G. it. Ent., 4 (22): 235-242
August 31, 1989
Spatial distribution, sampling plan and
appropriate transformation for the
mango hopper, Idioscopus niveosparsus (Lethierry)
(Homoptera: Cicadellidae)
by
P. L. TANDON, ABRAHAM VERGHESE, G. S. PRASADA RAO
Abstract - Basic ecological studies were carried out on the nymphs of Idioscopus niveosparsus (Leth.), a serious pest of mango, at the Experimental Station, Hessaraghatta, of the Indian Institute of Horticultural research, Bangalore. Various distribution parameters showed that hoppers followed an aggregation pattern on mango panicles. The distribution was best explained by Iwao's patchiness regression (α = 4.714, β = 1.302) which showed that mean colony size was fixed, and colonies fitted a negative binomial series. The optimum sample size recommended, from this study, was 59 panicles/tree for damage assessment and control studies, and 98 panicles/tree when greater precision is required. Though, the average sample size based on Iwao's α and β values was higher (146 panicles/tree); it is logically better when more precision is needed. As the different sections of the tree viz., the four directions (north, south, east and west) and upper and lower canopies, showed no significant differences in mean densities, sampling can be done from anywhere on the tree, preferably from lower canopy as it is convenient and time saving. Transformations were found appropriate to stabilize the variance of hopper population.
