A sampling plan for Bemisia tabaci (Gennadius) population on bt cotton

A sampling plan based on temporal distribution within the plant and dispersion within the field was developed for whitefly, Bemisia tabaci (Gennadius) on Bt cotton hybrid, Ankur 3028 BG II. Counts of B. tabaci adults were recorded at different timings during the day and from three canopies of a plant. The weekly data recorded during the season recorded peak population of B. tabaci adults during second fortnight of July and first fortnight of September. The dispersion of B. tabaci adults was of uniform type. Further, it was determined that 3 leaves from lower canopy of 4 plants in a field were adequate for estimating the precise population of B. tabaci adult on Bt cotton in the whole season. Whereas during peak periods of activity population counts from 3 lower canopy leaves of 3 plants during first fortnight of July (first peak) and 4 lower canopy leaves of 3 plants during first fortnight of September formed the best sampling protocol for estimation of whitefly adults. Sampling should be done from upper canopy at 8–10 a.m. and from lower canopy at 12-2 p.m. and 4–6 p.m.