Impact of High-density Planting on Seasonal Incidence of Sucking Pests and Pink Bollworm, Pectinophora gossypiella in Cotton

Abstract

The present investigation on the dynamics of insect pests of cotton under the High-Density Planting System (HDPS) was conducted during Kharif 2024 at the All India Coordinated Research Project (AICRP) on Cotton, Haradanahalli Farm, Chamarajanagar. The study aimed to elucidate the seasonal incidence of major pests and their association with weather parameters. Results revealed distinct interactions between pest incidence, crop growth stages, and prevailing climatic conditions. Among the sucking pests, aphids and leafhoppers appeared during the early crop stages, with populations increasing as the crop advanced. Although overall pest incidence was comparable among the four cotton genotypes evaluated, the non-Bt hybrid ‘Suraj’ exhibited higher susceptibility to sucking pests. Peak infestations of aphids (41.60 per 3 leaves) and whiteflies (3.46 per 3 leaves) occurred during the 35th standard meteorological week (SMW), while leafhoppers (2.42 per 3 leaves) and thrips (6.43 per 3 leaves) reached maxima in the 43rd SMW. Correlation analyses indicated that aphids and whiteflies were positively associated with maximum temperature (r = 0.509–0.741) and negatively correlated with relative humidity and rainfall. Leafhoppers showed positive correlations with maximum temperature (r = 0.244–0.375) and morning relative humidity (r = 0.521–0.739), but negative relationships with minimum temperature and rainfall. Thrips exhibited weak positive associations with temperature and morning humidity, but strong negative relationships with minimum temperature and rainfall. The pink bollworm larval population was strongly negatively correlated with minimum temperature (r = –0.801 to –0.862). Overall, weather factors together accounted for 55–57% of the variation in pest incidence, emphasizing the significant role of temperature, humidity, and rainfall in influencing pest population dynamics under HDPS cotton.