Population Dynamics of Sucking Pests in Dual Season Cotton Ecosystem and Its Correlation with Weather Factors

Abstract

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.