Population Trends of Sucking Pest on Various Cotton Varieties under Field Condition

Sucking insect pests pose a major threat to cotton productivity by damaging foliage and reducing yield. This study aimed to assess the population trends of Thrips tabaci, Amrasca biguttula, and Bemisia tabaci on different cotton varieties under field conditions, and to evaluate the influence of weather factors to identify resistant varieties for integrated pest management (IPM). Four cotton varieties i.e., Koonj, Bakhtawar, Sindh-1, and Sami were sown during the kharif season using a randomized complete block design (RCBD) with three replications. Weekly pest observations were recorded by randomly selecting ten plants per variety and examining five leaves per plant (top, middle, and bottom). Data on weather parameters were collected from the Meteorological Institute, Agriculture Research Center, Tandojam. Results revealed significant differences in pest populations among the varieties. The population of all pests increased gradually, peaking in mid-July, followed by a decline toward early August. T. tabaci populations peaked between late June and mid-July, with the highest infestation observed on Koonj (12.06±0.21) and Bakhtawar (12.00±0.45), while Sindh-1 maintained consistently lower populations. A sharp decline in thrips density was recorded after mid-July across all varieties, with Sindh-1 showing the lowest final count (0.16 ± 0.68), indicating its potential resistance. A similar trend was observed for A. biguttula and B. tabaci, where Koonj and Bakhtawar recorded higher infestations (3.15±0.35, 3.05±0.30) (4.90±0.51, 5.00±0.53), and Sindh-1 showed comparatively lower pest population (1.00±0.07, 1.30±0.19). overall, Koonj and Bakhtawar recorded the highest pest densities, while Sindh-1 consistently showed the lowest populations of all three sucking pests, indicating its relative tolerance. Sami maintained intermediate pest densities across all species. Correlation analysis revealed that temperature had a significant positive relationship with pest abundance, especially for B. tabaci (r = 0.715, P < 0.001), followed by T. tabaci (r = 0.5, P < 0.001) and A. biguttula (r = 0.348, P < 0.001). This indicates that higher temperatures favoured an increase in pest populations. Relative humidity was negatively correlated with pest populations. Wind velocity had no significant effect. These findings highlight the importance of varietal resistance and climatic factors in pest population dynamics and support the inclusion of resistant varieties like Sindh-1 in integrated pest management (IPM) programs.