Population dynamics of sucking pests in cotton ecosystem were studied at Tamil Nadu Agricultural University, Coimbatore during winter (2021) and summer (2022) seasons. Weekly observations were recorded on 20 randomly selected plants representing top, middle and bottom canopy of the crop which was raised in regular planting dates of winter and summer and were maintained as per the recommended regular agronomic practices except insect management interventions. During winter season, sucking pests viz., leafhopper, aphids, thrips, and whitefly were first observed in field from 39th SMW i.e. one month after sowing. Mealybugs were first observed during 41st SMW i.e. 43 days after sowing (DAS) of crop. The highest population of leafhopper, aphids, thrips, whitefly and mealybug recorded was 4.7, 18.7, 4.6, 2.45 no. per 3 leaves and 13.7 no. per 3 twigs, respectively. The mean population of sucking pests was high in October, 2021 and coincided with square formation to flowering stage except mealybug, which attained peak during January, at the boll bursting stage of crop. During summer season, the sucking pests were found to colonize from 8th SMW, corresponded to 20 DAS crop, while the mealybug occurred at 11th SMW, 40 DAS crop. The peak population of leafhopper, aphids, thrips, whitefly and mealybug registered was 5.4, 38.4, 4.9, 7.07 no./ 3 leaves and 2.4 no./ 3 twigs, respectively. The mean population of sucking pests was high from mid march to first fortnight of april 2022, and by that time the crop was at square formation to flowering stage. On comparison of both the season, summer season crop was infested by intensive level of sucking pests. Correlation results revealed that maximum temperature (0C) showed positive correlation, whereas rainfall (mm) showed negative correlation with population growth of sucking pests. Results of multiple linear regression analysis revealed that all the weather parameters collectively caused 51.1% – 88.4% influence on the population fluctuation of sucking pests.

Preliminary screening of twenty-nine cotton genotypes (Gossypium hirsutum) against the leafhopper Amrasca biguttula biguttula Ishida undertaken, during August 2019 to February 2020, revealed fifteen genotypes viz., TCH 357, TCH 1809, TCH 1828, TCH 1895, TCH 1897, TCH 1941, TSH 383, TVH 002, TVH 003, TKH 0762, TKH 1225, SVPR 6, CO 15, KC3 and Suraj, as moderately resistant. Selected preliminary screening entries subjected to advanced screening revealed TCH 357, TCH 1809, TCH 1895, TCH 1897, TCH 1941, TCH 1828, TSH 383, TVH 002, TVH 003, TKH 0762, SVPR 6 and CO 15 as moderately resistant with population range of 2.75 to 4.42 numbers per three leaves and KC3 resistant. In the artificial screening, the resistant cultivar KC3 had least leafhoppers (2.67 per plant) and it had 56 trichomes per 300 mm2, which was higher than resistant check NDLH 1938. The resistant genotype KC3 had the maximum phenol (4.3 mg g-1), amino acid (136 mg g-1) and tannin (167 mg g-1), while the susceptible genotype DCH 32 had the lowest amount of total phenol (1.2 mg g-1), amino acids (18 mg g-1) and tannin (40 mg g-1).