Spatial distribution, sampling plan and appropriate transformation for the mango hopper, Idioscopus niveosparsus (Lethierry) (Homoptera: Cicadellidae).
Tandon P. L., Verghese A., Rao G. S. R.
Author Affiliation: Indian Institute of Horticultural Research, Hessaraghatta, Bangalore 560089, India.
Giornale Italiano di Entomologia 4 : 235-242
Abstract : The spatial distribution of nymphs of Idioscopus niveosparsus on mango was studied in Karnataka, India, in 1986 to determine a sampling plan for the pest. Nymphs were aggregated on the mango panicles; the distribution was best explained by S. Iwao's patchiness regression which showed that mean colony size was fixed and that colonies followed a negative binomial series. The optimum sample size recommended was 59 panicles/tree for damage assessment and control studies, and 98 panicles/tree for ecological studies when greater precision was required. There were no significant differences in the distribution of nymphs between the north, south, east or west portions of the tree or between the upper and lower canopies indicating that sampling can be conducted from any point on the tree. The 2 best transformations appropriate to stabilize the variance of the nymphal population were log(x + k/2) and log[log(x + 2)] (r = 0.037 and 0.055, resp.).