Division of Entomology and Nematology, Indian Institute of Horticultural Research, Hessaraghatta Lake Post, Bangalore-560 089 (India).
Studies were conducted on the spatial distribution pattern and sampling plan for the ber (Zizyphus mauritiana Lamark) leaf thrips, Florithrips traegardhi Trybam during 1991–92 at the Indian Institute of Horticultural Research, Hessaraghatta, Bangalore. The dispersion indices, viz., variance mean ratio, mean crowding, Llyod's index of patchiness, Iwao's patchiness regression, and Taylor's power law (b) revealed aggregation among individual thrips and also among loose colonies of the thrips on ber leaves. Finally, the data subjected to the distribution analysis revealed that the thrips followed negative binomial distribution pattern on new leaves within the ber tree. However, the probability of fit vary from tree to tree and year to year depending upon the changes in population density. Sampling plan suggests selection of 25 fresh terminal shoots (4–5 cm size)/tree from all directions within middle canopy. To normalize the population counts Log (x + 1), Log (x + b/2) and Log [log (x + 2)] transformations were found effective.
