ x), negative binomial parameter (k) and the index of aggregation (Iδ). The results of distribution analysis were used to estimate a given sample size and precision level of cotton leafhopper. The appropriate sample size of maximum 10 and 30 plants could be required at low and high aggregation levels of A. biguttula, respectively.