Weather-Driven Dynamics of Sucking Pests and Natural Enemies in Bt Cotton in the Semi-Arid Region of Rajasthan

A higher number and diversity of sucking pests were observed during the vegetative cotton growth stage (60 days after sowing), declining as the crop matured. A study conducted for 2 years to monitor the dynamics of the major sucking pests (Aphid, Aphis goosypi , Jassid, Amrasca devastans Whitefly, Bemisia tabaci ; and Thrips, Thrips tabaci ) and a reasonably good number of predatory arthropods, including coccinellids, lacewings, and spiders, were found actively preying on the major sucking pest complex of the cotton crop during the early vegetative growth stage. Pest populations commenced in the 34th SMW, peaking in October: aphids (25–30/ 3 leaves, 42nd SMW), jassid (31–33/ 3 leaves, 43-44th SMW), thrips (33–35/ 3 leaves, 42nd SMW), whiteflies (37–42/ 3 leaves, 44-45th SMW). Natural enemies peaked similarly (e.g., coccinellids 4.8–4.9/ plant, 41-42nd SMW, spiders 2.56–2.48 per plant, 41st − 42nd SMW, lacewing 3.64–4.80 per plant, 42nd SMW). Multiple linear regression analyses showed mean weekly weather at one- or two-week lag periods had a significant impact on sucking pest population (aphid, jassid, cotton, thrips and whitefly) fluctuation. Multiple regressions quantified significant positive associations with maximum temperature and sunshine hours, negative with relative humidity for pests and predators. The study highlights warm, dry conditions driving outbreaks, positioning natural enemies as key IPM components in Bt cotton. Therefore, timely monitoring and need-based management interventions during 34th − 45th SMW, aligned with prevailing weather conditions and conservation of natural enemies, are strongly recommended for effective and sustainable pest regulation in Bt cotton.